Sunday, February 19, 2017

A Powerlifter’s Guide to Velocity Based Training Pt. 2: The Case for VBT


  • This is a conceptual piece on how velocity based training fits into powerlifting. This is not a collection of tips and tricks. Those practical tips will be in part 3. 
  • Velocity based training can give fairly comprehensive feedback in terms of intensity, fatigue, exertion, and readiness to train.
  • Velocity based training will only work for you if auto-regulation works for you. Auto-regulation may not work for you and/or velocity based training may not work for you.
  • Rather than buying into VBT first, it’s probably better to see if auto-regulatory methods like AMRAPs driving training maxes or the RPE scale works for you. It isn’t the same thing, but aspects of both tie back to VBT.
  • There are gaps in which VBT is not appropriate. Where these gaps may exist, it may be appropriate to use different methods. These include full range tempo reps, reps with multiple concentric and eccentric points, and movements with a high balance component.
Update 2/28/2017: An eccentric VBT article came to my attention. It's not of consequence, but it is worth mentioning. Additions have been made with no changes to other content.
Update 8/17/2017:  I added some content since this article gets a good amount of hits


Force-velocity curve borrowed from Training Principles
 for Power by Haff and Nimphius from this link
from the Strength and Conditioning Journal.
               Velocity based training (VBT) has been around for a long time. Despite that, we haven’t tried to generalize the implications of exercise velocity as many readily do now. Part of that issue is velocity is very specific in a lot of ways, so we can only speak of it in terms that are general in broad strokes but still specific enough for to the athletes we’re working with – and then tack on a bunch of caveats as appropriate for skill level, height, etc.

               VBT is an auto-regulatory style of training that attempts to change variables of training as appropriate for individual athletes according to their readiness to train. The underlying assumption is that force and velocity share a relationship and that different aims of training can be quantified according to ranges of training. I hate starting here since everyone does (I have in the past and hate myself for it), but I feel like I have to. This graph on the left shows what I mean.

               You could also superimpose the power curve over this, but I’d also be obliged to parrot the mantra that powerlifting has little to do with power. Back on target: if powerlifting is all about force output, then we can keep tabs on Force by essentially keeping track of velocity. There have been some generalized charts that every VBT device manufacturer tends to circulate (myself included) showing the F-V curve and defining arbitrary ranges as absolute strength zones, strength-speed zones, etc. These are generalized. There’s a world of difference of what’s bottom end velocity (closer to 1RM and strength) for pulls from the floor and a pull from above. If you go by the orthodoxy, your overhead pull 1RM might never be slow enough to be considered within the absolute strength zone. It’s an easy way to explain VBT, but not necessarily accurate. Here are the generalized training zones of velocity:

Training Quality
Velocity (m/s)
Absolute Strength
Accelerative Strength
0.5 - 0.75
0.75 - 1.0
1 - 1.3
Starting Strength
>1.3 m/s

               I disagree with this chart simply because it doesn’t take into account the floor (minimum velocity threshold) or ceiling of different velocities and usually isn’t accompanied by an acknowledgment that individual experiences may vary. Every load-velocity profile I’ve generated for myself diverges from this chart in at least one training quality. Additionally, enough movements diverge from the category I concern myself with the most: absolute strength. We need to either accept training quality zones in broad guidelines or understand it’s different for everyone and every movement. Strength is specific. Velocity can be used to measure strength. Velocity is specific.
Notice that hypertrophy is not listed in this. Hypertrophy could be considered an ancillary effect to training in the mid to lower velocity/moderate to high intensity. Understanding that this table is a basic principle, we can move on though. We won't ignore hypertrophy as an essential training effect to progress absolute strength, but the fact that something doesn't fit neatly into this table doesn't matter.
               So let’s talk about the general ways we can use velocity, ignoring the table because the table fucking sucks. In the most general terms, a light load moves faster than a heavy load, showing intensity. The first rep in the tank moves faster than the last rep in the tank, showing exertion across a set. And drops in velocity from the first rep in a set across multiple sets at the same weight can show fatigue across a session. Additionally, losing form, tightness, and regaining balance (like getting out of position) tends to be reflected in velocity as a loss. That variance in velocity behavior is essentially variance in performance of the movement. There are caveats to many of these, but that’s generally what VBT does. It quantifies intensity, fatigue, exertion, and to some extent also proficiency. With a good load-velocity profile of the movements you plan to use, you can effectively gauge intensity, fatigue, and exertion - for the most part. Unlike 1RM and multi-rep maxes, this can be used across different time domains for feedback from immediate to trends in the broader mesocycle.
Velocity based training quantifies intensity, fatigue, exertion, and to some extent proficiency/movement quality.


               My first introduction to VBT was through a facility that didn’t use it for powerlifting. I’ve always been interested in it from a powerlifting perspective, but I won’t pretend like that’s how it’s commonly used or what it’s most optimal for. But it does pose some advantage for powerlifting since it’s a different type of feedback. John Grace has written and presented on athlete monitoring systems and he breaks it down well enough that a simple army guy can understand it (I can say that, am army guy) – hell, maybe even a Marine (sorry Cody). All of it comes back to motor development principles of feedback operating on two intersecting continuums: the internal and external, and the objective and subjective.
  • AMRAP - As Many Reps As Possible. Can be used to finish an exercise. From this AMRAP you can calculate an estimated 1RM, which feeds forward into a training max that loading schemes are based off of. Usually planned in the weekly context.
  •  RPE - Rating of Percieved Exertion. Popularized by Mike Tuscherer. A given set can be rated on a 1-10 scale in terms of difficulty and how many repetitions/additional load the lifter felt they could have completed had they gone until failure.
Something that is internal is a feedback variable that is of origin to the athlete, like their heart rate or their rating of perceived exertion. Something that is external is a feedback variable that is of origin outside of the athlete, like their movement velocity or a qualitative assessment after reviewing video (IE: “That squat looked like hot garbage”). Any type of feedback is going to be internal or external as well as objective or subjective. Objective feedback is tied to some universally agreed upon standard, like time, velocity, or some other metric common to all. Subjective feedback is tied to qualitative assessments, opinions, and personal inclinations.

Now that we’ve unnecessarily deconstructed that, here’s how that breaks down according to some examples of auto-regulation methods:

Internal, subjective
External, objective
External, objective
Video review of the set
External, subjective
Rest interval is over after HR returns to X bpm
Internal, objective

               Anyone that’s interested in VBT should probably be interested in auto-regulation first. That said, VBT is only one way to auto-regulate training. If you’ve had success with auto-regulation training, then you might have success with VBT. For example, if you find that increasing your training max by performing an AMRAP at a given intensity both helps upregulate (due to improvement) and downregulate (due to fatigue) your training appropriately, then VBT might work for you. If you find that making judgment calls yourself about the difficulty of your workout, RPE or otherwise, guides training productively by increasing or decreasing training load – then VBT might work for you. If you find yourself diverting frequently from your training plan based on feel, then VBT might work for you. Chances are, it’s better for you to try at least one of those methods first before you try VBT. There is no monetary cost associated with performing an AMRAP or using the RPE system. But there is certainly a cost for adopting VBT. Under sell much?
Auto-regulation training isn’t anything new or fancy. Bro’s have been using auto-regulation for years based purely on how they felt the day of their planned training. The difference is most auto-regulation methods attempt to assign values and utilize quantitative measures to dial in just how much or what factors to regulate. 
               The common argument that people have against VBT is the idea that it will consume your entire training style – which is ridiculous. It’s another tool to improve your performance, not a crutch. It’s not essential, but neither are wrist wraps, and I don’t see people up in arms abo… oh wait, nevermind. You don’t need VBT anymore than you need to video record your top end sets for review – but it sure can be helpful. If you don’t want to use it – don’t. If you haven’t really used it, then what is your criticism worth? Using a device for a week doesn't qualify you to have a worthwhile opinion on the matter. Just sayin.
I forgot we’re in the age of the internet and everything is offensive, including what other people are offended about. I’m not going to attempt to convert anyone on this. This is absolute niche of the niche. We’re talking about one tiny segment of ideologues (VBT proponents) in a barbell sport that struggles to gain recognition as a sport (powerlifting). You could be either of those two and be resented by a good amount of people. If you enjoy resentment/being forever trivial, do both.
               Another thing we have to accept is that VBT is essentially snowflake training. It is based on the assumption that everyone responds differently and adapts differently to different types of stressors in different ways and it affects different factors like different intensities and different volumes and different differences. You can over-fit VBT to your training and individual responses, and it might be meaningful, but it might be a poor investment of time for little gratification. If it helps you make improvements, like improving your 1RMs, increasing your volume, or pulling you back from CNS nullification (I was told doing more than 1 set of 5 deadlifts would fry my CNS /s). The idea of daily estimated 1RM’s fluctuating wildly is probably overstated by VBT proponents. Usually, when I’ve observed that phenomenon, it’s was either obvious before conducting a submaximal test or such a small difference its consequence was minor. That said, if you could get a 5% improvement in your total, why wouldn't you take it? Some folks obsess about nutrition which could have equally small effect size, but for some reason auto-regulation is questionable? 
Where "/s" means sarcasm. Just want to make that clear. If you're trying to transition from StrongLifts to VBT you should probably do a powerlifting program first.
               Like almost every grand idea in powerlifting, you can essentially ask one question and deem relevance. Make gains? If yes=is good. If no=lol STFU. It’s not for everyone, and it might even cause more harm than good – but if it works for you, then it works. It’s not the first crazy, niche thing to come to powerlifting. Hopefully, it’s a step above keto.


               The frequency of feedback is another factor. A simple analogy here is using an AMRAP to adjust your training max. You’re likely going to do an AMRAP once a week to change your loading scheme. That single source of feedback will up or down regulate loading until you conduct another AMRAP. RPE, on the other hand, is readily available. You can access that feedback on the fly: in the middle of a set, after completing a set, after a session, etc. You can also use multiple time domains with that information and shape the training. VBT acts in the same way, depending on the device. Some devices allow you access that feedback within the set, some readily give you useful metrics after the set (percent velocity loss, average set mean velocity change vs previous set, trend analysis, etc), and some cloud services will allow you to view how one day’s performance stacks up against previous days’ performance.

               That frequency of feedback is important to how it shapes training. Normally when we think of training plans, we think of overly thought out planning. It immediately makes me think of this:
Borrowed from Bompa and Haff from Periodization:
Theory and Methodology of Training
               In the powerlifting perspective, this is primarily seen in percent-based training methods, assigning a percentage of 1RM as intensity and varying it with intensity to approach different aims within a training cycle leading up to a competition. I’m not going to rail against periodization in powerlifting though, I’m not Louis Simmons. I'm also not going to try to represent different methods of periodization in powerlifting, but I think a good place to refer anyone to on the subject would be Chad Wesley Smith's Scientific Principles of Strength Training.

Food for thought: a lot of periodization attempts to dissipate fatigue of a training cycle. If  auto-regulation training can control for fatigue, you could get better training economy or have actual factors to determine appropriate cycle length and better 'potentiate' one phase to the next.

               That said, if we use objective feedback to shape how our training plan evolves, our plan becomes more process oriented than it is plan oriented. As a coach of mine used to put it, “We write our plans in pencil.” We’re not completely winging it, but essentially we can complete the volume of work we’re capable of within a session or microcycle at the given intensity that is appropriate given our recovery to ensure we stay on track to accomplish the goals of our tentative plan. If our feedback is only once a week, we can only adjust once a week. If our feedback is more frequent, we can adjust more frequently. However, if we adjust too liberally or accept every variance as a cause for adjustment, we run the risk of over-fitting our training. We can’t afford to miss the forest for the trees, and that is a particular trapping for auto-regulatory training.

               RPE is great to use as an example here because Mike Tuscherer has already developed a thorough system to help recognize the potential trappings of over-relying on feedback. For example, his development of TRAC helps identify those trends through a mix of internal, external, objective, and subjective measures. More simply, looking at previous training logs could do the same thing. There a hundred ways to get broad pictures of how training is developing, VBT provides a window into how training is working fairly immediately. If you want to know if it's worthwhile, you should probably measure it by another metric, like baseline volume, volume by lift, the number of lifts, or one of the million other metrics places like MyStrengthBook track.

               Training is partly process-oriented, and you should strike the iron while it’s hot. Maybe not every time, and probably not always with intensity or volume, but if we fail to capitalize on training opportunities when they present themselves we’re doing just as much as a disservice to ourselves as we would be when training through our low points when we’ve objectively over-reached.



From Supertraining by Siff and Verkhoshansky based on the
data from others listed at the bottom of the pic. This is better
than the F-V curve and you can make the argument that
hypertrophy is the product of strength-endurance
VBT helps give objective feedback on many things, but we should probably give a realistic expectation of where it isn’t best suit or absolutely struggles. One place VBT is not appropriate is isolation movements. Firstly, you might not observe the same velocity relationship in a bicep curl that you do a squat. Concerning the F-V relationship, Siff and Verkhoshansky posited the additional idea of strength-speed-endurance. We can think of strength as force, speed as velocity, and endurance (in powerlifting terms) as reps. In these isolation movements, we’re talking about supporting muscles that could have atypical velocity responses to what we see in a compound movement because their role is more endurance focused – an element we’re not incorporating. That’s an overly complicated reason why you shouldn’t implement VBT with isolations, but the simpler reason is that it’s wasted effort to apply VBT across the board. Adding VBT does add time, but it’s also not worth majoring in the minors here. Additionally, you’ll see weird results for sets of 15+ reps. And by weird I mean unactionable data.

A good rule of thumb to apply here is if there isn't a 1RM, 3 RM, and 5RM for that exercise, it's probably not fruitful to add VBT to it. I say that because for some people and/or some exercises, there are only 1RM's and 6RM's, with no weight inbetween. Velocity operates more reliably in situations when you need to gauge proximity to failure. The less granular points in proximity to failure, the more the relationship of velocity to exertion/intensity falls apart.

For compound movements for several reps, the mechanism that probably screws up the measurement is probably self-selected pacing. If you know 30 reps are coming, you likely won't exert maximum velocity - at least not throughout. This is something you might be able to mentally power through for hypertrophy work or high volume work, but in my experience can be avoided. VBT will give you feedback and you'll be able to see the points where you reset to take your air or reinforced form cues.
Adding VBT to isolation movements isn’t practical or logical. Maybe it’s a selling point of incorporating VBT for recreational lifters by manufacturers, but it doesn’t provide actionable data for powerlifting. Collecting data for the sake of building a data silo makes about as much sense as worrying about how your hair product is going to increase your lifts. But then again, ROM gains? Mullets= legal ROM cheat


Tempo work is an obvious shortcoming for VBT measurement. If you’re doing tempo movements with controlled descents, pauses, and ascents, there’s not much useful data there. If you control the time and the displacement is near the same every time, you’ve controlled velocity as well. Maybe you can identify inconsistencies, but likely no better than you could just by feel or video. Using VBT for tempo work is like using the snatch or clean and jerk for conditioning, it’s the wrong tool for the job.
Update: An article came out in November covering VBT eccentrics. The results did not overwhleming favorable using VBT eccentrics over VBT regulated training for strength. I'm not going to open the can of worms that is ecceentric training, nor am I going to muddy the water with VBT in eccentric training. 
Depending on what device you’re using, paused positions will be fine. For example, paused squats in the hole or bench paused at the chest. A high pause near a sticking point might not work for different devices, but it all depends on device limitations. Most VBT devices output the upward part of the movement in their metrics (mean velocity, peak velocity, power, etc). In the device’s eye, unless it knows how to measure this movement, it might record it as two separate lifts, but will most likely start recording from the first upward movement until the downward movement, skewing that velocity. As much as we want to believe that our pauses are still action, they are milimiters of movement up and down. The actual velocity we would want in this case would be the velocity of each upward movement, but I haven't seen an easily device that does that yet.

There is some evidence that mean propulsive velocity is less appropriate than mean conventric velocity in the bench throw. 

Some devices compensate for this by setting a threshold for reversal (the slight change in direction despite pausing) or velocity. Some devices just can’t detect well under certain velocities, so they terminate the measurement below a threshold (for example, 0.15 m/s) and count any additional movement as a whole other rep. Open Barbell filters out velocity below 0.02 m/s. These numbers and this unnecessarily technical explanation don't have any meaning, though. Just do the movement and see if it’s screwy. If screwy, don’t do-y (with VBT).
Special note on tether devices: There could be some additional limitations, but not many that I feel I impactful. For one, I'm not sure there's an optimal way to tether-track pull ups. Even though there is a way to attach a tether to a barbell lunge, keep in mind that the tether does not compensate for angle of pull (except the $2200 GymAware), so you're likely going to introduce so much anterio-posterior movement to make the measurement meaningless. For a device like Open Barbell, simply attempt to measure out what the vertical bar displacement should be vs the length as measured by the device. Since velocity is displacement by time, the velocity could be off. Regardless though, that movement requires balance, which I added at the bottom.
Two movement types that shouldn't be excluded are movements where the pause happens between a beginning eccentric phase and a concluding concentric phase as well as pauses that occur in the eccentric phase only. This is exactly what describes a competition bench. A study by the Spanish VBT proponents seems to say a pause between the eccentric and concentric increases the reliability of the measurement. An example of pausing during the eccentric phase only would be something like pausing at the high sticking point in the squat on the way down (not on the way up). The explanation for this is more simplistic, as devices generally only measure concentric velocity. The load might be reduced by the intensity of what you're able to accomplish, but the measurement is solid given the minute changes in height don't exceed the device's filtering threshold. I believe Open Barbell's threshold is 2.8 mm based on their wiki, but I suspect it might actually be higher (anecdotal, or I don't understand metric system units of length smaller than a meter).
Gabrielle Tucker has a IG post show what I mean with pauses, and also she's just an amazing lifter you need to be aware of. In this video she has two pauses. One coming directly off the floor, and one right before returning to the floor. In the VBT context, the one coming off the floor would skew things. However, the one returning to the floor would not skew the measurement. Gabbrielle doesn't use VBT but is a world record holder, proving the point that VBT is just a training method, not the only training method.
I'm sort of obliged to ask if pausing concentrically or eccentrically nets the same results from an adaptation standpoint. On one hand, the mechanism could simply be that isometric exercise increases strength in that range of motion, give or take 15 degrees on either side. On the other hand, maybe the important part is the rate of force production from a dead stop in the concentric phase. I'm more inclined to think the main benefit comes from isometric strength effects rather than the accelerative part of the movement, but I'll also admit this is not something I'm well versed in. You could still yield the positive effects of acclerating from a dead stop with things like pin squats in that weak range of motion, but I also understand flexibility is appreciated.


I think people expect thorough outputs of data that aren’t realistic from VBT devices. A simple example is velocity-time graphs, acceleration-time graphs, displacement-time graphs, and displacementx-diplacementy graphs. Firstly, much of that information can be obtained in more qualitative ways and perhaps in more appropriate ways through video. If you want it in more quantitative ways (because you absolutely need to know what the bar displacement/speed is every 60th of a second, etc), you can run it through some free video analysis software. I prefer to make more qualitative judgments through recording sets where appropriate (external, subjective – if you didn’t skim through to this point), but it might be helpful to get down to the nitty-gritty for top-end sets or near competition prep. Some VBT devices might offer this and others might be developing it for future updates, but don’t expect it right off the bat or think that’s the only utility for VBT. You could get that sort of overly-analytical information for free with equipment you have now, but it’s not going to be immediately actionable (nor does it need to be).

               Some might be lost on what I’m talking about. Here’s what displacement-time, velocity-time, and acceleration-time graphs would look like.

Displacement, velocity, and acceleration in the y component vs time. Data pulled from tracker.
All X axes are the time in seconds. The Y axes from top to bottom are displacement, velocity, and acceleration. All graphs are synced to time. These might be useful to have, but you’d have to have a decent intuition and understanding of what these sorts of graphs are supposed to look like for different movements. If you wanted to track bar path in the X and Y (fore/aft and up/down) quantitatively across time, you could do that if you had a triaxial graph, but it’s more helpful to watch the graph as the video plays. Here’s an idea of how messy that information can be:
An example of an ugly and indiscernible x-y displacement graph. Scale is important here. Notice the X axis is emphasized

               It’s probably going to be more helpful to watch the graph as it plots. This video (linked to watch in a new window) explains exactly what I mean. All this information was obtained through an iPhone shot at 60 frames per second and a free software called Tracker

Open Barbell Output
as of Feb 2017
This means this is very low cost. Maybe spring for a tripod with a level on it and a phone holder. Bryce Lewis from The Strength Athlete has a YouTube walkthrough of how he uses it, but it’s very, very intuitive for an entry level user given a remedial understanding of physics. VBT devices not having this may be a limitation, but it might not be worth consideration when purchasing a device. Getting a VBT device for this exact purpose is like buying a BMW because you like the cup holder. I understand holding beverages is important, but the main purpose of BMW’s is not their cup holding capacity. Consider how “little” information Open Barbell as of February 2017 presents. The data is not super sexy, but it has a high level of utility. I know VBT isn’t necessarily in the habit of presenting itself as KISS, but maybe we should just keep it simple, stupid. With the output in the picture, you can get 85% of the data you need to make actionable VBT decisions.


Some systems give you measurements of force. Some don’t give it to you upfront, and you’ll have to export the data through a web portal that syncs all the metrics. How it determines force is somewhat amiss to me, but the easiest way would be accepting the user input of mass and multiply it by acceleration since F=ma. This isn’t “real” force though, it’s just force of the barbell that's mostly in the vertical direction, a rough proxy for ground reaction force that accounts for the lifter’s body mass and all resultant forces. It's sort of a truncated metric of force, viewing the system as the barbell and additional weight alone. Nonetheless, sometimes a proxy is good enough. At least I think. Who knows, it's proprietary. 

In the Westside Barbell scheme of things, you can train force output (and therefore strength) by increasing mass on the bar, or increasing acceleration (reminder: F=ma). If you work with a system that actually outputs force, you’ll see that you mostly increase Force by increasing mass and the discrepancy between light and fast weight force vs heavy and slow weight force tends to favor heavier loads. Conceptually it sounds good, but in practice it doesn’t work out so well if we accept force as measured by VBT devices. Mike Tuscherer has written about it on JTS (here and here). Jovanovic also makes a strong point that viewing it from the exact readouts of force output might not be the most appropriate way of looking at speed work. Chad Wesley Smith has more thoughts on the matter in YouTube format if you're extra lazy. The TL;DR version is you produce more force by just adding weight while moving as fast as possible - not by using lighter weight and trying to move it faster. At that same time, it's arguably whether the long term outcomes of training at submaximal weight as fast as possible is comparatively better than just training with heavyish weight. There’s a host of other reasons that people inside and outside of the PL world have cited why this sells well but delivers short, but I won’t belabor the point. You might want to have force as a metric, but you don’t really need it. Weight on the bar or velocity is a good enough proxy.
Force and Velocity by %1RM on a straight bar
deadlift and a hex bar deadlift. Source

If you are focusing on the power output (or force even) and other metrics that calculate based on load, it’s probably not appropriate to take some of that information seriously when it comes to accommodating/variable resistance. That would include bands and chains. It will record velocity fine, but power accounts for mass as well. Usually, it’s measuring power as the product of force and velocity. Since force is the product of mass and acceleration and it has no way to track the change in resistance from the top of the lift to the bottom, that measurement is close to meaningless. VBT isn't the best way to track this change in resistance. You might be able to use velocity to autoregulate the training, but it might be more appropriate to use another method like RPE. I guess you could also do a 3D video analysis, manually calculate to include elasticity of the band, and make your workout as math heavy as launching satellites into space. Maybe as long as variable resistance is a tightly fixed percentage of bar weight this might make sense. Maybe keep it simple, stupid?
If we're going to use biomechanics to drive the training process, it's best if we have something that does the thinking for us. I don't advise mixing physics and exertion.

In any case, I think it's disingenuous to transliterate velocity to training quality in all respects. It sounds good on paper if you accept the table of training quality and movement velocity as dogma. But I would venture to say using variable resistance and inertial considerations is better at training a weakness in a range of motion (EX: speed out of the hole) rather than some classical Russian classification of strengths. I like my Russian ideologues, but I disagree with citing them dogmatically. The right answer probably starts with, "Well, it depends on..." Many of the folks espousing these ideas insist you need a good grasp of physics to think about powerlifting. Probably. But physics brings up many counter-arguments to speed work. Short of calling speed-work bullshit, it's an unanswered question.
Furthermore, VBT for power works well as a guage on force in movements where you don't leave the ground. If you leave the ground, like a squat jump, you're no longer exerting force on the ground. Think of jumping up and down on a bathroom scale. When you do the counter-movement and load the legs, the scale will read higher for a split second. When you've actually jumped, the scale will quickly return to zero. If you did this with a bar on your back, velocity would still be reading over the whole length of your jump. So if you're 1.67 meters tall, jump 0.3 meters for a quater of a second, it has averaged in 0.5 seconds of flight time where there is no force being exerted on the ground. There are other ways to use VBT here, but it's best not to take the readout at face value. This is also why Bryan Mann likely uses peak velocity for cleans.


Exercises that have a balance component might not be appropriate either. Adding the extraneous detail of maintaining balance skews things in terms of velocity. While it might be hard on a motor pattern level, the muscle might already be strong enough to gauge its objective feedback without VBT. This applies equally to those pistol squats as it does to those SSB Squats you added into your routine that you’ve only started doing. Usually, you want movements you’re proficient in, and that’s more of a judgment call. It’s for this same reason that VBT's not appropriate for beginners. There needs to be a certain amount of confidence with the movement before the metrics become meaningful.

If I had to guess why movements that have a high balance component don't fit it, I would guess it's because the constant movement in multiple planes skews the vertical velocity. That movement in other planes usually isn't part of consideration for vertical velocity. In theory, this might be more pronounced with systems that measure movement in less planes. Accelerometer systems, for example, usually measure in 3 planes. Tethered systems usually measure in one plane (Tendo, T Force, Open Barbell), but GymAware measures in two. Bryan Mann has said in the past he also has issues with front squat velocity, and I think it could be related to this. Bryan Mann also uses the Gym Aware.

One way to remediate this situation is to decrease the balance required. Squats with a safety squat bar (especially ones with a radically forward camber) are a great example of this. The movement generally is heralded because it pulls you out of position on purpose, forcing you to have greater stability. IF you wanted to smooth out velocity across a set (make it so you have a solid read on successive velocity decrements each rep), you can separate the eccentric and concentric portion. So instead of doing regular SSB Squats, do SSB Squats from pins. Lower the bar to some safety pins/straps, pause, then lift the load. This does change the training stimulus though. The training stimulus is even less so if you modify it further. For example, if you wanted to make sure the camber was challenging you in the bottom position of the squat, you could lower to just above the safeties (not touching them), hold for whatever amount of time, lower the last inch down to pins, then lift the load. I've done this successfully with my SSB Squats from pins, but then you have to live with the fact that you're maring such a beautiful bar.

This is a point of contention emerging in the VBT circle. Banyard et al recently put forth that velocity is less stable in free weight exercises because of the stretch-shortening cycle (SSC). Their main contention is that most experiments have been conducted on a smith machine (which provides some study constraints that help elucidate factors but also loses some context). Their case sort of sits upon the idea that the SSC is mitigated by the smith machine. I will say that's a pretty fair point. You can demonstrate it easily by performing a free weight bench press followed by a pin press. A pin press will generally create a higher R^2 for its load-velocity relationship. By contrast, though, the popularity of dive-bombing your squats on the platform to overcome your sticking point in powerlifting isn't nearly as common as it is in something like weightlifting or general strength and conditioning. Long story short: don't bounce out of the hole or off the chest. 

You could apply this same concept to other variations that have a balance component. Reverse Grip bench press is a possible example (I've never done it, but worth checking out). Front squat might be a bad candidate for this though. If you were to front squat to pins, lowering the bar onto the pins could only amplify the balance requirements by pulling the bar out of the front rack position. There is a possibility you can negate that with a cross-armed position or straps around the bar, but I also haven't tried this. I've heard from some other lifters that lessening the shoulder/torso balance component of the front squat (front squatting with straps) mitigates the noise of successive velocities.


VBT can be a useful way to auto-regulate training. If you find that more frequent feedback helps enhance your training or that external, objective feedback really helps, then VBT could be a good fit. If you prefer dedicating yourself to a set plan and can’t be sure to trust the information external, objective feedback, it probably won’t help you. To some extent, implementing VBT can mean diverting from fixed planned training and individualizing your training practices, but the extent to which it does that depends on how you implement it. There’s no guarantee that you’ll make gains by injecting VBT into your program alone. Ask your doctor if VBT is right for you.

VBT has the potential to give you quantitative ways to understand the appropriate intensity, fatigue, exertion, and technical proficiency. They aren’t the only way, but the feedback can be succinct and actionable. It is meant to be a training tool, not a training necessity and any attempt to make them essential to that process is likely to be met with limitations. These limitations can include limiting how tempo reps are used, VBT regulation of a general physical preparation component, VBT regulation of isolation movements, and balance predominant movements. Additionally, it’s important you establish an understanding of what metrics you need it to collect as features are not universal across all VBT devices.

At the end of the day, VBT is a training tool for the tool box. If VBT is the most insightful part of your program, your program is probably lacking. I would argue that how you distribute your training load and your exercise selection will have a greater impact than just adding a VBT element. Despite how much I'm also laying out the case for process-oriented training, I'm also arguing the importance of planned training. If you don't have experience with percent based training, you'll probably struggle to find the appropriate way to implement VBT. I would advocate the appropriate transition to VBT is to take an existing percent based training program (or design one), and then add elements of VBT as you go. Where VBT doesn't fit, use traditional progressions and loading schemes, or attempt to blend other autoregulation methods like AMRAPs and RPE.

Plenty of people have been breaking records and getting strong without VBT. As interesting as VBT might be, there's not an extensive roster of people that are dominating national or international powerlifting meets and espousing VBT as the reason. My qualifications as a powerlifter are questionable as well, even when you narrow the consideration down to my weight class. My position as an "expert" in VBT for powerlifting is not backed by my achievements. If you asked me, I don't think you're training wrong if you aren't using VBT. My purpose here is to give an accessible understanding of how VBT can be used in powerlifting, and also just refer people to links because it's not something that can be explained easily in conversation.

While this article mostly concerned reasons to implement VBT, the next one will build on that giving the nuts and bolts of what makes the whole system work. Eventually, this will get to a point where I'm giving example programs I've run to achieve different training goals. The current plan is to release everything in 1-week intervals, and this series will come to an end at some point.

Monday, February 13, 2017

A Powerlifter’s Guide to Velocity Based Training Pt 1: Device Comparisons


-The purpose of this article is to address the validty and reliability of velocity based training (VBT) measurement devices. 
-Three devices were compared to video analysis: Beast, PUSH, and OpenBarbell V2. Of the three, OpenBarbell seems the most appropriate for powerlifting. 
- “This will be covered largely from a powerlifting standpoint. Also, did I mention this is geared towards powerlifters? I mostly wrote this for people interested in improving their squat, bench press, and deadlift. Athletes that focus on these movements in particular are powerlifters. I wrote this for powerlifters. Powerlifting.” 
-The most important considerations for a VBT device for powerlifters are affordability, reliability at low-end velocity, and support for powerlifting specific movements (primary and secondary lifts) 
-There is nothing that makes a tethered or accelerometer VBT device better than other options without testing across different movements you intend to perform under VBT conditions 
-The limitation of an analysis like this is accuracy or reliability can be improved in some models with no additional hardware changes (adding something to the internals). An update to their respective apps could change how velocity is calculated, rendering this analysis null and void. This was conducted in late January of 2017
[Update 2/18/2017: Added conventional deadlifts. Unfortunately, this addition only includes PUSH and Open Barbell because I no longer have the Beast sensor.]
[Update 8/17/2017: Added some additional commentary. Since this has been released, I've gotten feedback from some manufacturers. As before, this is a snapshot of device performance in early 2017.] 


Velocity Based Training (VBT) is one method of auto-regulating training. It can auto-regulate load on the bar, number of reps within a set, total number of sets, any combination of those three, or any other relevant factor in training. It is beyond the scope of this article to make the case for VBT. It’s hard to make a case for VBT when you haven’t first established that the methods used to gauge velocity are valid and/or accurate. VBT has been a training methodology put forth in power athletes and team sports. It has gotten significantly less attention for strength athletes like powerlifting. Other coaches can more appropriately talk on the matter for strength and conditioning outside of powerlifting, and people like Bryan Mann, Carl Valle, Dan Baker, Eamonn Flannigan, and Mladen Jovanovic already have. On the powerlifting side of the house, the volume of writing and academic work is limited to Louis Simmons of Westside Barbell, Brandon Senn of Kabuki Strength, Mladen Jovanovic of Complementary Training, and I guess you could also argue that Mike Tuscherer of Reactive Training Systems as well – although it’s more appropriate to say Mike uses velocity as a reference point, not a driver of training.

The case for VBT in powerlifting is much the same case as it is for auto-regulated training in powerlifting. Rather than make this tangent over-shadow the assessment of validity and reliability of the sensors, I will direct you to Brandon Senn’s article on the auto-regulation book of methods or wait until I’m able to produce an article that addresses this specifically.

Powerlifting is not a money sport. If you want the best system with the best reliability and accuracy, you should probably do what universities do to test the validity and reliability of velocity based training (VBT) devices. They commonly use VICON 3D analysis systems, or even just run a cross-comparison to another system that has an established track record and vintage prices. Other systems that fit this condition include the T-Force and Tendo linear position transducer. All of these systems are priced out pretty high, so what we’re left with are consumer-grade options, which could arguably be good enough.
Some folks have talked about how linear position transducers, devices that measure displacement and velocity by attaching a lanyard to a barbell is the "gold standard" for velocity based training. There is no gold standard. Saint Verkoshansky, patron saint of the force-velocity curve, did not part the heavens and annoint a clear winner, so let's put that dog to rest already.
Keep in mind, not every device is marketed with the powerlifter in mind. In general, many of the options are aimed at strength and conditioning coaches for power athletes and sports, not for the exclusive use of strength or hypertrophy development. If you just want something to collect silos of data with no contribution to your training plan, there are no particular suggestions for you. If you mean to use it for strength and conditioning, there are many factors to consider – none of which I will cover. Other more qualified evaluators like Carl Valle have covered this in better depth than I could or care too (no offense, I’ll keep following you on Twitter Carl). Powerlifting is the odd-man out here. There is little regard, little attention, and little support in the hardware or software to enable VBT for powerlifting.

Cost is probably the first thing to think about. Unless you’re a sponsored athlete, you’re probably going to consider the more affordable options. Once you’ve determined your budget, it’s essential to consider the coverage of exercises you intend to use it for. This is particularly important because some exercises bottom out at lower velocities than others. It’s also important to consider the direction of the manufacturer. If the manufacturer caters mostly to recreational weight lifters, it probably won’t be that appropriate for you. On the other hand, if it caters to another barbell sport like weightlifters, it might be appropriate for you. And lastly, if it caters to power athletes in team sports, its function and implementation for powerlifting is probably outside of your scope of concern, but might dual purpose well enough. One easy way to see the direction of the company is to look at its change log on its accompanying application. If many of the changes pertain to increasing exercise variety and features that pertain to powerlifting, it might be headed in a direction that will be suitable down the road if it isn’t already appropriate at start up.

And lastly, anyone that says that people should just use BarSense or IronPath: I challenge you to run a 6 week cycle of VBT strength training at intensities of 85-95% with at least 33% of all repetitions performed using VBT feedback. It won’t work, even if the applications work as advertised. The fact that there isn’t an app in the Google Play or Apple app store that utilizes phone internal sensors is beyond my understanding, but no such feasible, low-cost/no-cost option currently exists that operates in real time. And it’s not because VBT is new, because tethered units that have filled a VBT capability like the Tendo have been available for a long time. Anyone recommending this option might as well be recommending a recumbent bike to drive the training of a weightlifter. This is an ignorant argument that doesn’t deserve more than a paragraph of concern.


This whole section is worth skipping, but here it is… Here’s an obligatory, not-all-inclusive table, because people like tables.

Bar Sensei
Not Listed
Method of Measurement
Tether displacement w/o angle of pull
Tether w/ angle of pull
Accelerometer and barometer, attaches via bar collar
Accelerometer, attaches to the bar
Accelerometer on a barbell or strap
Accelerometer and Gyroscope, attaches to the forearm
Tether w/o angle of pull
Cloud Syncing
Data Export
Software supported
Time to Feedback
If not real time, after set
Apparent Purpose
Academic and weightlifting
Anything involving a barbell
Recreational lifters
Power athletes
Recreational lifters
Power athletes and recreational lifters
Anything involving a barbell

So if anyone asks, “Bruh, Y NO GYMAWARE?” look at the price. This blog is NOT monetized and is strictly here for dissemination of VBT ideas in powerlifting. But if someone wants to loan me one, I'll definately add it to the comparisons.

A scatter plot correlation of video velocity and a velocity
measurement device


First let me explain Bland-Altman plots via scatter-plots.

The X axis is velocity (everything in meters per second) as measured by a Beast sensor. The Y axis is velocity determined using video shot at 60 fps and a free application called Tracker. I’m shilling for Big Physics. You could also use Kinovea, but for the volume of work I was doing alone and the quality of computers I have to work with, this was easier. The dotted line represents how the measurements are correlated to one another. A cursory check of Tracker’s determination of displacement and time appeared to line up with what I could confirm in more rudimentary ways. Many things could affect this as a standard of comparison and it may have been more appropriate to exclude using the program, such as taking the average of all sensors values as the dependent variable. For reasons that I cover later, this was not the most optimal designation of variables.

An example of what a Bland-Altman plot tries to do.... sort of
About the graph: the further from the line, the more they disagree. If the dot is north of the Mason-Dixon line, the video analysis measured the movement at a faster velocity than the Beast sensor did (or that sensor measured it slower than the video). If it’s south of there, then the sensor measured it slower than the video (or vice versa). The slope of the line shows the bias across different quantities. Potential scenarios are that the device could be more accurate as slow velocities and less at fast velocities. In a perfect world, if the graph was scaled at 1:1 (length of grid line matched the height of gridline for the same number of units), this line would form a 45-degree angle. The problem with a scatter plot is putting too many comparisons on it would look too busy, especially in our case if we were measuring different squat type movements (this is measuring back squats, front squats, and pause squats) across three different devices. A Bland-Altman plot helps us visualize it in a greater context by essentially rotating the graph 45 degrees and giving new horizontal and vertical axes showing video analysis velocity and the difference of the sensors relative to the video’s measurement. Something like the picture on the right.

So what does that look like in practice? Like this for a squat: 

Firstly, notice that the horizontal axis (video analysis velocity in the Y direction) is reverse ordered, showing the fastest squats on the left and the slowest on the right (because that reflects intensity/exertion from low intensity/exertion to high intensity/exertion). The vertical axis shows the difference relative to the video, with no difference lying in the center at 0.00 m/s. The colors show different sensors used, and the shapes of each point denote the type of squat. The legend helps you out here: back squat, front squat, and pause squat.

It’s important to note that the squat is likely going to be your longest movement in terms of distance. Since velocity is displacement over time, that means velocity is attenuated by that. For most people, squats will be faster than bench or deadlift. As we decrease velocity (move to the right on the graph), we approach heavier loads. You’ve probably noticed in your own training that you aren’t able to lift your 1 rep max (1RM) as fast as your warm up weight. Velocity reflects this.

You can generally see that OpenBarbell clusters in a generally straight line. At higher velocities, PUSH holds its ground, but it does have a little bit of scatter gun spread going on further down the low end – the part that’s most pertinent to powerlifting.  Beast is roughly near that. But more importantly, this is a comparison of a tethered system against two different accelerometer systems. The supposed superiority of tethered systems is they are more accurate (closer to zero difference). This doesn’t show that. But it does show that it’s reliable.

Accuracy isn’t too important for VBT, but reliability is. Accuracy would reflect how “true” the measurement is to what it’s measuring. So if the 2x6 board is 30 inches, it’s more accurate if it measures it at 32 inches than it would if it measured it at 48 inches. Reliability would be measuring the board 5 times with two different tape measures. One could give a reliable measurement (42, 41, 43, 42, 42) and another could give an unreliable measurement (30, 49, 15, 26, 52). Ideally you want both, but for VBT training purposes reliability is all that’s important. Bad carpenters blame their tools, really bad ones buy twice as much wood. 

Back to the reliability though: if you notice, the differences between sensors and video seem to shrink at slower velocities, or get closer to the 0 m/s difference on the Y axis. Slower reps of the same distance take more time. If you’re dividing the same distance (assuming all your squats are generally the same length of displacement) by increasing times to complete the upward portion of the lift, it slows down and the potential for inaccuracy decreases. Put another way, if it’s reliability is something like plus or minus 5%, smaller quantities (velocity) tend to have smaller difference. But that small difference could be huge. For example, a squat at 0.34 m/s could be tolerable, but a squat at 0.28 m/s could be slower than an individual is able to grind out – like a load above your 1RM that somehow dogmatically followed the trend line and ignored force capacity. It’s probably not helpful to think of VBT as an overly precise tool in prescribing load according to velocity though. Usually, when prescribing a velocity to train at, it’s better to aim for that velocity but accept a range of velocities above and below it. Not huge margins, but if you're aiming for 0.44 m/s, 0.41 or 0.47 m/s might be acceptable. I've seen some templates that seem to use around 5% variance from the target velocity.

The shapes also help us identify if there are movements that are particularly tricky for different systems to measure. In this case, PUSH does not measure front squats as reliably as back squats or pause squats (which is a back squat variant). I’ve always suspected this after loading the bar according to the load-velocity relationship at what should be 70% 1RM and finding myself only able to crank out 5 reps.

If you want to be super technical, here’s the individual points by video velocity and difference for Beast, PUSH, and OpenBarbell. Here’s the correlation between video velocity and Beast, PUSH, and OpenBarbell. If you’re happy with just the coefficients of determination for Beast, Push, and OpenBarbell, they are 0.93, 0.84, and 0.92.

”The coefficient of determination, denoted R2 or r2 and pronounced "R squared", is a number that indicates the proportion of the variance in the dependent variable that is predictable from the independent variable(s).” The range of coefficients of determination are 0 to 1, with closer to 1 indicating that the regression line perfectly fits the data. 

This does not give the full picture though. To date, I have had zero “dropped reps,” or reps that weren’t detected by OpenBarbell. OpenBarbell gives me so many fewer dropper reps compared to other devices and it's fairly immediate to check before you start whether it's actively recording data. Dropped reps in VBT is what lag is to computer gaming: it’ll kill you ded. The squat is generally more reliable as an exercise because it’s faster and manufacturers know that if you can’t get squats right you’re considered useless because DO SQUATS! PUSH didn’t detect one rep of front squat, as did Beast. Beast also dropped one regular squat. This might not be a big deal on the surface, but if you were trying to determine velocity at 100% 1RM (which you could figure out through AMRAP, arguably) and your sensor dropped one of your 8 reps, that velocity could be lost to the gains goblins of the labyrinth. The opposite could happen too. The sensor could detect 14 reps when you only did 8. Beast calls these “ghost reps” and gives you the ability to choose the ones to cull – which are sometimes obviously wrong and sometimes arguably could be a real measurement. PUSH, on the other hand, only lets you tell it how many reps you did (if you kept count), and determines which measurements to cull without further input (part of their rep detection algorithm).

Again, these methods are as of January, 2017. Manufacturers are always updating their apps. Take much of what I say here as a "snapshot in time" and if you have further questions it's better you check the app reviews or contact me directly. If you think I'm going to review and edit this blog every month, you have a cute relationship with reality.

Sometimes it’s more helpful to manipulate the system and say you completed one or two more reps than you actually performed just so you can see the full range of measurements, but this can get screwy. You could potentially make the system give readouts for reps you didn’t complete. In the case of these charts, dropped reps have been removed from the data set and it biases the measurement to some degree. Keep that in mind throughout this. Reps that these units didn’t detect could possibly be excluded because they are markedly different from adjacent reps and the system self-identifies its own measurement variability. This is the technological equivalent of your dog running into the other room as soon as you come through the front door because they broke the lamp again.
What do I mean by removing dropped reps? How can I remove reps that don’t exist? For example: imagine three dropped reps that were measured by video at 0.3 m/s. If the reps were dropped, that essentially means the difference is -0.3 m/s. If it was a fast rep (which is less meaningful in powerlifting, but here’s an explanation regardless), a dropped rep can mean a difference of -0.75 m/s. This difference is huge. The effect of including them is it misrepresents the bias trend for the rest of the recorded reps, which is of greater interest in the presentation of the data. The unfortunate downside of this is I have to make well-reasoned assumptions as to what are dropped reps vs what are ghost reps.


These measurements do reflect one of my programs, which will be released later. As a result of that exercise selection, there are more data points for bench than there are for the other movements. This is an obvious excuse for why I’m shilling for Big Italy (such innuendo). Exit grapherrhea:

Again, Open Barbell performs fairly reliably and arguably more accurately and reliably. The region of most importance, at 0.60 m/s and below is very tight. Beast seems to handle pin presses very well, which is surprising because Beast usually gets confused when you change direction rapidly (like a barbell bouncing oh-so-softly on safety pins). It almost appears like PUSH has a sinusoidal shaped bias, but it’s hard to tell. This could be a result of how the data is smoothed from its sample rate down to a usable signal. Even though Beast performs better at lower velocity, generally, it also has some scatter at mid-range.

When I say "mid-range," I actually only mean in terms of this graph. In terms of bench, I hardly ever use faster than 0.5 m/s for working weight. This gives a broad picture, but again for powerlifting you should probably focus on the slower stuff. Generally speaking, a powerlifter should have faster reps in higher rep/lower intensity work. A good rule of thumb is to pay special attention to velocities less than 0.6 m/s in the squat, 0.5 m/s in the bench, and 0.4 m/s in the deadlift. If you pull sumo, maybe even slower than that, only paying attention to 0.3 m/s. That's my experience though, YMMV.

Bench press variants surprised me. In a previous article in a blog, I tested multiple PUSH bands at the same time. I tried to set up conditions that tested its reliability, with some possible failure points and some protocols I chose specifically because I was sure they would fail (by using the device incorrectly). At the time, the main validation article PUSH had under its belt utilized curls and multiple individuals at East Tennessee State University under Sato, Beckham, Haff, and Carroll (full author list because Carroll has written more on VBT since then). So I replicated it, broadening the conditions. My “obvious fail” condition was wearing the device in it’s normal configuration on the forearm and comparing that to wearing the device incorrectly at the wrist. The results were fairly consistent. It became obvious that it was measuring angular acceleration and from there determining angular velocity. In the account creation process, one of the inputs you have to give is your weight and height. This was supposed to be a failing condition of my test, but instead I figured (not me actually, my boss did) that it was likely referencing distance and position of the sensor relative in space given proportions of extremities of your height. Further explanation is beyond the scope of the article, but here’s two links to get you started.

My assumption had been that because PUSH likely used angular acceleration, it likely performs better than it should in comparison to other devices in movements that were attenuated by forward/backward movement combined with upward/downward movement. The bar path on the bench press is different from the squat and deadlift in that respect. Greg Nuckols covers that in detail here as does MySquatMechanics, which is my cop out to abandon that tangent. Long story short, I expect PUSH to be better at this than OpenBarbell or Beast. I expected this even more so with reverse grip (RG) bench press since the movement arcs down farther towards the upper stomach or bottom of the sternum. At the low-end of velocity, it tends to do that for RG bench, but it appears scattered in a sinusoidal pattern throughout. Beast performs at a generally predictable bias, but is also scattered at higher velocities. Open Barbell continues to perform well, especially at lower velocities where powerlifters will do much of their important work. Its data generally speaks for itself.

For point of reference, I usually grind out my slowest rep (1RM, no coincidence) at 0.10 m/s. In other studies, 1RM for bench is typically around 0.15 m/s (link to a review article). For powerlifters, Helms and Zordous have found it to be even slower (0.11 IIRC). Most accelerometers systems tend to perform less reliably (anecdotal evidence mostly, but also some implication by manufacturers) at velocities slower than 0.15-0.40 m/s, or in my case ~80% 1RM and above for a bench press. Again, with squats this isn’t nearly as clutch, because 1RM’s are usually around 0.30 m/s (0.24 m/s for powerlifters, again by Zordous and Helms - I think), so we’re not as close to the edge of the variability cliff. Many individual factors will influence your velocity, such as shortening the range of motion because you take a different stance or grip, or you’re American by birth but of Asian height by the grace of God (I can say that, I’m Filipino). For reference to my 1RM velocities (MVT – minimum velocity threshold), I squat at hip width, bench wide, and have a sumo deadlift at 5’5”. My individual experience, thusly, is very challenging for systems that can’t perform as well under 0.40 m/s.

No one wants to tell their best friend they have an ugly baby, but they should hear it from someone that loves them first: PUSH had 4 dropped reps, Beast had 3 dropped reps. As before, OpenBarbell does not drop reps in my experience of over 500 to date drops reps less often and easier to check if it's holding signal before you lift. As before, excluding this data means Beast and PUSH appear more accurate and reliable than they truly are.

Coefficients of determination: Beast=0.81, PUSH=0.92, and OpenBarbell=0.98.


Deadlifts are usually the least forgiving in terms of accelerometer systems dropping reps. I would love to prove that, but I only deadlift twice a week and I only have 48 reps to populate data for PUSH and 35 for Beast. PUSH is notoriously bad at this, and it dropped 7 reps (14.5%). In my n=1 experience, Beast also drops lifts, but that is not substantiated in the current data. I can also tell you that because Beast over-records all movement, you will get significantly more ghost reps in a deadlift if you aren’t setting the bar down quiet enough for planet fitness to approve. This also introduces some bias into the measurement, because even though I’m fairly sure most the measurements included were actually detected and weren’t ghost reps, I’m not absolutely sure. Ghost reps are a huge deal if they register at ~0.30 m/s (which they mostly are) and your deadlifts at 75-80% 1RM only move that fast or slower.

Nonetheless, you’ll see slightly more variation in Beast and PUSH than you will OpenBarbell. Most importantly, you’ll also see this most pronounced at lower velocities. The range of difference nearly doubles. I believe it’s more helpful to see all the individual comparisons separately on the same scale, which I have compiled here.
Given that some accelerometers are measuring angular acceleration, calculating angular velocity, and churning that out into vertical velocity, you could see that something like a deadlift could be challenging. If the unit detects best by change in angle of the unit and the arm is fixed in a downward position throughout the movement, then it doesn't have much to detect. 
This data is very biased by design, but not purposely so. My deadlifts are slow and sumo is usually slower than conventional. As before, less ROM=less velocity. Additionally, I believe the reason PUSH drops reps so often for deadlifts could be is because the sumo deadlift algorithm is fairly new – at least I think they use a different proprietary algorithm for sumo than they do conventional. Since I updated the chart, I think that is the case as 13 of 14 reps of conventional deadlifts recorded. The sumo deadlift algorithm is a year old whereas conventional has been a part of the system since release. Upon early release, the “fix” for rep detection on the deadlift was to complete the pull, drop the weight from hip height, and complete additional reps in the same manner. I think they have since changed this, but there is a possibility that this could also “fix” the sumo deadlift problem. If you’re addicted to data, I guess you should try that out. If you’re just trying to git sum dedlifts, then it might behoove you to find another way to auto-regulate deadlifts.

In general, deadlifts are perplexing for VBT, and I have no definite reason why. Everyone I’ve talked to from Mladen Jovanovic, to Brandon Senn, and other normal VBT device users of Reddit tend to agree with this. 
If you’re really interested in VBT for powerlifting, Mladen Jovanovic and Branden Senn are the best place to start. Bryan Mann, Dan Baker, and others that focus on VBT don’t tend to touch on topics of absolute overlap with powerlifting (bench throws, prone rows, and cleans don't have correlate perfectly to powerlfiting performance), but Mladen and Brandon do cover topics of direct translation to the sport. No offense to Mann or Baker, their insight and lectures have been a great help. 
For many exercises, the first rep of the set is the fastest, and following reps have successive speed decrements if the reps are performed with consistent form and maximum volitional velocity. The widow maker doesn’t do this. Trying to game the movement through starting the movement on the rack at knee height, touch and go reps, pull and reset to the floor reps, performing cluster sets, or pausing at different positions during the lift don’t seem to smooth out the movement’s behavior. This is the ugly baby that VBT proponents don’t like talking about, and opens the floor to many ways of trying to understand how to use the feedback VBT devices provide. It is entirely possible that VBT isn’t appropriate for deadlift autoregulation, or we just haven't figured it out yet. Basing our assessments of performance on subjective measures might be better suited (like RPE) unless we’re talking about final reps left in the tank. This subject deserves an article unto itself.

This phenomenon is reflected in the correlations between video velocity and sensors. Beast has a coefficient of determination of 0.64, PUSH at 0.59, and OpenBarbell at 0.80. Given how well each system generally performed in previous lift classifications, these numbers pale in comparison. Keep in mind, these R2’s are based on the whole range of differences from 40% to 85% 1RM. If you were to increase the sample in velocity ranges typical for powerlifting, there might be completely different conclusions. I decided to include conventional deadlifts after initially publishing this to the interwebs, and I think the differences were only of consequence to PUSH. Unlike PUSH, Beast uses a generalized algorithm for most movement types. Because PUSH dropped so many reps, there was less of a sample size to work with. Knowing that conventional was a long standing detected exercise, I decided to include for clarity's sake, although I realize this comes at a potential loss of comparison to the Beast sensor - again, maybe not since the algorithm is generalized on their data processing. The Beast sensor was not included for conventional deadlifts because by the time I decided to do this I had returned the sensor to the owner.


The point of this article was to cover the validity and reliability of different VBT devices. Some of these have had their own validation studies and others have studies in the works, but I hope this rudimentary analysis gives you an idea of realistic expectations. It may sound like I’ve been harsh to accelerometer systems, but I would like to bring to your attention that the orientation of this is for powerlifting. Some of these devices weren’t designed to operate within the parameters of powerlifting optimally but do excel in other areas that I have purposely excluded. Tethered units, to include GymAware, aren't super appropriate for 3 axis movement like a bus driver, swings, etc. They're also not super great for movements in which it's not a barbell being manipulated but the body, dumbells, etc. Accelerometer systems tend to circumvent this issue. This evaluation is not meant to be fair, it is meant to gauge narrow, appropriate implementation of VBT devices in powerlifting.

Of the three options, OpenBarbell does appear to be the best suited for powerlifting movements, however it’s application to deadlifts is more limited than it is for benching and squatting. On the surface, it might seem that it may only be appropriate for 66% of powerlifting exercises, but given that many use squats and their variations to build their deadlift I would argue it still has relevance. I would also argue again that this evaluation is a snapshot in time of late January in 2017 and does not speak for how future updates to the hardware or software will augment validity, reliability, or utility of the different VBT devices.

Here’s a table:

If you wish to see more comparisons added to this, I’m willing to evaluate other models as long as it doesn’t involve obligating me to purchase them. In particular, I would like to see Gym Aware added for comparison. I would not like to see the Form Lifting collar added yet as it is a new product and would be unfavorably skewed against an emerging technology which could arguably have valuable technological contribution to VBT. The manufacturer seems to agree with me on the matter in our exchange via email.

It’s worthwhile to point out the limitations of this analysis. Firstly, I’m using questionable video analysis software as the method of comparison across all exercises. On the surface, it does not seem to be a huge concern because the main anomaly in the measurements appears to be deadlifts, but given that other professionals seem to acknowledge the unique nature of deadlifts maybe that is real. However, it does seem odd to me that there are measurements near 1.35 m/s. I have never seen any device measure this high. That velocity is comparable to the peak velocity of weightlifting movements, and I will agree it is suspect. If I had to guess, Tracker is likely overestimating velocity, but given that all movements are from a side profile the bias is likely proportional. This is reflected through the straight trendlines. I’ll cover how I have used Tracker in a following article or video. It would seem to me that it is over-estimating velocity at least at the high end. This discrepancy appears to behave uniformly though, so it may be suitable to use it as a comparison. I could also reanalyze the data to use methods of comparison when there is no known validity, such as comparing the difference of one measurement to the average of all measurements of that given repetition. There are also inherent flaws in that method, especially when you factor in dropped reps. This method could unjustly punish devices that do detect repetitions, which is bass ackwards. Furthermore, this method only works when there are simultaneous measures of the same movement - like a rep being measured by all devices at the same time. The current methods allow for future movements to be added to the comparison graphs subsequent to January, 2017.

Another way to plot the difference would be percent of the difference from the comparison, or the percent difference in the velocity measured by video and the sensor. This could flatten the trendlines, possibly revealing the percentage of velocity is over/underestimates. 

It’s also suitable to consider that one subject isn’t appropriate to generate the data points and a sample of multiple individuals might smooth out variances within a group due to differences in movement proficiency (or lack thereof), limb lengths relative to height, and a host of other factors. I hope the slack that I leave will be picked up by people that are currently evaluating these technologies with funding in universities, such as Dr. Zordous from Florida Atlantic University.

In terms of how to implement a reliable device into a powerlifting program and how to utilize feedback from VBT devices, I will cover these topics in other articles. As a first article, it doesn’t make sense to imply the efficacy of this technology in the sport without first establishing it’s validity and reliability. 


I tried to standardize the range of the scale here to improve the clarity of things.