What Does Velocity Within A Set Indicate About Training - By Kevin Carroll



Velocity-Based Training (VBT) conceptually seems to be very simple: the use of velocity measurements to gain daily feedback on training. However, are we OVER-simplifying the use of velocity for monitoring and coaching purposes? A look into the existing literature on VBT might indicate that things are pretty cut-and-dry in that its uses are generally accepted and agreed upon. Is it possible that we are only scratching the surface here? Is it possible that we’re only looking at one side of the coin?

It is my belief that we need to do two things here: 1) Challenge everything we currently know about VBT in order to either confirm or revise the ‘rules’ that have been established; and 2) Ask questions that we have not answered yet. Recent research from Zourdos et al. (2016) suggests that a lifter’s experience is related to their barbell velocities. This is an important and previously unexamined aspect of VBT. Zourdos showed that, with experienced lifters, within-set variation of velocity was diminished as %1RM increased. This finding is crucial to understand- a more experienced lifter does not experience as much variation in velocity as an unexperienced lifter at near maximal loads. As I mentioned, this has not been shown before in the literature- so my question is, “What else don’t we know about VBT?”

One of the more commonly used VBT methods in strength and conditioning is to observe the between set velocity. What this means is how the average velocity changes from set 1, to set 2, to set 3, and so on- and making adjustments based on that. A coach may conclude, “Well your velocity is stable across all sets, meaning we picked the correct load today.” However- do you always want consistent velocities? What about a heavy training session- shouldn’t your last set have lower velocity than your first set? Some also use a ‘maximum and minimum’ velocity approach, which looks at your best and worst velocity within a set. The difference between them is proposed to provide feedback for the coach about the training session. However, looking at average velocity of a complete set OR comparing maximum and minimum velocities might only be giving coaches a small part of the bigger picture.

Coaches may want to consider observing rep-to-rep velocity as an alternative or complementary method to implementing VBT. The value of looking at every repetition is you get a more complete picture of the training session. It’s not that you shouldn’t consider average set velocities or that you shouldn’t care about maximum/minimum velocities- rather it’s that you should be looking at the trends within a set before drawing any conclusions. An example from a real athlete training session:

Let’s get some information about the training session:

  • The day’s volume is 3x5 (3 sets of 5 repetitions)
  • The exercise is the back squat
  • The load on the bar is 210 lbs. – this is a moderate load (~85% 1RM) for this individual
  • We are observing average velocity, not peak velocity

Now, let’s examine the results of the 3 types of analysis we’ve talked about in this post. 1) Average set velocity; 2) Maximum/minimum difference; and 3) Rep-to-rep velocity changes:

1) Average Set Velocity

The average set velocity looks like this:

  • 0.64 m/s for set 1
  • 0.66 m/s for set 2
  • 0.68 m/s for set 3

So as a coach, what do you think? The average velocity is clearly increasing per set (and remember- this is supposed to be a moderate weight), so the bar load is too light- let’s increase it for next time. Right? Well, maybe- let’s observe what some of our other analysis shows.

2) Maximum/Minimum Difference

The maximum and minimum velocity values were:

We take these to find the percent-change from maximum to minimum:

  • 43.38% difference for set 1
  • 16.38% difference for set 2
  • 35.06% difference for set 3

Now again, as a coach, what do you think? There are fairly large changes in velocity from maximum to minimum. If you didn’t look at the average set velocities from analysis #1 you might think that the load is too heavy here, right? That wouldn’t be too far of a stretch to draw that conclusion. When you compare these two methods of analysis, conclusions would be difficult to draw as they point to totally different outcomes. What about our third method of analysis?

3) Rep-to-Rep Velocity Difference

There are a variety of ways to look at rep-to-rep velocity:

  • Chronologically meaning rep 1 to rep 2, rep 2 to rep 3, etc.
  • Examine changes compared to the first rep of the set- such as difference between rep 1 and rep 2, between rep 1 and rep 3, etc.
  • Changes compared to the maximum velocity rep
    There are multiple ways to examine rep-to-rep velocity and it hasn’t been tested enough to determine if one way is superior to another. Let’s take a look at the percent changes in the chronological sense:

Let’s take a look at a few stand-out points and try to compare the results to the results of the previous analysis methods.

  • Set 1- we see a fairly consistent increase in velocity across the set, but a large drop on the last rep. Why did that occur? That’s where velocity and the art of coaching have to be combined. Did the athlete’s technique change or become impaired during the last rep? Did they try to “coast” through the last rep and not give a maximal effort? Whatever the case may be, it seems that the last rep was mostly a misnomer than an indication of ability. When comparing this to the maximum-minimum method, the last rep may be responsible for that large negative % change seen in set 1.

  • Set 2- There aren’t really any LARGE changes from rep-to-rep in velocity. This supports the relatively small % change seen in the maximum-minimum method set 2.

  • Set 3- There are consistent negative % changes in velocity- this indicates that the bar load might be getting a little heavy. If this is a moderate load, this decrease in the third set would be an expected result.

Method 1 indicated that the load was too light, Method 2 indicated the load was too heavy, when you use Method 3 and combine all 3 together you might conclude that the weight is just right. The perfect goldilocks analogy. Further reading on rep-to-rep velocity may be found on a recent conference poster our lab presented- Sato, K.; Carroll, K.M.; Stone, M.H. Examination of Bar Velocity in Barbell Back Squat (presented at the International Society of Biomechanics in Sports 2016 conference in Tsukuba, Japan.

In summary, this isn’t about which method is BETTER than another method. It’s about how to use your data to make a better informed decision about your athlete’s training. There is so much we still don’t know about VBT, so we must continue to examine data from different angles and to keep questioning our current methods. Even more importantly, velocity data should be used as a supplementary tool to your coaching. If you put all of your eggs in the average set velocity basket, without using your knowledge as a coach, you might be making an unfavorable change in your athlete’s training. It’s important to examine your data in more than one way before drawing stern conclusions.

The take home message here is that using rep-to-rep velocity can help fill in the gaps of the data analysis you might already be doing with VBT. Using it in combination with other VBT analysis methods may provide coaches with a more complete interpretation of a training session.