Who of you use velocity-based training (VBT) as part of your toolbox? Realising velocity is an important component of power development, one of the hardest fitness qualities to change, but one of the most desired qualities to possess, velocity development is of great interest to many of us. This article looks at VBT in the context of explosive power development.
Maximising explosive power or the power output very early in a contraction has been a focus of a few posts, so we've been looking at the power-time curves. However, intuitively it makes sense that if we would like to develop explosive power, we should look at trying to shift the force-time and/or the velocity-time curves to the left. That is, we're trying to produce more force or velocity earlier in the contraction. You can see this shift shown as the Pre-Post velocity shift in Figure 1, with more power at 100 ms or post PV-TPV.
To understand how to shift these curves we need tools to give us feedback on velocity and time, two of the more cheaper and well used tools are linear position transducers (LPTs – Gymaware, Speed4lift, T-Force, Tendo-unit) and inertial measurement units (IMUs – Bar Sensei, Push, Beast, Myotest ). In the case of LPTs, the wire is typically attached to a bar, a weight stack or a person via a waist harness, and gives information on displacement over time, which equals velocity. An example of a LPT attached to a bar and a velocity read out is shown in Figure 2.
With VBT most practitioners are interested in either the peak velocity or mean velocity output as a means of determining quantity and/or quality of a workout. In terms of explosive power development however, these measures don’t help us a lot in determining if we're shifting the curve i.e. are we on the mark with our training? We need time series data to get the full picture. For example, in Figure 1 we note no change in peak velocity, and the assumption would be that the training is ineffective, however, not so if we're interested in producing higher velocities per unit time as shown by velocity at 100 ms or Post TPV.
Now I've been having some interesting conversations with Rolf Ohman and Kenneth Riggberger both Track and Field, and Strength and Conditioning coaches and Rolf the founder of the 1080. They've been collecting thousands of files over the years and two of their favourite measures come from the velocity-time curve [peak velocity (PV) and time to peak velocity (TPV)], which provide them a lot of insights into athlete performance and fatigue. That is another story but.
In the context of this article let’s have a look at some squat data of an elite athlete they shared – thanks Rolf and Ken. The peak velocity data of an athlete training with 83 kg concentrically and 103 kg eccentrically over 5 sets of 5 reps can be seen in Figure 3. The goal of the session was to maintain velocity and power throughout the entire workout, which the athlete seems to have achieved given the trendline on the velocity-time graph.
What I really found interesting in this data set was the TPV over the 25 reps for this athlete. The trendline indicates that the TPV was decreasing over the duration of the session. Guess what, the decreases were reflected in the time to peak power graph. Now in terms of explosive power training this type of feedback is invaluable. First this type of feedback is known to motivate athletes and furthermore you know your programs are having the desired effects.
Time series data can motivate athletes and provide valuable insight into the efficacy of your programming, and athlete adaptation. If explosive power development is of interest to you, then monitoring and/or giving athletes time series feedback on the component parts of power (force x velocity) is important. In terms of VBT, most devices provide only mean and peak values, whereas instantaneous feedback on measures such as velocity in 100ms or TPV, are desirable for explosive power development.