By: Danny Raimondi
Most coaches are aware of the theory behind post-activation potentiation, also known as post tetanic potentiation. I first read about this in article by Charles Poliquin in which he discusses the “1-6 method”. Intuitively, the method makes sense, and if you ever decide to try it out, it probably will work. To perform the method, for example, take a heavy squat, perform 1 repetition, drop the load, and perform 6 repetitions. The next series take a heavier single and a heavier set of 6. Repeat this process usually for 3-4 series. The biological rationale behind the improvements you’ll most assuredly gain on the subsequent set of 6 has to do, in theory, with the nervous system.
Potentiation doesn’t end there, however. Research has also examined the effects of strength training exercises on subsequent low load, high velocity activities. Squat a heavy weight, go run a sprint, and see if there is any improvement. Granted, I’m grossly oversimplifying the process (I’m not accounting right now for rest times, percentages of certain lifts, training age, etc…), but we’ll leave that for later.
In a recent study by Bullock and Comfort (2011), the authors examined the effects of 2, 4, or 6 depth jumps on squatting performance. Using a randomized control study, 14 males tested their maximal squat 5 times with at least 3 days of rest in between. The subjects performed depth jumps from a height of approximately 12 inches followed by a maximal effort squat to 90 degrees of knee.
The authors found that performing either 2,4, or 6 repetitions of the depth jump approximately 4 minutes prior to a maximal effort squat will yield significant (p<0.001) results. While the researchers note that there was no significant inter-repetition difference (i.e. performing 2, 4 or 6 didn’t yield any significant results), there was a greater potentiation effect trend using 6 depth jumps among stronger (squat greater than or equal to 2x bodyweight) athletes. It ultimately depends, as the authors concluded, on the rest between exercises and the volume of jumps with respect to the athlete’s training level.
Now for the limitations of this study, because there’s always going to be some confounding variables. The authors used a fairly small population (14 subjects with a moderate amount of training experience). Consider, however, the nature of research and funding in exercise science. While the population seems small, it’s not uncommon to see small sample sizes when money is hard to come by. Obviously the question of training experience also comes into play. Some athletes were demonstrably stronger than others, and may have greater neural ability (i.e. rate coding, motor synchronization, etc…) during the squat and depth jump movements. These same individuals may be more likely to respond to higher volumes, whereas lesser trained individuals would really respond to any extra stimulus.
One of the major limitations of the study, I believe, was the manner in which depth jumps were performed. The researchers used a 12 inch box, which, albeit, isn’t very high. For the training experience of this group, however, it may have been sufficient. The real kicker in this study is that the authors, to control for arm swing, had the athletes perform the jumps with their hands on the hips. This greatly reduces jump height and technique. Ground contact time, force production, and jump height are all compromised when removing the hands from the equation. One could make a case that the manner in which the researchers tested the squats is also a limitation, but I think that’s secondary to the performance of jumps.
So what’s the take home message for physical preparation coaches? Well, the research is by no means definitive. There are still many confounding variables that can explain why the athletes did better. As a coach you obviously must account for an athlete’s ability and the context in which you’re applying the stress ( i.e. what time of the year, what outcomes are you hoping to achieve, etc…). You might consider adding low load, high velocity movements, such as drop squat jumps, in the warm up prior to heavy squat days in order to potentiate the latter. One must simply remember that more intense means, such as high depth jumps performed for relatively high volumes (≈ 10 or more jumps in a series) probably require priority in a workout and may not be best when paired with squats.
As the late Yuri Verkhoshansky said, depth jumps are one of the final stages in the process of developing explosive power. Or, to paraphrase a teacher of mine here at the U, it’s like showing an athlete all your cards. It might be better to save depth jumps and more intensive means for those who will respond better when the time comes. If you “waste” the movement on a low level athlete, the adaptation that could have been achieved might be diminished. Ultimately, as this and many other studies have supported, potentiation seems to be an effective method of improving various abilities (explosive power, maximal strength, decreased ground reaction time, etc…). Anecdotally, and this can be just as important as the formal research, many people have touted the benefits of coupling exercises in a ‘complex’ fashion. Before running out and doing depth jumps every squat day now, though, be sure that as a coach you understand what adaptation you’re looking to achieve, when you want to achieve it, and who you’re applying it to.
Bullock, N. & Comfort, P. (2011). An investigation into the acute effects of depth jumps on maximal strength performance. Journal of Strength and Conditioning Research, 25(11), 3137-3141. DOI: 10.1519/JSC.0b013e318212e224.