Power Production and Endurance Put to the Test

In a new study, researchers analyzed power output during long sets of back squats.

The ability to exert power repeatedly is important for most sports. In a recent study in the Journal of Strength and Conditioning Research, investigators examined exactly what happens to power output when repeated efforts are demanded.

The researchers in the Journal study wanted to find out what happens to explosive power when it needs to be expressed repeatedly with only short rests. Nineteen trained men performed explosive back squats using only forty percent of their max. They repeated for five sets of sixteen reps. Only two minutes of rest were allowed in between each set. For every rep, power was measured in watts to see what trends might emerge.

The researchers found two statistically significant findings. The first is exactly what you would expect. There was a decline in power within any given set. In other words, from first rep to last, the athlete’s power output waned.

The second critical finding was the opposite of what you may expect. There was no statistical decline in the peak power for each set. Bear in mind here that the rests were relatively short, at only two minutes, and still the peak power didn’t change radically, despite there being five long sets.

There are other interesting results that the researchers didn’t dwell on. If you look at the trends of the peak power, which occurs in the first few reps of each set, there definitely seems to be a decline. Although this result wasn’t statistically significant, it would indicate that extending this protocol even further would likely begin to result in significant peak power losses.

Another interesting aspect of the results that I’m a little surprised the researchers didn’t mention was the different power profile of the first set when compared to the rest. As expected, the shortest decline in performance occurred from first rep of the first set to the first rep of the last set (a 17.9% drop in power versus a 22.3% drop for the final set). Oddly, however, the average power of the first few reps of each set after the first was substantially higher.

In fact, there seemed to be a potentiating effect after the first set. Only the first rep of the first set broke 2,000 watts on average. Then the performance level dropped like a stone for the second and all subsequent reps. The first several reps of the next few sets were also much higher in power output compared to the first set.

The researchers acknowledged that power production peaks in the first few reps of long sets like these, but repeated high performance is possible. Because of this, they recommend this type of training for developing anaerobic endurance for sports involving a lot of repeated lower body power efforts, such as soccer and football.


1. Garrett Hester, et. al., “Power Output during a High-Volume Power-Oriented Back Squat Protocol,Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000484

Photo provided by Miguel Tapia Images and CrossFit LA.