Strength Training Does Not Increase Critical Power
Despite endurance sports being steeped in a tradition that is opposed to strength training, time and time again strength training has proven to be effective for endurance athletes. In a recent study published in the Journal of Strength and Conditioning Research, investigators looked at the role of a variable called critical power as a means of explaining the relationship between strength and endurance.
Critical power is a variable that represents the maximum sustainable output of power and energy. It is the balance point between maximal power output and maximal endurance. An action that reaches beyond critical power cannot be sustained for long, and this applies to many athletic realms, like short distance sprints and even weight lifting.
Because critical power is the line between both power and endurance, it’s considered to be useful for testing performance. Since the goal of most distance races is to achieve the fastest time, critical power seems especially important for competition, since it’s the speed at which you will achieve the greatest results. Strength is also a part of the critical power equation. More strength means higher critical power, and may also improve pace for marathon runners and other endurance athletes.
In this study, the researchers found there were some changes in performance on an exercise bike after eight weeks of strength training. The power which the participants could maintain at their VO2 max was higher after strength training, and their time to exhaustion was longer as well. Interestingly though, their critical power remained largely the same, and in some cases actually dropped. The researchers speculated that their method of determining critical power was not ideal for predicting changes in performance.
There are a few finer points to consider in this study. The participants were recreationally active, but had not engaged in either strength training or more than two days of endurance training weekly for at least a year. This is important to note, because these sorts of trainees usually respond rapidly to strength training and may have different results than trained athletes. In fact, the study participants did get about thirty percent stronger than the control group, which was a big improvement over just eight weeks of training.
Another interesting factor was the exercises chosen. The exercise plan was fairly traditional. It included exercises like the squat and bench press, performed three times per week for three sets of eight. While it’s no surprise these athletes got stronger, it’s also not odd that they did not increase critical power, which depends more on technique and takes more time to develop.
This study reminds us that strength training is indeed a good thing, even for endurance athletes. However, the reasons why might be different than we thought.
1. Brandon Sawyer, et. al., “Strength Training Increases Endurance Time to Exhaustion During High-Intensity Exercise Despite No Change in Critical Power,” Journal of Strength and Conditioning Research, 28(3), 2014
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