The kettlebell swing is an exercise often used in high reps to get the heart rate going and to burn calories. And for anyone who has ever done a swing, you’ll know it’s also an intense posterior chain exercise as well. The effects of the swing were recently examined by researchers in a study published by the Journal of Strength and Conditioning Research.
In this study, ten male participants performed twelve rounds of thirty seconds of kettlebell swings with a 24kg kettlebell, followed by thirty seconds of rest. Blood work was examined before the exercise, immediately afterwards, fifteen minutes after, and finally thirty minutes after. Heart rate and perceived exertion were taken throughout.
Now bear in mind, this was not a comparative study. There was no examination of how these changes in hormone levels actually look against, say, a squat or other exercise that challenges similar muscles. As such, the purpose was not to determine if the swing was superior to other exercises, but rather if it was a valid addition to a weight training program on its own.
And indeed, it was a good addition. Immediately following the swings, testosterone levels were raised by fourteen percent. While this is a significant amount, it isn’t huge, but bear in mind that the exercise protocol wasn’t with particularly heavy weights, but rather was more cardiovascular in nature. As a result, the testosterone returned nearly to resting levels after fifteen minutes and then was actually lower than resting levels at thirty minutes.
Cortisol was also elevated, which is a typical response to exercise. Although many athletes seek to minimize this catabolic hormone, it is commonly at some of its highest levels post-exercise, since cortisol responds to any stressor. In fact, it was elevated by about 45% as a result of the swings. It took the full thirty minutes of testing before it had returned close to normal.
Growth Hormone Response
Growth hormone, which is heavily involved in fat metabolism, was elevated as well. This is also a normal response to exercise. It shot up eighteen times its resting level immediately following the protocol, which is not odd at all since resting levels of growth hormone are usually low. It then continued to rise to 21 times resting levels after fifteen minutes, then to sixteen times after thirty minutes.
Lactate levels mirrored cortisol response. Considering lactate levels are one of the stressors that cortisol responds to, this correlation makes sense. It shot up a little over six times normal levels at the after exercise, followed by a steady decline almost returning to normal after thirty minutes.
Heart Rate and Perceived Exertion
Heart rate and perceived exertion steadily increased throughout each set, which indicates that the athletes may have become exhausted if more sets were included. The participants averaged a heart rate of 57 beats per minute (BPM) prior to the testing, which is pretty low, and ended up averaging 170 BPM by the end.
Kettlebell swings done with a light to moderate weight for time demonstrated a spike in hormones responsible for exercise adaptations. The researchers concluded that kettlebell swings would make a good addition to any program. I’ll add that at an intensely aerobic output spread out over twelve minutes, it’s a decent way to get some cardio in as well.
1. Ronald Budnar, et. al., “The acute hormonal response to the kettlebell swing exercise,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000474
Photo courtesy of CrossFit Impulse.