The Basis of Hypertrophy

The Question

"How long should I rest for between sets?" "Make sure you only rest for thirty seconds or you're not doing it right!" "Your muscles need 3-5 minutes of rest between every set."

One of the most popular questions dwelling in the roots of the fitness community concerns rest periods between sets of an exercise. This question is asked by all individuals, from those who are about to step into the gym for the first time, to those who are habitual lifters merely seeking scientific proof or affirmation on the topic. I hope to debunk some of the tossed-around "broscience" you may have heard while providing a detailed, yet brief description of the biology behind the different methods and what the most practical avenue is for you to employ.

Terminology

A rest period is what I will classify the amount of time an individual waits for between each successive set of a given exercise. The purpose is quite simple: to give your body enough time to recuperate in order to properly execute the desired amount of repetitions once the rest interval has ended.

It is important to note that different styles of lifting require, or work most effecitvely, with different rest periods. What do I mean by this? If your goal is to master muscular endurance while your friend strives to become a world-renowned powerlifter, each of you will stick to significantly different periods of rest. Therefore, for the sake of consistency, I will lead you to the optimal choice based on hypertrophy, or "gaining muscle."

Rest Periods

Consider three separate durations of rest: thirty seconds or less, a minute to a minute and a half, and three minutes or more.

First, let's consider the shorter rest period of thirty seconds or less. Picture the following. Your aim is to complete four sets of seated shoulder presses for 8-12 reps. You complete 10 reps for your first set. You pull out your phone, hit the timer, and within a blink of an eye, thirty seconds is coming up. Your second set proves extremely difficult to even hit the minimum of eight reps without achieving muscle failure. Once again, thirty seconds is upon you and the realization soon sets in that this shorter rest period may not be practical. The only plausible solution: lower the weight in order to continue in the desired repetition range. This is exactly what science has dictated as well. "30-second rest intervals reduced training volume by more than 50% and marked decreases in load were seen in each subsequent set" (Schoenfeld 76). In short, you are inhibiting yourself. Overall tension on your muscles will be reduced because of the constant lowering of the weight in order to maintain the desired rep range. Understandably, the physiological advantages from the exercise can be and most likely will be overlooked.

Now for the opposite end of the spectrum: resting for three minutes or more. Indeed you will be able to complete all four sets of the exercise within the repetition range that you wanted without decreasing the weight. But, as with most things, at what cost? Does a trade-off exist? The cost is a decrease in primary metabolite accretion due to the time of inactivity and a significant increase in lactic acid build-up. Resting for this long of time also fails to progress the neural activity stimulated from the exercise, meaning that the benefits from the motion will not be diminished during this long of a waiting period.

The third category, resting between a minute and a minute and a half, proves to be the most beneficial in several realms (lactate concentration and acidity, for example). Most important is the ability to continually execute the exercise in the rep range of 8-12 without having to significantly decrease the weight. If weight does in fact have to be lowered, the difference is usually either negligible or innocuous when it comes to recovery and hypertrophic benefits. This rest period has been popularized among the fitness community due to the large amounts of research conducted proving its efficiency.

Conclusion

Here is the main takeaway from the blog: the optimal rest period is the minimum time of inactivity your body needs before completing successive sets in a continued rep range without having to decrease the load. Obviously, physiologically we are all different and I cannot assume one stringent rest interval is perfect for every person, but resting between a minute and a half and two minutes appears to be the most beneficial for gaining muscle after personal research.

There are countless advantages to all rest intervals; I highly encourage you to do some independent research as you may find that your fitness goals call for something other than what I have mentioned.

Thank you for the read! If anyone has constructive criticisms or compliments, please feel free to comment. If you enjoy these fitness blogs let me know!

Bibliography
Schoenfeld, Brad. “Chapter 3.” Science and Development of Muscle Hypertrophy, Human Kinetics, 2016, pp. 76–78.