To understand this study, it’s helpful to take a closer look at the data on the similar changes in muscle size and strength between groups and how these findings relate to those of previous studies.

In the group that took a break (referred to as periodic training below), muscle size and strength decreased during the 10-week detraining period, which is to be expected. Other studies have found that muscle size and strength are generally maintained over about 2 to 3 weeks of detraining,^[1]^[2]^[3]^[4]^[5] but over longer periods, significant decrements in muscle size and strength occur, with typically greater decrements reported for muscle size than strength.^[1]^[6]^[7]^[3]^[8]^[9]

In this study, the decreases in muscle size and strength during the detraining period were as follows:

Leg press 1-repetition maximum: −5.4%
Biceps curl 1-repetition maximum: −3.6%
Vastus lateralis cross-sectional area: −9.9%
Biceps brachii cross-sectional area: −7.3%

For comparison, studies in young, untrained men that involved 7 to 8 weeks of resistance training followed by 7 to 8 weeks of detraining reported a 4.6% to 5.4% reduction in quadriceps size during the detraining period.^[8]^[10] Additionally, 8 weeks of detraining resulted in a 22.6% reduction in Smith machine half-squat 1-repetition maximum.^[8]

With respect to the retraining period, the summarized study found that the magnitude of increase in 1-repetition maximum leg press and vastus lateralis and biceps brachii size during the first 5 weeks of the second 10-week training period was greater with periodic training than continuous training. This faster rate of gain with periodic training is what ultimately led to the lack of differences between groups at the end of the study.

Changes in muscle size and strength with periodic resistance training (PRT) compared to continuous resistance training (CRT)

PRT = periodic resistance training; participants performed resistance exercise for 10 weeks, took 10 weeks off, and performed another 10 weeks of resistance training. CRT = continuous resistance training; participants did not perform resistance exercise for 10 weeks, and then performed 20 weeks of resistance training continuously.

Notably, the finding of accelerated gains in muscle size and strength during the retraining period is supported by other studies.^[11]^[10]^[12] Like the summarized study, another study in young, untrained adults that involved 10 weeks of resistance training, followed by 20 weeks of detraining, also found that it only took 5 weeks to regain the muscle size and strength lost during the detraining period.^[9]

These results have led to interest in the strategic use of short periods of training cessation to bolster muscular adaptations. The idea is that these periods aren’t long enough for reductions in muscle size and strength to occur, but they’re sufficient to resensitize skeletal muscle to the anabolic effects of resistance exercise.^[13] Thus, they provide the benefit of accelerated gains in the subsequent training period, without the need to spend time regaining lost muscle size and strength. However, the available evidence does not support this theory.

Several studies have evaluated changes in muscle size and strength between a group who performed continuous resistance training and a group who performed a similar amount of resistance training but took a 1 to 3 week break in the middle of the intervention. All of these studies have reported that changes in muscle size and strength were similar between groups.^[13]^[5]^[12]^[14]

It also bears mentioning that in the summarized study, although gains in muscle size and strength were faster in the periodic training group than the continuous training group during the first 5 weeks of the second 10-week training period, the rate of gains in the periodic group during the first 5 weeks of the second 10-week training period was not greater than the rate of gains during the first 5 weeks of the first training period.

Collectively, these data indicate that the accelerated gains in muscle size and strength following detraining only pertain to regaining what was lost. Short periods of training cessation do not seem to augment new muscular adaptations in the following training period.

To conclude, taking a couple or even a few weeks off from resistance training is fairly inconsequential to muscle size and strength. Significant decrements in muscle size and strength will occur during longer detraining periods, but whatever is lost can be regained relatively quickly, perhaps in half the amount of time it took to gain it in the first place.

The available evidence indicates that taking an extended break in the middle of a resistance training program is not detrimental to longer-term muscular adaptations accrued over about 6 months. However, these results are not necessarily generalizable to longer durations. If the interventions applied in the summarized study were extended over a few years, it would be very surprising if taking 10 weeks off from exercise after every 10-week training period produced the same gains in muscle size and strength as training regularly throughout the same timeframe.

In the context of maximizing gains in muscle size and strength over a lifetime, it’s plausible that the less time spent regaining lost muscle size and strength — and thus the more time spent building new muscle size and strength — the better. As such, during times when resistance training is of low priority, whether due to traveling, vacationing, low motivation, or other reasons, it’s probably best to just decrease training frequency and training volume, as opposed to not performing any exercise at all.

According to data from a couple of studies, reducing training volume by 50% to 66% of what was previously completed (e.g., performing approximately 3 to 5 sets per muscle group per week instead of 10 sets) while maintaining training intensity is sufficient to maintain — and sometimes even increase — muscle size and strength.^[15]^[8]

How does taking a break from resistance exercise affect strength and muscle gains? Original paper