Interset Rest Time
“Bro, 10 second rest is the best; it keeps the pump going.”, is just one example of the number of conversations you might hear in the gym as people discuss rest time. Well, in this article, we will put a little science behind the madness of bro-talk. We will discuss what the best rest time is for hypertrophy, as well as strength, and we will, of course, cover the physiology of the advantages. So, without further ado, let’s jump into it.
What is Rest Time?
So we are on the same page, we are defining “rest time” as the time of no activity between one set to the following set in the same muscle group. We are not discussing rest between training sessions.
Rest Time: Strength Training
Strength training, as we are defining it here, is the training to increase weight lifted between sessions, not necessarily for muscle growth. So, a person might lift 225lbs (102kg) on squats one day and the next week, they aim to lift 230lbs (~104kg) – that is strength training, simplistically.
Now, how does rest time play into this? Well, there are a number of studies that have examined this, and the answers are a bit more nuanced than one might imagine. First off, it does depend on your goals. If you are training for powerlifting, you may be more concerned with your 1 Repetition Maximum (1RM), and if you are training for strength, in general, you may be more concerned with a 5 Repetition Maximum (5RM) or another repetition maximum. So, we will need to examine each individually to be accurate.
1 Repetition Maximum
After investigation of 1 minute, 3 minute, and 5 minute rest times between sets, there is no evidence showing much difference between conditions . Now, there is no statistical difference, but I would venture to say there may be a slight benefit, in terms of reliability of performance, using 3 or 5 minute rest times. I concur with the researchers postulating that due to the extreme nature and need for higher level coordination of a 1RM, it might be beneficial, psychologically, and even physiologically to aim for 3 minutes or even 5 minutes (but, I tend to lean toward around 3 minutes) .
So, in a 1RM test, you can rest as little as 1 minute (likely not much less) and even as much as 5 minutes (or more) and you will still maximize performance.
5+ Repetition Maximum
This section encompasses repetition in the 5-15 range, so there may be a bit of variability in results depending on the exact repetition range being used. Again, conditions measured were largely between 1, 3, and 5 minute rest intervals, so we will use this as our base.
It seems clear that when doing repeated sets, regardless of the number of sets, or even the number of repetitions used, is best performed with more rest . 1 minute is significantly less effective, seeing a massive drop off in performance; as much as a halving effect on repetitions finished on subsequent sets . 3 minutes is a considerably better recovery time as it allows for only, roughly, a 30% drop in performance between the initial set and the subsequent set, with up to a 60% drop in performance by the 5th set . Still, this is at least a 10% improvement by comparison to 1 minute rest in identical sets. Then, a 5 minute rest shows the best performance, with only a 2-13% drop in performance from the initial set to the subsequent set and a -25% drop in performance between the initial set and the 4th set . One note, it seems that more experienced lifters may be able to sustain higher performance output, even at 3 minute intervals; this is not the case for beginner or intermediate lifters (possibly elderly, as well?) .
So, can we conclude a 5 minute rest time is the best for repeated sets and numerous repetitions? Almost, but not quite. Luckily, these studies have been done in different muscle groups, which helps give accuracy in our interpretation, but since only 5 minutes was measured, we do not know if longer rest times would lead to even better recovery between sets. I would imagine that 5 minutes is a good bench mark, and a person could probably go up to 6 or 7 minutes, but eventually, the risk of the muscle belly cooling or some other small physiological change (or even psychological shift, distraction) could impede increased benefit. So, overall, although longer than 5 minutes may be acceptable and it has not been measured, 5 minutes is a solid foundation to work off.
Rest Time: Muscle Hypertrophy
In the case that you may be vying for greater muscular size, there is some interesting research considering this goal. There is evidence that longer rest times of 3 minutes compared to 1 minute (or less) are more beneficial, or at least comparable, to shorter rest times . If volume is equated, there may not be a difference between conditions, but if left to the training design (3 sets x 8-12 repetitions), the overall volume ends up being higher in the longer rest interval group, because the low rest interval group will achieve only the lower repetition numbers on that range, consistently . Granted, again, this can be equated for, but it is telling of the situation, as 30-60 second rest periods may not allow for sufficient recovery between sets to accrue sufficient volume to lead to equal hypertrophy on an inflexible program .
Overall, as I mentioned, if a training session asks for 3 sets of 10 repetitions, and you employ a 1 minute rest time one day and a 3 minute rest time the next workout, it may be that you will have a training scheme along these lines:
1 Minute Rest
150lbs x 10
150lbs x 8
150lbs x 6
3 Minutes Rest
150lbs x 10
150lbs x 9
150lbs x 8
So, the total volume will be higher in the longer rest, leading to, presumably, more muscle growth, because we know lower rest time (from the previous section) leads to lower repetition numbers in subsequent sets. Again, however, this can be easily fixed by simply making up the difference using basic training principles.
So, in all, it doesn’t matter much if you know what you are doing.
Understanding the Physiology
This is the section where we get to posit possible physiological explanations for the results discussed in previous sections.
A lot of the above information, favoring longer rest times, is easily understandable, and some is a bit more confusing, but still explainable. When resting, the cells metabolize what lactate is produced to either produce more glucose or to be oxidized for energy . However, the cell also resynthesize creatine phosphate via the creatine kinase reaction . This time of inactivity post-set is crucial for both of these processes, as well as other, including pH balance from the dissociation of hydrogen ions .
So, how does this play into the discussed scenarios?
Well, when it comes to the one repetition maximum, why does a one minute rest live up to its bigger brothers?
It comes down to the lack of lactic acid being produced. The use of ATP is obvious, but because the set is made up of a single repetition, the lift lasts a short period of time (less than 10 seconds), so the entire energy requirement can be fulfilled by the phosphocreatine system, leading to less reliance on the glycolysis system. So, although the PCr system normally takes around 4 minutes to completely replenish, we might imagine that the entire store is not used, and the next repetition will also not use the entirety of the store, so any replenishment of said system in that 1 minute is sufficient to produce force able to repeat the repetition.
Now, how about in the case of multiple repetitions?
This is a situation in which both factors play a commanding role. The set is long enough to require more than the phosphocreatine system has to offer, so the PCr system is exhausted, so the cells rely on the glycolysis system to produce needed energy. As that is the case, and the exercise is anaerobic in nature, we can expect an accumulation of lactic acid. As this is the case, when resting, the muscle dissociates lactic acid to its product parts (lactate and hydrogen). If the rest time is long enough, more lactate can be shuttled, as well as hydrogens expelled from the body through the bicarbonate system. If the rest time is not long enough, insufficient amounts of recovery in the PCr and hydrogen (acidosis) buffering systems prevent the muscle from producing similar amounts of force, so the repetitions are cut shorter and shorter of the original set performance.
In any of these situations, if a person is better trained with much more experience, their recovery may be shorter due to a more efficient dissociation, lactate shuttle, and PCr recovery.
Some have theorized that, because there is an increase in Human Growth Hormone (HGH) with shorter rest times, that this will lead to more muscular growth long term, but the evidence is lacking as there is some proof that HGH seems to be the same between conditions after several weeks. I found it interesting, but it likely does not play as significant a role as once thought, in this context.
So, all that said, it seems that, generally, longer rest times are more advantageous; that is not to say a short rest time cannot be effective, just not as effective in certain situations. If you prefer shorter rest times or are short on time, expect your strength to decrease per set, and the muscle mass grown will be decreased unless you complete additional work to equate.
Writer: Nicolas Verhoeven
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