Short rests or long rests – which is better for maximizing muscle growth?
Table of Contents
Traditionally, short rest intervals were believed to be optimal for building muscle.
Indeed, A 1987 study by Kraemer et al. found that bodybuilders used around 10 to 90 seconds of rest between sets. This was in contrast to powerlifters, who rested around 120 to 140 seconds between sets.
Even today, if you follow any social media general fitness pages, or have read any classic personal training textbooks, you may have come across the notion that shorter rest periods (30 seconds to 2 minutes) are superior for muscle growth, whereas longer rest periods (2 minutes or more) are better for building strength.
The idea shorter rest intervals are superior for building muscle does have origins in scientific research.
Research has shown that when using shorter rest intervals, anabolic hormones (mainly growth hormone) are elevated significantly more than using longer rest intervals. It’s speculated that the greater acute elevations in anabolic hormones would result in greater muscle growth.
However, there are limitations with this. The main problem is that we cannot necessarily assume that just because something induces a greater acute hormonal response, it will cause greater muscle growth.
Interestingly, when looking at the current research, greater acute anabolic hormone elevations do not appear to be correlated to muscle growth. As a result, the idea that short rest intervals produce greater muscle hypertrophy due to the greater acute hormonal response is not supported.
As opposed to looking at research assessing the acute hormonal responses to various rest intervals, it would be much better to look at research assessing measures of muscle growth before and after a set duration in groups using different rest intervals.
Let us evaluate this research.
Evaluating the Research
Interestingly, the weight of the current evidence suggests that for compound exercises, longer rest intervals may be superior to shorter rest intervals for building muscle.
Compound exercises involve the movement of two or more joints, resulting in multiple muscle groups being trained. Examples include the back squat, deadlift, bench press, pull-up, row, and many others.
A 2020 study by Longo et al. had 28 untrained individuals perform leg presses for 3 sets to failure (the point at which no more repetitions can be performed) with an 80% one-rep max load, twice per week for 10 weeks. Increases in quadriceps cross-sectional area were superior when resting for 3 minutes between sets compared to resting 1 minute between sets.
A 2016 study by Schoenfeld et al. had 13 men with at least 6 months of training experience perform a range of exercises each for 3 sets to failure with an 8-12 rep max load, three times per week for 8 weeks.
The exercises performed included the back squat, leg press, leg extension, bench press, overhead press, lat pull-down, and cable row.
Except for the leg extension, all of these exercises are compound.
Increases in elbow flexor, triceps brachii, anterior quadriceps, and vastus lateralis thickness favored the group resting for 3 minutes compared to the group resting for 1 minute between sets.
A 2009 study Buresh et al. split 12 men with some training experience (but not in the 3 months before this study) into a group resting 2.5 minutes between sets or a group resting 1 minute between sets.
Both groups trained four times per week for 10 weeks, with workout 1 and workout 2 repeated twice per week (image below), a range of compound exercises were used.
The group resting 2.5 minutes between sets experienced greater increases in thigh cross-sectional area and arm cross-sectional area.
A 2017 study by Fink et al. split 14 untrained individuals into a group resting 30 seconds between sets or a group resting 2.5 minutes between sets. Both groups trained the bench press and back squat for 4 sets to failure with a 40% one-rep max load, twice per week for 8 weeks.
Some of you may be questioning the use of a 40% one-rep max load. However, for hypertrophy, this is perfectly fine. The current evidence suggests that loads between 30% and 85% one-rep max produce similar hypertrophy, provided reps performed to failure.
Increases in triceps cross-sectional area were similar between both groups. But, increases in thigh cross-sectional area favored the group resting 2.5 minutes between sets.
There actually is one paper finding shorter rest intervals to be superior for muscle growth with compound exercises.
A 2015 study by Villanueva et al. split 22 untrained elderly men (their average age was 68 years old) into a group who rested 1 minute between sets or a group who rested 4 minutes between sets.
Both groups performed the leg press, machine chest press, lat pulldown, seated row, dumbbell step-ups, dumbbell Romanian deadlifts, knee extensions, and leg curls for 2-3 sets with 4-6 reps, three times per week for 8 weeks.
Increases in lean body mass were superior for the group resting 1 minute between sets.
However, this study does have limitations. Firstly, the subjects were elderly men. Later on in this article, we will explore how age impacts recovery between sets.
Secondly, and more importantly, volume load (the product of sets x reps x load) was equated between the 1-minute rest group and 4-minute rest group. This would have meant that the 1-minute rest group was training closer to failure.
To illustrate this, let’s say your one-rep max on the bench press is 100kg and you had to perform 3 sets of 8 reps with 75kg. Which would be more difficult, resting 1 minute between sets or resting 4 minutes between sets?
Of course, resting 1 minute between sets would be harder, as you would be training closer to failure on your subsequent sets, thanks to the decreased recovery time.
Therefore, it’s unclear what the results of the Villanueva et al. study would look like if both the 1-minute rest group and 4-minute rest group took their sets to failure.
Remember, the 3 studies we have looked at so far finding greater hypertrophy for longer rest intervals had subjects take their sets to, or close to, failure.
So, the current evidence suggests that when subjects train with the same training program, and with the same effort (proximity to failure), longer rest intervals (2.5-3 minutes) seem to produce greater hypertrophy than shorter rest intervals (1 minute or less) with compound exercises.
The same training program detail is worth elaborating on. The same training program would imply that a longer rest group and shorter rest group perform the same number of sets.
Interestingly, there is some evidence suggesting that if you use shorter rest intervals, performing more sets may be compensatory. Meaning that more sets and shorter rest intervals could produce similar hypertrophy to fewer sets and longer rest intervals.
Returning to the Longo et al. study, they found that when subjects trained twice per week for 10 weeks, performing 4 to 5 sets to failure on the leg press with an 80% one-rep max load and 1 minute of rest between sets produced similar increases in quadriceps cross-sectional area to performing 3 sets to failure on the leg press with an 80% one-rep max load and 3 minutes of rest between sets.
A 2005 study by Ahtiainen et al. found that resting 2 minutes between sets produced similar increases in quadriceps cross-sectional area to resting 5 minutes between sets, when participants performed on average, 1 more set when resting 2 minutes between sets.
Although, 2 minutes of rest between sets would not be seen as a short rest interval to many people. Another way one could potentially interpret this study is that despite the more sets, 2 minutes of rest between sets could be sufficient, and resting for longer may not be required.
Unfortunately, I’m not aware of any other papers comparing 2 minutes of rest between sets to other longer rest intervals for hypertrophy.
As a result, we can only conclude that based on the current evidence, with all else equal, longer rest intervals (2.5-3 minutes) produces greater hypertrophy than shorter rest intervals (1 minute or less) with compound exercises.
However, when all else is not equal, this might not be the case. Specifically, performing more sets (1 or 2) with shorter rest intervals may be able to produce similar hypertrophy to longer rest intervals.
Unfortunately, the evidence is less clear on how long you should rest with isolation exercises.
Isolation exercises primarily involve movement at one joint, resulting in primarily only one muscle group being trained. Examples include biceps curl, triceps pushdowns, lateral raises, leg extensions, leg curls, and many more.
Returning to the Buresh et al. study, a range of isolation exercises were used (highlighted in the image below). As already mentioned, increases in arm and thigh cross-sectional area were greater for the group resting 2.5 minutes between sets compared to the group resting 1 minute between sets.
Therefore, this study implies longer rest intervals are also favorable with isolation exercises. However, it could be argued that the use of compound exercises in the study somewhat confounded our ability to truly deduce if longer rest intervals are better with isolation exercises.
What about the research evaluating rest intervals with isolation exercises exclusively?
A 2016 study Fink et al. had 22 individuals perform three biceps (biceps curls, preacher curls, and hammer curls) and three triceps (close grip bench press, triceps skullcrushers, and dumbbell extensions) exercises.
All of these exercises are isolation exercises, except for the close grip bench press. But, the close grip bench press was used to isolate the triceps, and so this is not really a problem.
The researchers had one group perform those exercises with a 20 rep-max load and 30 seconds of rest between sets and another group perform them with an 8 rep-max load and 3 minutes of rest between sets.
Both groups took their sets to failure and performed the same number of sets (for some reason, the paper does not state the number of sets performed), twice per week for 8 weeks.
Increases in arm cross-sectional area were statistically similar between both groups. However, looking at the percentages, the results favor the group using a 20 rep-max load and 30 seconds of rest. Therefore, this study seems to suggest that with isolation exercises, shorter rest intervals may be superior.
Unfortunately, the load was not controlled. The group that rested 30 seconds between sets used a 20 rep-max load with their sets, while the group that rested 3 minutes between sets used an 8 rep-max load. It could be argued that this somewhat confounded the study.
However, recall earlier I mentioned the current evidence suggests loads between 30% and 85% one-rep max produce similar hypertrophy when reps are performed to failure. This information would imply that the use of different loads should not matter.
Another study by Okazi et al. actually aimed to determine the effects of drop set training with dumbbell biceps curls on elbow flexor hypertrophy.
The researchers assigned each arm of 9 untrained men to one of three conditions: 3 sets to failure with an 80% one-rep max load and 3 minutes of rest between sets, 3 sets to failure with a 30% one-rep max load and 90 seconds of rest between sets, or a drop set condition.
The drop set condition had the arm perform an initial set to failure with an 80% one-rep max load. Immediately after, they performed 4 drop sets to failure with a 65% one-rep max load, 50% one-rep max load, 40% one-rep max load, and lastly a 30% one-rep max load to failure. The below image depicts the flow of events.
All three conditions involved training the unilateral dumbbell biceps curl, two to three times per week for 8 weeks.
Increases in cross-sectional area of the elbow flexors (which included the biceps brachii and brachialis) were similar between all three conditions.
Therefore, this study implies that with isolation exercises, rest intervals may not matter at all. Not only did 3 minutes of rest produce similar growth to 90 seconds of rest, but virtually no rest between sets (the drop set condition) was not any worse.
Now, the drop set condition did technically perform 5 sets, which is 2 more than the other two conditions. More sets generally result in more growth, and so this could have helped the drop set condition out.
So, as we can see, the current evidence is completely conflicting with regards to rest intervals and isolation exercises. With one paper finding longer rest intervals to be superior (Buresh et al.), another finding shorter rest intervals to be superior (Fink et al.), and even one finding no difference between various rest intervals (Okazi et al.).
To muddy the waters even further, there is one paper finding no rest between sets (drop set training) to be superior to traditional training for hypertrophy when using an isolation exercise.
Fink et al. split 16 men (untrained in the last year) into a drop set group or normal set group.
Both groups trained the triceps pushdown, twice per week for 8 weeks.
The drop set group performed a single set to failure with a 12 rep-max load, immediately decreasing the load by 20% each time failure was reached 3 times in a row. The below image depicts the flow of events for this group.
The normal set group performed three sets to failure with a 12 rep-max load and 90 seconds of rest between sets.
Although increases in triceps cross-sectional area were statistically similar between both groups, the results do favor the drop set group.
In this study, the drop set group did technically one more set to the normal set group. Similar to the Okazi et al. study, this could have helped out the drop set condition.
Given the conflicting and murky evidence, we don’t really have any grounds to conclude if short rest intervals or long rest intervals are better for hypertrophy with isolation exercises. I think it sensible to suggest that one should aim to rest however long they feel is comfortable and practical with these movements.
Why Longer Rest Intervals May Be Better for Compound Exercises
Although we were unable to conclude if longer or shorter rest intervals are preferred with isolation exercises, we did conclude that with compound exercises, the current evidence suggests longer rest intervals are favorable.
Why might longer rest intervals produce greater hypertrophy than shorter rest intervals with compound movements?
Some researchers have suggested this is because longer rest intervals allow for a higher volume load (the product of sets x reps x load).
For instance, in the already mentioned Longo et al. study, they measured the volume load completed over the 10 week duration. In the two conditions performing 3 sets on the leg press twice per week for 10 weeks, total volume load was higher in the condition that rested 3 minutes between sets versus the condition that rested 1 minute between sets (133,614kg vs 96,392kg).
The authors contended that this higher volume load accumulated with the 3-minute rest condition explained the greater muscle growth observed with this condition.
However, this assumes that higher volume loads result in more growth. When overviewing the rest of the research, this isn’t the case.
Now, to be clear, volume, in the form of weekly sets, is related to hypertrophy. For instance, a meta-analysis by Schoenfeld et al. found that with all else equal, the more sets (that are to or close to failure) performed per week, the greater the muscle growth.
But, the number of weekly sets (to or close to failure) performed and volume load is not the same thing.
Remember, in the Longo et al. study, both the 3-minute rest condition and 1-minute rest condition involved 3 sets to failure on the leg press each session.
In other words, the number of sets to failure was equated between the conditions. But as just mentioned, volume load was higher for the 3-minute rest condition.
Here’s the important point: we have strong evidence volume load is unrelated to muscle growth.
This comes from the research on rep ranges.
As already mentioned, loads between 30% and 85% one-rep max appear to produce similar muscle growth, provided reps are taken to failure.
Based on this information, performing 3 sets to failure with an 80% one-rep max load should produce similar muscle growth to performing 3 sets to failure with a 60% one-rep max load.
Let’s say an individual’s one-rep max is 100kg on an exercise.
When performing 3 sets to failure with an 80% one-rep max load (80kg), assuming a longer rest interval, we might expect them to get 7 reps on the first set, 6 reps on the second set, and 5 reps on the last set. This would give us a volume load of 4,320kg (3 sets x 18 reps x 80kg).
When performing 3 sets to failure with a 60% one-rep max load (60kg), assuming a longer rest interval, we might expect them to get 15 reps on the first set, 13 reps on the second set, and 11 reps on the last set. This would give us a volume load of 7,020kg (3 sets x 39 reps x 60kg).
As we can see, if volume load was an indicator of muscle growth, we would expect 3 sets with a 60% one-rep max load to produce greater hypertrophy than 3 sets with an 80% one-rep max load. But based on the research on rep ranges (and most people would probably intuitively feel this), both protocols would likely produce similar hypertrophy.
Therefore, we have good evidence that volume load is unrelated to muscle growth. Consequently, the idea that longer rest intervals produce greater hypertrophy because they allow for higher volume loads cannot be true.
Moreover, if volume load was the reason, why would this not apply to isolation exercises?
Longer rest intervals would allow a greater volume load with isolation exercises. Yet as established, the research on rest intervals and isolation exercises is conflicting.
A stronger hypothesis behind why longer rest intervals appear to produce greater hypertrophy with compound exercise relates to central fatigue.
Now, I must credit Chris Beardsley, Eric Helms, and James Kriger, from where I initially came across this hypothesis. It was their work that inspired me to research this area much further.
To understand this hypothesis, we first need to understand what central fatigue is.
The reason muscles produce force is because they receive signals originating from the central nervous system. The central nervous system consists of the brain and spinal cord.
There are two neurons involved here, an upper motor neuron and a lower motor neuron.
Upper motor neurons originate in the cerebral cortex, which is the outer layer of the cerebrum. The cerebrum refers to the two hemispheres of the brain. Upper motor neurons mostly end at a region in the spinal cord.
Lower motor neurons mostly start at the spinal cord and end at a muscle.
Upper motor neurons transmit electrical signals to lower motor neurons, which relay this signal to the muscle, causing muscle contraction.
Central fatigue refers to a decrease in these electrical signals to the muscle.
At the level of the muscle, this means that not only do the recruited muscle fibers produce less force, but fewer muscle fibers are recruited overall. This is the opposite of what we want for maximizing muscle growth. We want high levels of muscle fiber recruitment and high levels of force produced by each of those recruited muscle fibers.
During a set on an exercise to or close to failure, central fatigue likely develops.
There are numerous potential mechanisms behind how central fatigue occurs during exercise. One particular mechanism that is linked to hypertrophy training sets is afferent feedback.
Afferents are neurons that transmit information from organs to the central nervous system.
There are sensory nerves linking muscles to the central nervous nervous system. Two of these, group III afferents and group IV afferents, have been associated with central fatigue.
Group III afferents are primarily sensitive to strong levels of muscle contraction, but they do also appear to respond to the accumulation of metabolites.
Group IV afferents are primarily sensitive to the accumulation of metabolites within the muscle, but they also appear to respond to strong levels of muscle contraction.
Just to be clear, the accumulation of metabolites refers to the build-up of various products linked to chemical reactions in the muscle, such as lactate, inorganic phosphate, and hydrogen ions.
When training to or close to failure, the majority of a muscle’s fibers would be producing strong contractions. Additionally, the accumulation of metabolites likely occurs too, especially during higher repetition sets.
In response to these conditions, group III and IV afferents can directly, or indirectly, reduce the electrical signals sent down by lower motor neurons. This means less force production from recruited muscle fibers as well and a reduction in the overall muscle fibers recruited, which, as established, is what we don’t want.
It’s impossible to remove central fatigue during our sets. However, we would want to begin our next set once this central fatigue had disappeared.
This is the basis of the hypothesis, it’s believed longer rest intervals would make it less likely for us to begin a set when central fatigue is still present.
However, why would this particular argument only apply to compound exercises and not isolation exercises?
Some evidence indirectly implies that the more muscle mass involved in an exercise, the greater the central fatigue generated.
Because compound exercises involve a greater amount of muscle mass compared to isolation exercises, this would imply that sets of compound exercises produce greater central fatigue and thus require longer rest intervals compared to isolation exercises.
However, I have come across research opposing this central fatigue hypothesis.
A review paper by Weavil et al. actually suggests that the less muscle mass in an exercise, the greater the central fatigue generated.
An isometric one-arm elbow flexion contraction produced greater central fatigue than one-leg knee extensions. These knee extensions also produced greater central fatigue than cycling.
Out of these three modes of exercise, cycling involves the greatest amount of muscle mass, followed by one-leg knee extensions and then one-arm elbow flexion exercise.
Furthermore, as far as I’m aware, there are no studies investigating how quickly central fatigue disappears after the sets of typical weight training exercises.
But, there is indirect data that would imply central fatigue disappears fairly rapidly.
The below image depicts how long central fatigue took to recover after various maximal isometric contractions lasting 2 minutes.
Let us briefly go through each one of the studies.
A 2015 study by Kennedy et al. had subjects perform a maximum voluntary contraction of quadriceps for 2-minutes. Immediately after, there were minimal signs of central fatigue.
Another study by Kennedy et al. had subjects perform a 2-minute maximum voluntary contraction of the adductor pollicis (a muscle of the hand). Central fatigue had almost fully dissipated after 1 minute of rest.
A 2005 study Todd et al. had subjects perform a 2-minute maximum voluntary contraction for the elbow flexors. Central fatigue had dissipated within 30 seconds of completing the exercise.
Of course, these protocols are not identical to sets with typical weight training exercises. Most exercises are performed with a concentric and eccentric phase, while the mentioned studies involved maximal isometric contractions.
Moreover, all of these studies involved 2-minute contractions, most typical sets last far less than 2 minutes. This is an important point.
There seems to be a belief that heavier loads, and therefore shorter set durations, cause the most central fatigue. However, this is a misconception.
Lighter loads, and therefore longer duration sets, likely cause greater central fatigue.
A 2015 study by Zghal et al. had subjects perform an isometric contraction with their quadriceps for 33 straight minutes at 15% of their maximum voluntary isometric contraction strength. The authors noted that central fatigue dissipated within 3-9 minutes after this protocol.
A 2006 study by Sogaard et al. had subjects perform an isometric contraction with their elbow flexors for 43 straight minutes at 15% of their maximum voluntary isometric contraction. Central fatigue took roughly 20 minutes to disappear.
A 2007 study by Smith et al. had subjects perform an isometric contraction with their elbow flexors for 70 straight minutes at 5% of their maximum voluntary isometric contraction. 30 minutes later, central fatigue was still present. Unfortunately, they did not take any further measurements after these 30 minutes, so we do not know when central fatigue fully dissipated.
Therefore, given typical hypertrophy sets are generally shorter in duration than 2-minutes, the indirect evidence would suggest that central fatigue should disappear quicker than the values we saw for the various 2-minute isometric contractions. Potentially imply that central fatigue disappears after 30 seconds or less of typical hypertrophy sets, implying 30 seconds of rest should be all that’s needed.
But as we saw with the longitudinal research, this was not the case. Longer rest intervals (2.5 to 3 minutes) produced greater hypertrophy than shorter rest intervals (1 minute or less) with compound exercises. As a result, there seems to be a potential flaw with the central fatigue hypothesis.
I should note that all the research we have looked at assessing how long it takes for central fatigue to disappear used isometric contractions for only one muscle group, essentially meaning they could be classified as isolation exercises.
But remember, although there is some indirect evidence suggesting compound exercises could induce greater central fatigue than isolation exercises, the review paper by Weavil et al. suggests otherwise.
At the end of the day, to truly figure out if central fatigue could be the reason behind why longer rest intervals are superior with compound exercises, we would need research assessing how long central fatigue takes to disappear after various sets with compound exercises as well as isolation exercises.
Influence of Sex, Strength Level, and Age on Rest Intervals
Aside from distinguishing between compound and isolation exercises, it is often overlooked that sex, age, and even your current strength levels can play a role in determining the duration of rest intervals.
Most of the studies we have looked at so far had men as their subjects, though a few studies did have both men and women as their subjects. But, this clouds our ability to draw out any potential differences between men and women.
Intriguingly, there is some evidence that women may be able to recover quicker between sets compared to men.
A 2012 study by Ratamess et al. recruited 22 men and women with at least 1 year of training experience. The subjects performed 3 sets on the bench press with a 75% one-rep max load. On three separate occasions, they performed this protocol with either 1-minute, 2-minute, or 3-minutes of rest between sets.
The participants were encouraged to perform 10 reps per set.
Looking at the results, regardless of the rest interval used, women performed a higher number of reps over the three sets compared to the men, indicating they have a greater recovery ability. Other studies also have similar findings (one, two, three).
However, the authors noted that when they adjusted for bench press strength (using a statistical method), there was no difference in repetition performance between men and women over the three sets.
This would suggest that gender per se did not explain the faster recovery, rather it appears that your strength level impacts how quickly you recover.
In other words, the weaker you are on an exercise, the quicker your performance can recover. Conversely, the stronger you are, the longer it would take for your performance to recover.
In this study, the women’s average bench press one-rep max was 36kg, while the men’s average bench press one-rep max was 112kg.
Given the women were weaker than the men in this study, this seemed to explain why they were better able to sustain their repetitions from set to set.
To further test this idea, the researchers also had a second part of the study. They recruited 22 men and split them into a low one-rep max group or a high-one rep max group.
On average, the low one-rep max group’s bench press one-rep max was 81kg, while the high one-rep max group’s bench press one-rep max was 141kg.
Like the first part of the study, the subjects performed 3 sets on the bench press with a 75% one-rep max load. On three separate occasions, they performed this protocol with either 1-minute, 2-minute, or 3-minutes of rest between sets.
The participants were encouraged to perform 10 reps per set.
Looking at results, regardless of the rest interval used, the low one-rep max group were able to sustain their repetitions across the three sets better than the high one-rep max group.
Therefore, regardless of if you’re a man or woman, the weaker you are on an exercise, the faster you likely can recovery between sets of that exercise, and so your rest intervals need not be excessive here.
However, having said all of this, there is other evidence suggesting that when women and men are matched for strength, women are still able to recover faster.
A 1999 study by Fulco et al. matched 9 men and 9 women for strength of their adductor pollis (a muscle of the hand). The researchers had subjects perform a fatiguing isometric contraction of their adductor pollis. One-minute after this, the women had recovered to 71% of their baseline strength, while the men only recovered to 65% of their baseline strength.
As strength levels were matched between the men and women, it appears women did truly recover quicker than men.
Research comparing various physiological and anatomical differences between men and women also lend support to the idea that women may intrinsically have the ability to recover quicker between sets.
Some evidence indicates that women have greater blood flow than men. Greater blood flow to the muscle would accelerate the recovery process between sets.
Additionally, some evidence suggests that women have a higher proportional area of type 1 muscle fibers compared to men. Type 1 fibers, often called slow-twitch muscle fibers, have faster recovery abilities, and are more fatigue resistant compared to type 2 fibers (fast-twitch fibers). Based on this, women would not only be able to recover quicker between sets, but each set would also generate less fatigue.
So, irrespective of whether the exercise is an isolation exercise or compound exercise, women can likely rest shorter than men would without any problem.
Although we could not conclude anything with isolation exercises, we did conclude that 2.5 to 3 minutes of rest between sets was superior to shorter durations with compound exercises. However, this conclusion was from studies that mainly involved men. Women might be able to get away with resting 1 to 2 minutes between sets of compound exercises.
All but one (Villanueva et al.) of the studies assessed so far have focused on young men and women.
Two studies suggest that elderly men and women might be able to recover faster between sets than younger men and women.
A 2008 study by Theou et al. recruited 20 young women (between 20 and 30 years old) and 16 elderly women (between 60 and 80 years old).
The researchers had these subjects perform 3 sets with an 8 rep-max load on an isokinetic dynamometer designed to provide knee extension and knee flexion resistance. On three different days, they performed this protocol with either 15 seconds, 30 seconds, or 60 seconds of rest between sets.
For both the young and elderly women, 60 seconds of rest resulted in the maintenance of knee extension torque throughout the 3 sets, while the 30 and 15 second rest intervals did not.
The young and old women were able to maintain knee flexor torque throughout the 3 sets with 60 seconds of rest between sets. But the elderly women were also able to maintain knee flexor torque throughout the 3 sets with 30 seconds of rest between sets.
This implies that 30 seconds of rest between sets was sufficient to recover knee flexion torque for the elderly, whereas the younger women required 60 seconds of rest between sets.
Therefore this study partially supports the idea that elderly women may be able to recovery quicker between sets compared to younger women.
Another study by Bottaro et al. recruited 17 young men (average age of 25 years old) and 20 elderly men (average age of 66 years old).
The subjects performed 3 sets of 10 reps on knee extensions with an isokinetic dynamometer. On two separate occasions, they performed this protocol with either 60 seconds or 120 seconds of rest between sets.
With both rest intervals, the young men experienced a greater decline in peak knee extension torque across the 3 sets compared to the elderly men. This implies that the elderly men had a quicker recovery between their sets.
In the two studies (Theou et al. and Bottaro et al.), the elderly subjects were weaker compared to the younger subjects. As discussed already, this strength difference likely would partly explain why the elderly may be able to recovery quicker between sets.
However, there is also evidence that with aging, there is a decrease in the size of type 2 muscle fibers and an increase in the proportion of type 1 fibers. As mentioned, type 1 fibers have quicker recovery abilities and are more fatigue resistant compared to type 2 fibers. Therefore, this would be another potential reason behind why the elderly may be able to recover quicker between sets compared to the young.
When we looked at the research on compound exercises and muscle growth, we did have one study by Villanueva et al. conducted on elderly men (their average age was 68 years old).
Increases in lean body mass were greater for the group resting 1 minute between sets compared to the group resting 4 minutes between sets. On the face of it, this would support the idea that the elderly can successfully use short rest intervals.
But recall volume load was equated between the two groups, meaning the 1-minute rest group would have been training closer to failure than the 4-minute rest group. Therefore, it’s unclear how this study would conclude if both groups took their sets to failure.
So more research would be required to truly get an idea of what rest intervals promote greater hypertrophy in the elderly.
Ultimately, from the acute research, the elderly can probably rest less between sets compared to the young.
With isolation exercises, the only sensible advice to give based on the current evidence would be to select a rest interval the elderly may find comfortable and practical.
For compound exercises, given the majority of the evidence implies that in young men, 2.5 to 3 minutes of rest between sets produces greater hypertrophy than shorter rest intervals, it could be assumed that the elderly may be able to achieve optimal muscle growth with a rest interval shorter than this. Perhaps 1 to 2 minutes of rest between sets of compound exercises would be sufficient.
Decreasing Rest Intervals Over time
There is some evidence that a person could over time, slowly decrease the duration of their rest intervals without compromising muscle hypertrophy.
A 2010 study by De Souza et al. split 20 men with at least 1 year of training experience into a constant rest group or a decreasing rest group.
Both groups trained 6 days per week for 8 weeks.
For the first two weeks, both groups trained identically. They performed all exercises for 3 sets with a 10-12 rep-max load and 2 minutes of rest between sets. Workout 1 and workout 2 were each performed three times per week.
From weeks 3-8, both groups performed each exercise for 4 sets with an 8-10 rep-max load, but their rest intervals differed. Their weekly workout schedule also changed (image below).
The constant rest group continued using 2 minutes of rest between sets.
The decreasing rest group, throughout these 6 weeks, gradually decreased the duration of their rest intervals weekly from 105 seconds of rest to 30 seconds of rest between sets.
After the 8 weeks, increases in thigh and arm cross-sectional area were similar between both groups.
Put differently, gradually decreasing your rest interval duration’s week to week appeared to not compromise muscle growth in comparison to a group consistently resting 2 minutes between sets.
Looking back at the exercises performed by both groups, they used a range of compound and isolation exercises. Returning again to our findings much earlier, the research is conflicting on whether long or short rest intervals are optimal with isolation exercises. But with compound exercises, 2.5 to 3 minutes of rest produced greater increases in muscle hypertrophy versus shorter rest intervals.
Based on this information, you could argue that the constant rest group in the De Souza et al. study were not resting optimally anyway, as they rested only 2 minutes between sets. Given 2.5 to 3 minutes of rest is preferred for compound exercises, we cannot truly conclude that gradually decreasing rest intervals does not compromise muscle growth.
At the same time though, it is important to consider that the conclusion 2.5 to 3 minutes of rest is preferred for compound exercises comes from research comparing this rest interval to duration’s of 1-minute or less.
It’s possible that when comparing 2.5 to 3 minutes of rest to 2 minutes of rest between sets with compound exercises, there would be no difference in muscle growth. But there is no research assessing this. Hopefully, future research looks at this.
So, although the preliminary evidence on the use of decreasing rest intervals is somewhat promising, more evidence is still most definitely required.
If you’ve made it all the way here, thank you! I hope this article was valuable. In two previous (much shorter!) articles, we’ve looked at the evidence on if flexing between sets or stretching between sets could improve muscle growth. So, feel free to check them out if you’re interested!