Why This Should Matter To You: Many people have made claims that rest periods have to be short for growth. However, this information clearly shows us that having “adequate” rest is probably far more important for growth than any potentially side effects of shorter rest periods. It matters because it provides really important information about optimizing your training. This study showed almost double the growth with just a 2-minute increase of rest between sets. I’ll let you figure out why this is important.
Purpose Of The Study
The purpose of the study in question was to evaluate differing responses to resistance training when rest periods are only 1 minute long (SHORT), compared to 3 minutes (LONG).
Essentially, there is this school of thought that rest periods should be kept to a minimum for a number of different reasons. First would be a large increase of metabolic stress (the pump). Since the time frame of clearing metabolites is short, it’s often not ample enough, leading to a build up.
Second, it’s thought that muscle fatigue is a driver of hypertrophy and thus if fatigue increases as a result of short rest periods, this may hypothetically advantageous.
Essentially, this group of scientists wanted to observe whether or not shorter rest periods are actually advantageous for growth or if it’s a better idea to rest longer.
23 male volunteers were recruited for this study and were considered to be resistance trained. Only 21 finished due to non-compliance.
Once accepted into the study, subjects were placed into 1 of 2 groups, groups being according to rest length. The SHORT group completed resistance training with 1-minute rest while LONG completed resistance training with 3 minutes of rest.
All participants took part in the same resistance training protocol. The only manipulation was the rest period duration.
For a period of 8 weeks, subjects participated in resistance training 3 times per week, using a full body, bodybuilding routine consisting of 7 exercises including:
Sets were performed 8-12 repetitions per sets, for 3 sets per exercise, taken to failure.
It’s important to note that having a range of reps here is appropriate. Theoretically, the longer rest periods should allow for higher amounts of repetitions (volume), which may be advantageous for growth.
Additionally, measurements of growth were obtained. First, ultra sound was used at the beginning of the study and at the end, to observe changes in muscle thickness. Additionally, tests for muscle strength and muscle endurance were taken. Lastly, total volume load was calculated to allow us to observe the difference in volume afforded by each rest period and then compare that to the findings.
Total volume load was significantly greater for the LONG rest group compared to the SHORT rest group (51,385 ± 9420 vs. 44,755 ± 12,166 kg, respectively).
The LONG rest group increased elbow flexor muscle thickness by 5.4% compared to only 2.8% (non-significant) in the short duration group. LONG rest wins here.
LONG group increased Triceps Brachii thickness by 7.0% compared to only 0.5% in the SHORT rest group.
Both groups observed significant increases over that of baseline, but only LONG was significantly different from SHORT. In fact, the increase for LONG was about double that of SHORT. 13.3% increase for long compared to 6.9% for SHORT. Both were significantly increased from baseline. LONG was significantly greater at post than pre training AND that of the change for SHORT.
Both groups observed significant increases of muscle thickness for the Vastus Lateralis (outside quadriceps muscle) compared to baseline. 11.5% increase for LONG cared to 10% increase for SHORT.
Bottom line: Almost every measurement for muscle thickness favored LONG duration rest periods. In some cases, the advantages were almost double in favor of LONG rest.
1 RM Squat
There were significantly greater increases in 1 RM squat strength for LONG compared to short. While both showed significant improvements, the LONG group displayed a 15.2% increase of strength compared to only 7.6% increase for the SHORT group.
1 RM Bench
Only the LONG group displayed a significant increase of 12.7% compared to only 4.1% observed for the SHORT duration rest group.
Bottom line: LONG duration rest periods were favored all around for improvements of strength.
Both groups displayed a significant improvement in Muscle endurance performance (50% of 1 RM to failure). LONG displayed a 23.2% increase where SHORT displayed a 13.0 % increase. As you can see, LONG displayed almost a double increase over that of SHORT, despite them both being significant improvements from baseline.
Overall, based on these findings, it seems fairly straight forward that LONG rest periods of around 3 minutes are superior compared to much shorter duration rest periods, with the specific goal of increasing hypertrophy, strength and endurance.
Keep in mind that while this study showed pretty much conclusively that longer rest periods are beneficial for growth, shorter rest periods still have their place. If your goal is fat loss, moving your anaerobic threshold or if you want a high level of fitness (think crossfit) then shorter rest periods will provide their own benefit.
However, if your goal is increasing muscle thickness and strength, rest periods should be taken advantage of. Clearly the benefits of resting a bit longer outweigh the theoretical and unproven benefit of shorter rest periods, specifically in terms of muscle growth, strength and strength endurance.
I suggest for most workouts, keeping rest periods for larger compound movements around 3 minutes with isolation movements curtailed back to around 2 minutes. Isolation movements typically require a bit less rest than larger movements. Plus, having 3 minute rest periods between every set may become quite time consuming if you have many exercises to do.
Just keep in mind that longer rest periods are probably more advantageous if your goals are increasing strength and muscle size.
The Results Aren’t Surprising
Really, the findings aren’t surprising at all. If you’re to consider that above all else, total volume increases are probably the number on driver of growth, then it makes sense that we saw the differences we did in this study.
Having a longer duration of rest allows for the muscle to recover and metabolites to be cleared from the muscle, allowing for a higher ability to contract and to contract for a longer period of time than compared to much shorter durations of rest.
Having longer rest periods means more recovery and more ability once you end up actually doing the set. I mean, is it surprising that 3 minutes of rest would allow you to recover to a greater extent than only 1 minute? Not to mention, is it then surprising that longer durations would mean greater effort put forth during each set?
Personally, it’s not surprising at all. If volume is a major determinant of muscle growth, it makes sense that if longer rest periods allow you to increase that amount, then it should theoretically lead to greater gains.
There Was A Clear Winner
Rather than continuing to regurgitate what I’ve already said, let me say it one last time. Overall, LONG rest was superior and in fact, many of the measurements showed almost double the growth of the SHORT duration group.
Granted, SHORT rest periods may be advantageous for a number of different scenarios such as fatigue resistance, anaerobic threshold (repeated sprint ability), fat loss, metabolic conditioning, etc. So, shorter rest periods can’t be discounted.
But if the goal is increasing strength and muscle growth, we have to consider the most important aspects. For me, that’s ensuring that neural drive recovers (strength) and fiber recovery and metabolite clearance on the muscle growth side.
Having longer duration rest periods allows you to maximize both of those aspects. Sure, metabolic stress or the pump might be important but if your sets are intense enough, maintaining a pump after only 3 minutes of rest probably won’t be an issue.
Overall, LONGer rest periods won in just about every scenario.
Why This Should Matter To You
Many people have made claims that rest periods have to be short for growth. However, this information clearly shows us that having “adequate” rest is probably far more important for growth than any potentially side effects of shorter rest periods. It matters because it provides really important information about optimizing your training. This study showed almost double the growth with just a 2-minute increase of rest between sets. I’ll let you figure out why this is important.
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