Every month, Chris and I write the monthly S&C Research review service. Subscribe, and you will learn about the 50 most important sports science studies published every month, covering strength & conditioning, biomechanics, anatomy & physiology, and sports medicine.
In this article, Chris has written a short preview of the September edition, which covers some fascinating new research into rest period duration.
Does rest period duration affect gains in strength during pre-exhaustion training?
The study: The effects of pre-exhaustion, exercise order, and rest intervals in a full-body resistance training intervention, by Fisher, Carlson, Steele, and Smith, in Applied Physiology: Nutrition and Metabolism, 2014 In, this study, my friend James Fisher led a team of researchers to investigate the effects of pre-exhaustion training, which has probably never been studied in a long-term trial before. Although this study is getting a lot of press already for its exploration of pre-exhaustion training, it might escape some people that the researchers actually also looked at rest period duration as well. There were 3 training groups: (1) pre-exhaustion training (single-joint exercises prior to multi-joint exercises) with as little rest as possible, (2) pre-exhaustion training (single-joint exercises prior to multi-joint exercises) with 60-second rest periods, (3) the same exercises in the reverse order (multi-joint exercises prior to single-joint exercises) with 60-second rest periods. By comparing the first two groups, we can see the long-term effects on strength gains of very short and short-to-moderate (60 seconds) inter-set rest period duration. In fact, there was no difference in strength gains in respect of the gains in any of the exercises. Whether different results would have been observed if another group had used an even-longer rest period, however, is unclear.
Practical implication: rest periods don’t make that much difference to strength gains during pre-exhaustion training, so when using this method choosing a length of time for resting between sets can be made based on practical issues, such as length of overall workout, intended volume of training, working in with a training partner, etc.
Does rest period duration affect gains in size?
The study: The effect of inter-set rest intervals on resistance exercise-induced muscle hypertrophy, by Henselmans and Schoenfeld, in Sports Medicine, 2014 In this review, the researchers assessed the effect of rest period duration during resistance-training for hypertrophy. The reviewers explain that although many previous authors have recommended short rest intervals of 30 – 60 seconds for achieving the greatest gains in muscular size, these recommendations are not supported by the findings of the limited number of long-term trials, which show either no effect or a benefit of longer rest period durations. Interestingly, the reviewers raise an important concern relating to short rest periods. If short rest periods are not directly beneficial, then whether they are used is largely a matter of personal preference or workout duration, unless they have any adverse effects. In fact, the reviewers did note some safety concerns. Previous studies have found that when using very short rest period durations, neuromuscular postural control and proprioception are negatively impacted by fatigue. Thus, short rest period durations are a higher-risk strategy, particularly when using multi-joint, free-weight exercises with heavy loads. So the use of short rest periods does not seem to have a good risk-reward ratio where the primary goal is hypertrophy. Whether the same adverse effects would be observed in machine-based workouts, however, is unclear.
Practical implication: rest periods don’t make that much difference to gains in muscular size so for bodybuilders and physique athletes, choosing a length of time for resting between sets can be made based on practical issues, such as relative safety, length of overall workout, intended volume of training, working in with a training partner, etc.
Do 1-minute or 2-minute rest periods lead to significantly different training volumes?
The study: Comparison of repetition number between uni-joint and multi-joint exercises with 1-min and 2-min rest intervals, by Dias, De Matos, Filho, Moreira, Hickner, Cardozo, Alves, Reis, and Aidar, in Journal of Exercise Physiology Online, 2014 In this study, the researchers assessed whether rest period duration would affect the number of repetitions performed in an acute resistance-training intervention using both single and multi-joint exercises in resistance-trained males. Unsurprisingly, they found that work done was significantly greater for the 2-minute rest period duration condition in comparison with the 1-minute rest period duration condition for both the single and multi-joint exercises. The researchers also noted some other important findings. They observed that neither the 1-minute nor the 2-minute rest period durations were sufficient for full recovery between sets, and they found that single- and multi-joint exercises display different training workloads with the same relative load with the same rest period durations. Specifically, they noted that the multi-joint exercises displayed larger reductions in the number of repetitions performed during repeated sets with shorter rest periods. Therefore, longer rest periods may be required for multi-joint exercises than for single-joint exercises in order for the same workload to be performed.
Practical implication: rest periods may need to be longer for multi-joint exercises than for single-joint exercises, in order to maintain high training volume. This may suggest that advanced bodybuilders may gain from using machines in their training, as it could allow them to perform more work in less time.
How do these studies affect our programming of rest periods?
These three studies contain important practical implications for programming rest periods during resistance-training, as follows:
- Pre-exhaustion training doesn’t benefit from extremely short rests;
- Rest period duration doesn’t make much difference to hypertrophy;
- More rest is needed for multi-joint exercises than for single-joint exercises.
These study results go to show that there is more to setting a rest period than long rest periods for strength and shorter rest periods for hypertrophy. Simple is usually better than overly complex but sometimes things just are that little bit more complex than we might want them to be.
Although complexity can be a distraction when writing programs, it certainly keeps the results of new studies interesting. Bret and I like to think we know sports science pretty well, so for fun, we’ll often guess an outcome before we read a study. We base our guesses on what other researchers have found and what know about the underlying mechanisms. But since the human body is so highly complex and unpredictable, we often guess wrong!