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Rest Intervals & Training - Part 2

Welcome to Part 2 of this exciting series looking at rest intervals and their effect on performance and muscular adaptations. Before we begin this article, let’s refresh our memories about what we concluded in Part 1:

  • At least 3 minutes rest appears to help with endurance levels and the ability to sustain repetitions in well trained men.
  • 3-5 minutes is required for recreationally trained men to perform subsequent sets of an exercise, however decreased repetitions seem almost inevitable.
  • Lower limb compound exercises require less rest time in between sets than upper body compound exercises to recover.
  • To maintain endurance training capacity (15 or more sets), it might be useful to lower the weights rather than take longer rest intervals. (Note: Lowering the weight to achieve whole sets may not be beneficial in achieving muscle growth as it is the load which will affect recruitment of muscle fibres and to initiate muscle damage of those muscle fibres)
  • Regarding tests of maximal strength, 1 minute is sufficient for recovery, but more may be required to ensure better safety.
  • In terms of power, 3-5 minutes is required to recover power by recovering muscle phosphocreatine stores.

Now, let's have a look at how different rest intervals affect our hormonal profiles and long term adaptations.

Biochemistry & Rest Intervals

For muscle adaptations, we need sufficient muscle damage and also repair mechanisms. We also need adequate nutrients and coordination of hormones and other compounds in our body to elicit these adaptations. Following from that, Kraemer et al1 tested the hormonal profile with different rest intervals in between sets. What was found was that 1 minute rest intervals led to increases in growth hormone release post workout, moreso than longer rest periods (3mins). However, cortisol levels were also increased which negate many of the positive effects of the growth hormone. The study was also unable to follow up the increases in growth hormone and the impact it had on muscle growth over time. Similar results were seen with Botaro et al2, however conflicting results by Ahtiainen et al3 showed that there was no difference between 2-5 minute rest periods on hormonal response or muscular adaptations.

Chronic Adaptations

While it's beneficial that rest intervals can affect our performance and our hormonal profiles, do these changes equate to long term modifications? A couple of studies have looked at different rest intervals in between sets and their effect on long term workout performance. Pincivero et al4 looked at power performance with 40 seconds vs. 160 seconds of rest between sets. Over 4 weeks, the longer rest interval group had significantly better increases in all measures of power than the shorter rest group. Robinson et al5 looked at strength and power in terms of squat strength and vertical jump with rest periods of 3 mins, 90 and 30 seconds. While vertical jump power was not different between groups, squat strength was increased with a longer rest interval. In a similar study, Willardson and Burkett6 compared 2 vs. 4 minute rest intervals and found that both groups were able to increase their squat strength, and in fact there was no considerable difference between those two groups. In terms of workout capacity however, the 4 minute group were able to perform better in more intense workouts. Other studies have looked at rest intervals on chronic adaptations to endurance capacity. Ratamess et al7 tested 5 different rest intervals (30 secs, 1, 2, 3 and 5 minutes) on endurance capacity and found that longer rest intervals resulted in the ability to complete whole subsequent sets. That is, the longer the rest interval, the more completed sets you were able to do. On the other hand however, Garcia-Lopez et al8 showed no appreciable increase in endurance capacity between 1 and 4 minute rest intervals.

Applying Rest Intervals to Training

So let’s review quickly all the research we’ve just looked at:

  • Rest intervals of 1 minute appear to be able to cause a rise in growth hormone release post workout however, not all studies have been able to show this.
  • There is no conclusive evidence as to whether the rises in growth hormone with changes in rest intervals lead to muscle growth changes.
  • Longer intervals of between 2-4 minutes may be able to help augment long term power and strength performance.
  • In early days of training, 4 minutes may be necessary to avoid fatigue to ensure sufficient volume to elicit chronic adaptations. However, with longer term training, the body seems to adapt and 2 minutes is able to produce enough volume to achieve similar chronic adaptations.
  • There is inconclusive evidence regarding rest intervals and its effect on long term muscular endurance, but some studies have shown the longer the rest interval, the better your ability to complete endurance sets (15 or more reps)

With that in mind, the American College of Sports Medicine has also set out rest intervals in relation to strength, endurance and general progression of resistance training. Quoting their 2009 recommendations9:

  • 1-2 mins rest intervals for general progression of muscular adaptations.
  • 3-5 mins rest intervals for progression in power performance.
  • <90 secs rest intervals for progression in endurance performance.

Rest Intervals - The Verdict

In this author’s opinion, it is still too early to tell whether or not changes in rest intervals will definitely affect muscle and performance adaptations, but it is definitely a factor to consider during your workouts. Adequate rest in between sets will help you prepare for following sets and to ensure you achieve a good workout. This author also believes it is important to individualise your rest intervals depending on the results you want. Keep in mind though that many factors affect results, so always have a global view when working out.

1 Kraemer WJ, Marchitelli L, Gordon SE, et al. 'Hormonal and growth factor responses to heavy resistance exercise protocols.' J Appl Physiol 1990; 69: 1442-50
2 Bottaro M, Martins B, Gentil P, et al. 'Effects of rest duration between sets of resistance training on acute hormonal responses in trained women.' J Sci Med Sport 2009; 12: 73-8
3 Ahtiainen JP, Pakarinen A, Alen M, et al. 'Short vs long rest period between the sets in hypertrophic resistance training: influence on muscle strength, size, and hormonal adaptations in trained men.' J Strength Cond Res 2005; 19: 572-82
4 Pincivero DM, Lephart SM, Karunakara RG. 'Effects of rest interval on isokinetic strength and functional performance after short-term high intensity training.' Br J Sports Med 1997; 31: 229-34
5 Robinson JM, Stone MH, Johnson RL, et al. 'Effects of different weight training exercise/rest intervals on strength, power, and high intensity exercise endurance.' J Strength Cond Res 1995; 9: 216-21
6 Willardson JM, Burkett LN. 'The effect of different rest intervals between sets on volume components and strength gains.' J Strength Cond Res 2008; 22: 146-52
7 Ratamess NA, Falvo MJ, Mangine GT, et al. 'The effect rest interval length on metabolic responses to the bench press exercise.' Eur J Appl Physiol 2007; 100: 1-17
8 Garcia-Lopez D, De Paz JA, Moneo E, et al. 'Effects of short vs long rest period between sets on elbow-flexor muscular endurance during resistance training to failure.' J Strength Cond Res 2007; 21: 1320-4
9 American College of Sports Medicine. 'American College of Sports Medicine position stand. Progression models in resistance training for healthy adults.' Med Sci Sports Exerc. 2009 Mar;41(3):687-708.
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