Rest intervals, which represent the recovery time allowed between sets, are generally divided into three categories: short (30 seconds or less); moderate (between 60 and 90 seconds) and long (3 minutes or more).
Depending on the length of these intervals, the impact on physical qualities (strength, endurance, power and speed) as well as on metabolite production will be different. It therefore seems obvious that their choice can have a non-negligible strategic importance on muscle hypertrophy(1).
Hypertrophy: choosing the right rest intervals
Considering the hypertrophic response, short intervals produce high metabolic stress (2), but the limited recovery time will cause strength capabilities to drop in subsequent sets; the benefit of high metabolic stress will therefore be greatly mitigated by a limitation in muscle strength (3).
On the other hand, long intervals that generate full (or near full) recovery make it easier to reproduce identical efforts, but although the mechanical strain is higher (due to better preservation of strength capacity), this advantage is also mitigated by much lower metabolic stress.
In both cases, short intervals are more effective than long intervals.
In both cases, short or long intervals, the advantages are strongly
altered by the disadvantages and therefore the moderate rest intervals
are the ones that seem to provide a quite satisfactory compromise
solution, at least as far as muscle hypertrophy is concerned.
The various studies on the subject have shown that it is during the first minute of recovery that most of the strength capacity is recovered (4). The main advantages are to create the necessary conditions of hypoxia which will favour a higher production of metabolites likely to stimulate hypertrophy.
But all the advantages, as shown in a study comparing the differences between recovery times of 1 minute and 2. 5 minutes (5), are diluted over time.
Indeed, as might be expected, it is the shorter times (1 minute) that cause a much greater rise in GH levels, but this rise diminishes sharply after the fifth week and becomes virtually zero after 10 weeks. This clearly indicates that training planning, i. e. varying the different parameters (including recovery times) during the sequence of cycles, is the only solution for those who want to make regular and optimal progress.
