|Resting long enough to maximize your training volume could be the key to success, i.e. strength and size gains.|
Of these, the former is pretty much uncontested. The latter, however, is still questioned by a camp of inconvincible skep- tics, who simply ignore the fact that there's ample evidence that "[h]igher-volume, multiple-set protocols have consistent- ly proven superior over single set protocols with respect to increased muscle hypertrophy" (Schoenfeld. 2010).
What still isn't clear, though, is the role of other training parameters, such as the time you take to recover between multiple sets and exercises aka the "rest intervals". As Schoenfeld et al. point out in the introduction to their most recent study, "several studies have investigated the effects of varying rest interval length on muscular adaptations," (Schoenfeld. 2015) albeit with contradictory results: While Ahtiainen et al (2005) were unable to find a significant inter-group size or strength difference in well-trained subjects (6.6 +/- 2.8 years of continuous strength training) who rested 2 minutes compared to those who rested only 5 minute in response to their 21-week training intervention, Buresh et al (2005) reported more recently that significantly greater size increases of the arms and a trend for greater muscle hypertrophy in the legs in young, albeit untrained subjects who rested for 2.5 minutes instead of just one.
longer rest periods compromise the gains of older trainees", I've discussed last year, already. What about the lack of different increases in strength endurance? I have to admit that I do not discuss this finding of the study in detail. While one would expect that shorter rest intervals would produce greater strength endurance adaptations, the researchers observed the opposite, an - albeit non-significantly larger increase in strength endurance in the 3-minute-rest group that correlated with the increase in 1RM strength. Further studies will have to show what the underlying mechanism of this counter-intuitive observation is and whether it may be muscle specific, i.e. occur only in the upper, but not in the lower body.