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Rest periods of 2 or 5 minutes between sets? It makes no difference to muscle growth

You've been working hard for weeks and you're shattered when it comes to the evening. You really want to continue training but you notice that you need longer rest periods between sets. According to Finnish sports scientists, that's no problem. A study, which they published in 2005 in the Journal of Strength and Conditioning Research, shows that your progression will be the same whether you take a 5-minute or 2-minute break.

Strength training manuals advise short rest breaks between sets. Two minutes' rest is the maximum that the average trainer is likely to allow you. The researchers questioned how well founded this guideline actually is. So they did an experiment with a dozen men who'd all been doing weight training for an average of 6 years.

Half of the subjects first trained for three months taking 2-minute rests [SR]; the other half took 5-minute rests [LR]. When the three months were up the groups changed over: the group that had first taken 2-minute rests now took 5-minute breaks and vice versa.

The men trained 4 times a week and did sets of 8-12 reps. And once a week they trained their long leg muscles by doing squats, leg-press and leg extensions. The researchers focused on the results of the leg training. The figure below shows that the circumference of the quadriceps femoris muscle increased by the same amount in the SR and the LR training [right]. The researchers used MRI scans for the measurements. The same is true of the weight at which the subjects could manage just 1 rep on the leg-extension machine [left].

Rest periods of 2 or 5 minutes between sets? It makes no difference to muscle growth Rest periods of 2 or 5 minutes between sets? It makes no difference to muscle growth

Rest periods of 2 or 5 minutes between sets? It makes no difference to muscle growth
However, the maximal isometric force that the subjects managed to develop on the leg-extension machine increased more in the training period with the longer rests. See the figure on the right.

The researchers detected no differences in hormonal response to strength training with 2-minute and 5-minute rests. They do note, however, that the athletes who took shorter rests produced slightly more growth hormone.

"The length of the rest periods between the sets may not be a crucial factor in hypertrophic types of training protocols as long as muscles are overloaded with several sets to the concentric failure", the Finns conclude. "Large exercise stimulus could be attained either with multiple training sets with short rest periods between the sets or with somewhat fewer sets with longer recovery period between the sets but with somewhat higher intensity."

Athletes who are aiming for pure strength on the other hand are better off training with longer rest periods. That's the cautious conclusion that the researchers draw from the positive effect of the LR training on the maximal isometric force. "LR training may create more optimal training stimuli for maximal strength development than SR training", write the Finns.

J Strength Cond Res. 2005 Aug; 19(3): 572-82.

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