Breaks in resistance training do not impair long-term development in strength and muscle size

The study compared the results of 20 weeks of resistance training in two groups, one with continuous training and one with a 10-week break midway.

The study found that the results for maximum strength and muscle size development were similar in both groups. According to the researchers, the equal progress in both groups was due to the fact that maximum strength and especially muscle size quickly returned to pre-break levels when training was resumed.

"During the first few weeks after the break, progress was very rapid and after only five weeks of re-training, the pre-break level had already been reached," says Eeli Halonen from the Faculty of Sport and Health Sciences, who is writing his doctoral thesis on the effects of the training break.

"For the group training continuously for 20 weeks, progress clearly slowed after the first ten weeks," Halonen adds. "This meant that there was ultimately no difference in muscle size or strength development between the groups."

"Muscle memory" will next be studied at the cellular and molecular level

The phenomenon where the previous level of muscle size is quickly regained after a break is termed "muscle memory."

"The physiological mechanisms of muscle memory are not yet fully understood," say senior researchers Juha Hulmi and Juha Ahtiainen, "and our next step is to study in more depth the cellular and molecular changes in muscles that could potentially explain this phenomenon."

Maximum strength is better preserved than muscle size

The study also found that maximum strength was better preserved during the break than muscle size.

"This could be explained by the fact that changes in the nervous system may be more permanent than peripheral changes in the muscles," Halonen says.

Based on this study and previous evidence, it seems that gym-goers have little to worry about occasional training breaks of up to ten weeks if the training is otherwise regular and progressive during the rest of the year.

It is worth bearing in mind, however, that in this study those who took a break from training achieved the same result in 30 weeks as those who trained continuously for 20 weeks.

"Of course, the break slows progress some," Halonen points out, "but it is comforting to know that it is possible to reach the pre-break level surprisingly quickly."

The study was conducted at the Faculty of Sport and Health Sciences at the University of Jyväskylä. The participants were young Finnish men and women who were physically active but had no previous experience of systematic resistance training.

The results of the study have been published in the Scandinavian Journal of Medicine & Science in Sports. The study was funded by the Rehabilitation Foundation Peurunka, the Finnish Sports Research Foundation, the Academy of Finland, and the Faculty of Sport and Health Sciences at the University of Jyväskylä.