For many reasons, bodybuilders and others involved in weight training might have to take a break from the gym.
However, new Finnish research finds that even weeks-long interruptions in training won't hamper muscle-building efforts.
“Of course, the break slows progress some, but it is comforting to know that it is possible to reach the pre-break level surprisingly quickly,” said study lead author Eeli Halonen. He's a doctoral student in sport and health sciences at the University of Jyväskylä.
Halonen and his colleagues published their findings recently in the Scandinavian Journal of Medicine and Science in Sports.
In the new study, 42 adults (just over half were males) took part in one of two 20-week weight-training regimens.
In one group, folks engaged in weight-training sessions (exercises included leg presses and biceps curls) for the whole 20 weeks without interruption.
The second group exercised for 10 weeks, then took a 10-week break, then resumed exercise for another 10 weeks.
"Results for maximum strength and muscle size development were similar in both groups," the researchers concluded in a university news release.
For the 20 people that took the 10-week break midway, all measures of muscle improvement bounced back quickly, Halonen's group said.
“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,” Halonen noted.
That's probably due to a phenomenon known as "muscle memory," he said.
Meanwhile, “for the group training continuously for 20 weeks, progress clearly slowed after the first ten weeks,” Halonen said. “This meant that there was ultimately no difference in muscle size or strength development between the groups.”
What exactly is muscle memory?
“The physiological mechanisms of muscle memory are not yet fully understood,” said senior study authors Juha Hulmi and Juha Ahtiainen. They are a professor and an associate professor of sport and health sciences, respectively, at the university.
They added that "our next step is to study in more depth the cellular and molecular changes in muscles that could potentially explain this phenomenon.”