We know that “mechanical unloading,” a fancy term for sitting around on your butt, reduces the number of satellite cells. Muscle size is determined by the number and size of these satellite cells.
But there isn’t much known about how quickly gym rats lose muscle when they’re not exposed to regular resistance training. The only directly relatable research measured the effects of a paltry two-week layoff.
The lifters in this study that continued to ingest their usual amount of protein didn’t lose a damn thing as far as strength and size (not so for the guys who didn’t maintain their protein habits). That’s great, but not much is known about layoff periods longer than two weeks.
There is, however, plenty of research on strength and muscle loss that occurs with complete muscle disuse, like when you go skiing in Aspen and fall off a mountain.
In cases like that, there appears to be an initial 14-day “cushion” where laid-up patients can keep most of their muscle mass and strength, but after that, it diminishes rapidly.
On average, patients lose about 0.5% of their lean body mass and about 1.5% of their strength per day (after that 14-day cushion), obviously topping out at some point. But again, that’s in bedridden patients, not healthy lifters who just didn’t have access to a gym.
Luckily, we do have plenty of anecdotal and experiential evidence that tells us the loss of muscle and strength from a lay-off isn’t nearly that bad.
The average lifter will probably lose between 6 and 10 pounds of muscle mass during a three-month period. Remember, though, that we’re talking about a three-month period of living like a normal non-lifter who doesn’t do any real physical work outside of taking out the trash.
Losing any amount of muscle mass can be emotionally deflating, though, but here’s where some of those studies on muscle loss in bedridden people come in handy. They provide us with some nutritional strategies that should mitigate muscle and strength loss in the healthy-but-gymless.