What Two Weeks of Being Lazy Does to Your Body

Laura Tedesco

Is couch surfing your summer activity of choice? You may be losing strength and muscle faster than you’ll be able to regain it. (Photo: Corbis/Amyn Nasser)

It’s the season of poolside piña coladas, lazy days, and vacations from the gym — which, as any swimsuit-wearing gal or chest-baring guy can attest, adds up to less-than-desirable results. How fast, exactly, will your muscle tone and strength deteriorate? That’s what researchers from the University of Copenhagen set out to determine in a new study, published in the Journal of Rehabilitation Medicine.

To assess the effects of being totally sedentary — as an athlete might be after an injury, for example — the scientists used knee braces to immobilize one leg of 17 young men (average age: 23) and 15 older men (average age: 68) for two weeks. The study participants were instructed to use crutches and avoid doing any weight-bearing activity with the out-of-commission leg. Before the study, after the immobilization, and after a six-week retraining period, the scientists tested the men’s body composition and strength in each leg.

Not surprisingly, the guys lost strength in the immobilized limb — specifically, the young men experienced a 28 per cent reduction in strength from baseline, while the older men showed a 23 per cent decline. For the younger guys, this is like aging 40 to 50 years in a matter of days, study author Andreas Vigelso tells Yahoo Health.

Of course, simply being sedentary — say, spending more time on the couch than moving around — isn’t the same as completely immobilizing one limb. But even the leg that the guys were able to use took a hit over the two-week study period: Both groups lost strength — about 10 per cent from baseline — in the leg that wasn’t put in a brace.

This loss may reflect what would happen to your legs if you were to take a couple weeks off from the gym, says Vigelso. “We measured the whole-body activity level of the participants, and it decreased by one-third during the immobilization, which may have caused the decline in strength” in the non-braced leg, he says.

In fact, if you’re still using both legs for daily living, but significantly decrease your activity level, you may actually lose more than 10 percent of your strength. “If one leg is immobilized, you tend to jump around on the other leg, which trains the leg and counteracts the loss,” explains Vigelso. But if you’re just being lazy, you’re not likely to hop around your house on one leg, meaning your muscle loss could be even more significant.

The decline in strength was accompanied by a decrease in lean mass — but only in the younger study participants: The 20-something guys lost about one pound of lean tissue in their immobilized leg.

Why did only the young guys shed lean mass? “The more muscle you have, the more you’ll lose,” says Vigelso. “Which means that if you’re fit and become injured, you’ll most likely lose more muscle mass than someone who is unfit over the same period of time.” What you can expect from a real-world exercise hiatus: If you reduce your daily number of steps from the recommended 10,000 steps per day to approximately 1,500 steps a day for two weeks, you’d lose about .55 pounds of lean mass per leg, estimates Vigelso.

And in the study, working out for six weeks — three times the duration of the immobilization period — wasn’t enough to restore the men’s losses. After the retraining period, which involved both steady-pace cycling and interval training, the study participants had regained some of their strength, but still hadn’t returned to their baseline levels, even though the younger men built back all of the lean mass they’d lost.

This finding left the researchers “puzzled,” says Vigelso. “We thought cycle training would be sufficient” to restore the men’s strength, since they had become so weak. “It’s possible that the intensive endurance training — three to four times a week — in untrained individuals may impair explosive leg strength,” he speculates. “It’s also well-known that cycling doesn’t improve strength very efficiently. And this may also be the case in even very weak people.” In other words, spin class may not be the place to start after a long stint out of the gym, although the training did help decrease the men’s total body fat.  

So why do people lose strength faster than they can regain it? “The short answer is it’s easier to break down than to build up,” Vigelso says. “We lose muscle mass, strength, and fitness if we are inactive to save energy — it’s an evolutionary mechanism. Your body has no reason to maintain muscle mass if it’s not needed.” That means the unused muscle quickly wastes away. By contrast, if you begin exercising, it takes much more time to make gains, because your body has to adapt to the new level of physical activity, he says.The ultimate fix is, of course, to avoid taking too much time off from the gym. But when you do take a break — whether because you’ve been injured or you’re on vacation — strength training is the ideal way to recover your losses, says Vigelso. Aerobic exercise can be added to your regimen, but shouldn’t be relied upon alone — even if done in explosive bursts — to help you rebuild lost strength and lean mass. And even if you hit the weights hard, “it is important to accept that it takes time to recover after an injury or short-term inactivity,” Vigelso says. Stick with it long enough, and your body will bounce back.