You may try to exercise most days, but what happens to your fitness level if you have to stop for a while, perhaps because you become ill or injured or because work, travel, or terrible weather prevents you?
How quickly it takes for detraining (also called deconditioning) to occur once you stop exercising depends not only on your age, how fit you are, and how long you have been exercising, but also on what type of exercise you were doing and at what level.
When you stop exercising, many physiological changes take place. You begin to lose the cardiovascular (aerobic) gains you made—notably your heart’s ability to pump blood more efficiently, your muscles’ improved capacity to process oxygen, and your body’s enhanced ability to use carbs for fuel. Training-induced improvements in blood pressure, blood cholesterol, and blood sugar levels start to disappear. And when you stop strength training, you slowly lose the gains you made in muscle fiber size and other neuromuscular training adaptations.
Even two weeks of detraining can lead to a significant decline in cardio fitness, according to the American College of Sports Medicine. Not exercising for two to eight months leads to loss of virtually all fitness gains. In general, the loss of aerobic capacity occurs more rapidly than declines in muscle strength.
Athletes and other people who have trained intensely and been fit for a long time experience more gradual declines when they stop working out compared to newer exercisers. For instance, studies have found that when well-trained runners, cyclists, or swimmers abstain from all exercise, they lose on average only a little more than half of their gains in aerobic conditioning in about three months. In contrast, when sedentary people undertake a two-month cycling or running regimen, most lose all their aerobic gains if they stop for two months.
But there are many variations in outcomes. In a Spanish study this year in the journal Nutrition, Metabolism and Cardiovascular Diseases, obese people (average age 52) with metabolic syndrome did aerobic interval training for four months, which led to improvements in aerobic capacity, HDL (“good”) cholesterol, blood pressure, waist circumference, and insulin sensitivity. Just one month of no exercise resulted in loss of most improvements, notably their aerobic gains and improved insulin sensitivity and HDL.
In a Portuguese study in the journal Gerontology in 2009, women over 65 who hadn’t exercised regularly undertook a fitness program for eight months that improved aerobic and muscular fitness as well as flexibility and balance. After three months of detraining, they lost most of their improvements in strength and flexibility; gains in aerobic fitness and balance were less affected by detraining.
Slowing the losses
After you have detrained, how long will it take you to regain your previous level of fitness when you start exercising again? It’s hard to predict. After a three-month hiatus, a week or two of training won’t return you to your peak condition. If your layoff was long and total, it may take you nearly as long to retrain as it did to become fit initially.
But people rarely are forced to completely stop exercising long term, unless they are very ill or injured. More often, they find they have less time to exercise because of work or other commitments and thus experience only partial detraining. The good news is that studies show that when people merely cut back on exercise for extended periods, they can minimize the effects of detraining.
If you’re forced to abandon your normal fitness routine for more than a couple of weeks, try to undertake an abridged workout schedule—even one session per week—rather than stopping altogether. If you don’t have time for a full workout, you can break it up into several shorter sessions. One option is to do two or three short sessions a week of high-intensity interval training—for instance, all-out one-minute sprints of running, cycling, stair climbing, or jumping rope alternating with one-minute rests (or minimal exertion) for a total of 10 minutes. Research shows that this can be a good way to maintain aerobic fitness.
If you have stopped exercising because of an injury, such as a broken bone or ruptured tendon, you can slow the detraining effect by working unaffected muscle groups, such as exercising the opposite arm or leg.