What Happens When You Stop Exercising?

Your body may show the signs of deterioration in a week, and more seriously after three.

You were regularly working out — building both aerobic capacity and muscle strength. But then you got injured and it’s taking weeks to recover. Maybe you got a flu and fell out of the habit of exercising. Maybe you’re in a rough spell of work and can’t make it to the gym — and you don’t know how long that will last. Maybe you did a new budget, dropped a gym membership, and haven’t figured out ways to exercise on your own.

Your regular activity also improved your coordination, stability and flexibility, and sugar and fat levels, says Harry Pino, PhD, a senior exercise physiologist at the Sports Performance Center at New York University’s Langone Medical Center.

When that activity comes to a halt, your body suffers. Exercise physiologists might refer to you as “apparently healthy but deconditioned.” The fitter you were, the faster you’ll lose stamina, strength, and coordination, though you’ll still end up ahead of someone who never exercised at all. After 10 to 28 days of sedentary living, anyone who works out regularly will see noticeable changes.

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Highly trained athletes tend to show a drop of aerobic endurance within three weeks of detraining, but even after 12 weeks they will still retain a significant amount of bulk strength and endurance. They can expect a rise in sugar levels and blood pressure.

For example, a man who can run 5 kilometers in 20 minutes will usually need about 24 minutes if he hasn’t been running for a month or two, Pino calculates.

This can be discouraging, and it doesn’t help that it will take longer to recover your capacity to exercise than it did to lose fitness.

What about muscle mass? After getting great results weight training for the first time, it’s easy to worry about losing those hard-won abs and pecs. A week away, say while on vacation or finishing a big project, won’t hurt. Worry more when a break lasts for months. In one study, people ages 20 to 30 lost from 6 to 10 percent of their strength in a knee exercise when they stopped training for 31 weeks, with most of the loss coming after the first three months.

Women, by the way, did just as well as men both in building strength and maintaining it.

Dropping out of a muscle-building program for a stretch of time is more of a problem at older ages. A group of 65 to 75 year olds lost almost twice as much strength as the younger set in the same study.

That’s because muscle mass, and the ability to create and maintain it, declines with age. After age 50, people who don’t exercise lose up to 0.4 pounds a year in muscle. Although there’s debate about how long athletes can keep up their performance, sadly, it looks like even contestants in the Senior Olympics gradually do worse in track and field events as they age.

Some people worry that their “muscles will turn into fat.” Actually, muscles atrophy and fat cells expand, so you look and feel bloated and round compared to your fit physique. You’re likely to gain weight, and many people feel a decline in mood and self-confidence. You may feel more stressed out by smaller problems because you haven’t been training your body to handle challenges.

At any age, strength is kind of a big deal. Muscles aren’t just for moving furniture. Evidence shows that being stronger, not just thinner, helps decrease the risk of diabetes, for example. Also, contrary to the image of dumb Popeyes, strength is linked to less risk of memory decline and Alzheimer’s disease.

Use it or lose it definitely applies to muscles, but the loss isn’t necessarily permanent. Strength exercises still work for anyone after time off. So does aerobic exercise.

During your off period, look for exercise you still can do. Try biking if you can’t run because of a knee problem. Can’t get to the gym? Lift soup cans at home and do squats and push-ups. While traveling, look for opportunities to walk rather than take taxis. Then get back into a routine, without pushing yourself so hard you get injured.