Fitness IQ: How Long Does It Take to Lose Fitness?   

Sometimes things come up — Yom Tov, an injury, vacation — and you have no choice but to break routine and skip your regular fitness sessions. Once you pause, what happens to all those hard-won fitness milestones you earned with your regular exercise schedule? How long does it take your body to lose fitness?

Cardio Change

The loss of fitness — or detraining — happens over time. Cardiovascular fitness is affected first. Within the first two weeks of detraining, blood volume decreases. The heart pumps less blood throughout the body, which means less oxygen is available to muscles and cells, causing breathlessness. For endurance athletes, the change is even more drastic. Researchers noticed their cardiac structure changed, and the ventricular wall thickened. If you return to exercise after a two-week break, you may feel winded more quickly, and notice an overall diminished aerobic ability.

Endurance

Next hit is endurance, your body’s ability to maintain an exercise for a period of time. A regular fitness schedule promotes cell health by renewing mitochondrial production. But after three weeks, mitochondrial output begins to drop, and the body’s lactate threshold lowers, causing you to feel fatigued faster. If you restart exercise at this point, you may find you tire more easily. After eight weeks of detraining, muscle mass decreases, as does the maximum amount you’re able to lift. It takes longer to lose strength than aerobic fitness, though other factors contribute to the rate of loss. Level of fitness is a contributing factor. Athletes seem to lose strength at a slower pace. A 2020 study found that male athletes didn’t lose muscle thickness, strength, or performance in sports after three weeks of detraining.

Take a Break

Much of this scientific research was conducted using groups where there was a complete cessation of activity. If you need to take a break from exercise, for whatever reason, you likely won’t be completely sedentary. And even while on these breaks, there are ways to maintain fitness so that you won’t lose all your hard-won gains.

One way is to keep moving throughout the day. Take a short walk — or a hike, if you’re on vacation. You can have an “exercise snack,” which is a tiny fitness session that can last anywhere from 30 seconds to five minutes. It can be anything that gets your heart rate up: running up a flight of stairs, doing 20 jumping jacks, skipping rope, or doing squats or push-ups. A few exercise snacks throughout the day can add up to a respectable amount of vigorous activity.