What happens when you stop working out?

Whether you’re just getting back to the gym or committed to a monthslong training program, sometimes life can get in the way of your fitness goals. A big project at work or a nagging injury can sideline even the most dedicated fitness enthusiast. But if you stop working out, how quickly will you lose your fitness level?

According to Daniel Morrissy, DO, a sports medicine physician at Einstein Healthcare Network, the detraining effect can kick in within the first 48 hours.

Morrissy said your body experiences a loss of blood volume, which makes the cardiovascular system work harder to deliver oxygen to your muscles. The metabolic pathways in your cells also become less efficient at burning fuel and clearing lactate.

“Athletes may feel these effects if they try to compete but there won't be any visible changes,” Morrissy said.  

Some athletes may also experience increased fatigue and appetite within 48 hours, said Cory J. Keller, DO, assistant professor of orthopaedic surgery and sports medicine at the Lewis Katz School of Medicine, Temple University.

Within the first week of stopping exercise, white blood cell function decreases which leads to increased susceptibility for infections, Keller added.

However, a drop in performance is one of the biggest effects of detraining, which would be noticeable within two weeks.

“Strength can be maintained longer than endurance,” Morrissy said.

Morrissy laid out exactly what happens to your body the longer you are away from your workout:

At two weeks: You’ll experience decreased cardiovascular efficiency and your ability to ventilate or exchange carbon dioxide reduces. When you exert yourself, your heart will beat faster and you will breathe harder. Your endurance can be reduced up to ten percent.

At four weeks: There is a measurable decrease in the size of the heart chambers and thickness of the heart walls. The density of capillaries, tiny vessels that supply oxygen and fuel to tissues, is reduced in your muscles. Muscle volume will decline in strength-trained athletes. The body will build up lactic acid earlier during exercise and have more difficulty clearing it. 

At eight weeks: Those who have only been training for a few months will return to pre-training levels of endurance. The same goes for any adaptations made by muscle fibers. Your maximal oxygen uptake or VO2max will begin to plateau.   

At 12 weeks: All gains made by training will be lost. The metabolic efficiency, cardiovascular and respiratory conditioning, and structural strength will have returned to sedentary levels. 

According to Jonathan Daddis, a trainer at Weston Fitness with Revolve Athletics, you may also experience some psychological effects of detraining. We know that the endorphins and adrenaline we get from physical activity provide us with more energy throughout the day.

“When that stops, low energy, even depression can set in,” Daddis said. “The longer we abandon our training the harder, psychologically, it is to get back at it.”

A little is better than none

Unless you are experiencing serious injury or illness, try not to abandon your workout completely.

According to Morrissy, strength can be maintained with as little as one session per week and endurance can also be maintained with a decreased volume of training.

“The key is maintaining the intensity of the workout,” Morrissy said. “One can decrease the duration or number of workouts as long as the intensity remains high.”

And if a lack of time is your biggest hurdle, remember that a little is better than nothing at all.

“Even 10 to 15 minutes of moderate exercise three times a week can ward off some of the symptoms of exercise withdrawal,” said Keller.