What Really Happens to Your Body When You Stop Working Out
If you started lifting weights in high school or college there’s a good chance you had someone along the way try to sell you the “no days off” mantra. While we’re now smart enough to know rest days are actually essential for preventing injury and boosting recovery, there are some downsides to too many days off.
In the last decade, most researchers agreed if you took two weeks off from the gym, you were not only bound to lose all your gains, but you’d suffer some pretty serious psychological issues in the process. However, according to new research, even 10 weeks off from the gym doesn’t deteriorate muscle size and strength nearly as much as previously thought.
In fact, “for the group training continuously for 20 weeks, progress clearly slowed after the first 10 weeks,” says PhD Student Eeli Halonen. “This meant that there was ultimately no difference in muscle size or strength development between the groups.”
Of course, how much and how quickly you’ll decondition depends on a slew of factors like how fit you are, your age, and how long sweating has been a habit.
If you’re about to go on a workout hiatus, due to injury, workload, or desire to take some time off, here’s what to expect—and how to make a comeback.
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5 Things That Happen When You Stop Working Out
Despite all of its abilities, the human body (even the fit human body) is a very sensitive system—and physiological changes (muscle strength or a greater aerobic base) that come about through training will simply disappear if your training load dwindles, he notes. Since the demand of training isn’t present, your body has nothing to adapt to—and simply slinks back toward baseline.
1. You’ll Become Deconditioned
Have you ever taken a week off of the gym because you were sick only to feel like you lost all of your strength? This process is known as deconditioning. Simply put, deconditioning is a state of physical decline that occurs due to prolonged inactivity. Just as a good training program builds you up, falling off the workout wagon can have the opposite effect—sometimes almost immediately. Fortunately, the condition is fully reversible, as long as you get your butt back to the gym.
Many signs of deconditioning are not always physically visible to the naked eye—but you should expect a loss of muscle mass and size and the accumulation of body fat, says Tom Holland, C.S.C.S., an exercise physiologist. If you don’t make any changes to your diet, you could gain a few pounds in this timeframe, adds Pete McCall, an expert exercise physiologist at the American Council on Exercise.
You might notice your performance slip, too: “Speed, endurance, and strength can decrease by 25 to 30 percent within two to three weeks,” says Weiss.
2. You’ll Lose Muscle Mass
For anyone panicking as they read, here’s your reminder that Rome wasn’t built in a day and it won’t crumble in one either. According to a 2022 review of 20 randomized and non-randomized trials, individuals who regularly trained their strength to a max capacity maintained their gains even after a 16- to 24-week period.
After months or even years of time off you are bound to see a sizable decrease in muscle mass, capillary size, and density; bone density; flexibility; and overall blood flow and energy production are all side effects of becoming a couch potato, says Weiss.
And while your body will hang onto strength gains longer than aerobic gains, throwing in the proverbial exercise towel will gradually lead to a loss of lean muscle mass, muscular strength, endurance, and neuromuscular training adaptations, explains Holland. Read: Beyond size and strength, your muscles simply won’t fire the same way they used to because of underuse.
What’s happening? As muscle fibers realize they don’t need to store energy, they will store less glycogen—which leads to something called atrophy (or the shrinking of muscle fibers), explains McCall. When muscle fibers shrink, they need more stimuli to contract, he explains. So you’ll have to work harder to see results.
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3. Your Aerobic Capacity Will Lessen
Dylan Coulter
“Aerobic and endurance fitness reduce a lot faster than muscle mass—it’s the performance factor that’s reduced the fastest,” says Weiss. Physiologically, the changes are stark, too. Weiss says: Stroke volume (the amount of blood pumped out of the heart to the body) reduces, the size of mitochondria (the power plants within a cell, linked to fitness health) reduces by almost 50 percent, heart rate increases, cardiac output reduces, and your VO2 max—or the maximum volume of oxygen an athlete can use (a gold standard of physical fitness) decreases about one percent a day.
Another setback: Your lactate threshold—or how hard and long you can work out until your muscles tell you to stop—begins to drop, says Holland. (This stinks because working out at or close to your lactate threshold is a great way to build fitness; if yours is low you won’t last very long, and thus you’ll reap fewer benefits from a gym session.) “You begin to lose endurance capability as well as the ability to perform at higher intensities,” adds Holland.
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3. You May Experience Cognitive Decline
Since exercise helps pump oxygen to the brain—one reason why you may feel sharp after a workout—you may feel a little cloudy or not as ‘on’ after weeks removed from your workout regime, notes McCall.
One factor at play: Both aerobic and strength training boosts the neurotransmitter brain-derived neurotrophic factor (BDNF), which helps promote the growth of new brain cells and enhances connections between existing ones. Some research even links low levels of BDNF to depression. “This makes exercise an important part of maintaining cognitive function,” he says.
Dopamine levels also drop as your days in the gym become a thing of the past, which may make you more anxious and fatigued, says Weiss. This feeds into motivation—if you’re tired and stressed you may avoid the gym, creating a vicious cycle. “The longer the time off, the more difficult a time people have starting up once again,” says Holland.
5. Your Sleep Will Suffer
Because exercise places both metabolic (or energetic) and mechanical stress on your muscle tissue, it can help promote good sleep, says McCall. After all, it’s in deep REM cycles of sleep that your body produces hormones (like growth hormone and testosterone) to repair muscle tissue damaged during exercise, he notes. “A lack of exercise will lead to higher levels of energy in the body and reduce the need for deep sleep, which could lead to restless or insufficient sleep.”
Related: These 2 Simple Workouts Can Improve Your VO2 Max in Record Time for HYROX and Beyond
5 Ways to Comeback From a Workout Hiatus
Use these expert tips from Greg E. Bradley-Popovich, C.S.C.S.
1. Stay Sharp
Visualize your sport: Wear your workout gear and do mental exercises within your normal workout environment. Eventually, your brain won’t be able to tell the difference between real and imagined practice. If you play a team sport, hang out with your teammates to prevent feelings of isolation.
2. Train Smarter, Not Harder
Exercise without jeopardizing your recovery if you’re coming off an injury—or doing too much too soon if you’re just coming of a hiatus. Ease into sessions and be realistic.
3. Eat Wisely
Start by curtailing calories if you’re taking a break from working out. Since you won’t be active, there’s no need to eat as much. Also, cutting back on the amount of food you eat will reduce your chances of gaining unwanted weight.
Sam Kaplan
4. Consider Supplements
Essential amino acids can help a muscle tear heal. Glucosamine and chondroitin give your body raw materials for joint-surface repair, while gelatin is an important component for connective-tissue healing. Broke a bone? Make sure you’re taking in adequate calcium, phosphorus, and vitamin D.
5. Take Creatine
Research shows creatine can speed healing of nerve injuries, offset the effects of mental fatigue, slow strength loss during a training hiatus, stimulate satellite cells that help muscles heal, improve glucose metabolism, restore glycogen stores during immobilization, and facilitate strength and power gains during rehabilitative exercise. Basically, it does everything. So chug away.