Most people understand the benefits of regular fitness — a better figure, improved strength and dexterity and more stamina — but few are aware of what happens to your muscles when you stop training and allow them to be inactive.
As your body transitions to a sedentary state, the muscles undergo a reversal. Understanding how muscles work and what happens to them when you stop exercising will help you in structuring a workout regimen and ensuring the maintenance of your muscle mass and definition.
Muscles don't turn to fat when you stop weight training. They do however, lose mass. Any fat gain you notice will come from eating the same amount you were eating previously, or more, and not exercising to burn calories.
How Muscles Work
When you exercise, your body does not actually create new muscles. Instead, your existing muscles grow larger and stronger, and the number of capillaries — the networked blood vessels between arterioles and venules — increases.
With regular exercise, muscles also develop more mitochondria — this is where biochemical processes of respiration and energy production occur in the cell. The result is larger, more defined muscle mass, not newly created muscle tissue.
The American Council on Exercise says some people have it imprinted on their DNA to grow larger muscle mass than others. But muscle is muscle regardless, and whether it's large or small, and whether you weight train or not, your muscles will still be there.
From Exercise to Inactivity
Adopting a sedentary — or inactive — lifestyle has the opposite effect on your muscles. The increased blood flow previously needed to fuel your cells during exercise is no longer required, and your body begins to contract and reduce the size of your capillaries.
You may be afraid that muscles turn to fat or disappear, but instead all they do is shrink and decrease in mass. Fat may be produced if your diet provides your body with more calories than you require for the level of activity you maintain, according to the National Academy of Sports Medicine, but your body doesn't magically transform muscle into fat.
Read more: Positive and Negative Effects of Exercise
Don't Let Your Muscles Atrophy
While stopping exercise may decrease the size of your muscles, extremely poor nutrition, starvation and disease can cause muscle atrophy, where muscles can completely waste away.
Without the calories, vitamins and nutrients of healthy food, your body is thrust into a state of malnutrition. Not only does this cause permanent damage to other organs, but it can also lead to death.
Maintaining Your Muscles
Keeping active and following a healthy diet means maintaining your muscle mass and preventing the accumulation of excess body fat.
The Physical Activity Guidelines for Americans recommends 150 to 300 minutes of moderately-intense cardio a week to maintain health and a decent level of physical fitness; and at least two days of strength training.
If you don't care to lift weights for whatever reason, you can perform bodyweight exercises like push-ups, lunges and squats every couple of days to help keep your muscles active and your body limber.
Outside of weightlifting tournaments or training for a triathlon, devoting at least 20 to 30 minutes a day to activity will keep your muscles healthy and ready for whenever you need them.