Focus on Fitness: How your body changes when you stop exercising

By Gloria Schwartz

There are times when sticking to an exercise routine becomes difficult and you may be unable to exercise for a few days or a week. Sometimes circumstances prevent you from getting in your strength training or cardio workouts for an extended period of time, such as a few weeks or months. You may have an injury or illness, a hectic schedule, or simply a lack of motivation. Maybe you’re away on vacation. Unfortunately, you can’t bank exercise. Most of the physiological benefits of exercise start to wane just a few weeks after you become inactive. You may know from experience that when you don’t exercise, you get weaker, slower and fatter; but what actually happens to your body when you take an extended break from exercise?

The level of decline you experience when you stop exercising is based on factors such as your age, gender, genetics and fitness level. One of the first things you’ll notice is a decrease in your physical endurance. You may get out of breath more easily. This is because your maximal oxygen uptake (VO2 max) decreases. VO2 max measures the difference between the oxygen concentration in the blood leaving the heart and returning to the heart. Regular endurance exercise leads to improvements in your heart, blood vessels, capillaries and mitochondria; therefore, your body more efficiently uses oxygen and nutrients. After refraining from cardio exercise (e.g., High Intensity Interval Training, running, aerobics classes, swimming, cycling, brisk walking) for just two weeks, your VO2 max can decrease by 10 per cent and in three months by 20 per cent.

Just as exercise has positive effects on the brain in terms of neurogenesis, cognition and emotional state, lack of exercise has negative effects. A study of master endurance runners (over age 50) found that after 10 days of exercise cessation, they had decreased blood flow to various parts of the brain, though they
did not experience immediate cognitive changes ( Taking an extended break from exercise can impact your mood. You may feel depressed, anxious or lacking in energy as the levels of your neurochemicals (e.g., dopamine and serotonin) and hormones (e.g., cortisol) change.

Strength seems to decrease at a slower rate than endurance. After two to four weeks without strength training, you lose some of your strength and muscle tissue. After six to eight weeks, you may start to gain body fat and feel your clothes not fitting as well as your waist circumference increases. Muscle does not turn into fat. If you stop working out, you don’t need as many calories. If you keep eating the same way as when you worked out, you’ll gain body fat. Even very athletic people experience these unwanted changes. For example, a study measuring body characteristics of collegiate swimmers and divers before and after a training season found significant changes in body composition following a break from training. The athletes had an increase in body fat, body weight and waist circumference and a decrease in muscle mass, even though they were not completely sedentary during that period.

Flexibility can decrease by as much as 30 per cent within just four weeks of inactivity. You may also experience a decline in speed, power, agility and coordination.

If you’re not concerned about losing strength, endurance or flexibility, perhaps you’ll be convinced to return to a good exercise routine when you realize that your blood pressure and glucose levels can sharply rise when you become sedentary. Almost 50 per cent of the gains you made from your commitment to exercise are lost after just two weeks of inactivity. This can be a serious health concern, especially if you have diabetes or high blood pressure. A study of overweight, previously sedentary people who did strength and aerobic exercises for eight months lost almost half of the improvements to their blood glucose levels after just two weeks of inactivity ( Another study found glycemic control decreased in healthy, active men who reduced their daily activity by half for just five days, walking 5,000 instead of 10,000 steps per day.

The good news is that if you get back into a good exercise routine, you can slowly and safely return to your previous level of fitness, though it may take longer to regain it than it did to lose it. Even if you’ve been sedentary for years, it’s never too late to start.