How Fast Do I Lose Fitness If I Stop Exercising?

Deconditioning, or losing fitness, when you stop training due to illness or injury is one of the six principles of conditioning (listed below). The principle of use/disuse refers to the ‘use it or lose it’ concept. However, how quickly you lose fitness depends on how fit you are, how long you have been exercising and on how long you stop.

Deconditioning theories are becoming more clear thanks to several research studies focused on aerobic fitness. One study had well-conditioned athletes who had trained for a year stop exercise all together. After a three-month hiatus, researchers found that the athletes lost about half of their aerobic conditioning. New exercisers, however, did not fare as well. Another study followed new exercisers through the conditioning and deconditioning process.

Sedentary individuals started a bicycling program for two months. During that time they made dramatic cardiovascular improvements and boosted their aerobic capacity substantially. Then, they quit exercising for the next two months. When re-tested, the researchers found that these new exercisers lost all their aerobic gains and returned to their pre-training fitness levels.

There is also research being conducted that looks at decreases in training level, rather than completely stopping all exercise. The results are very promising and should provide comfort to athletes who need to cut back on training due to time constraints, illness or injury. One study followed sedentary men through three months of strength training, three times a week, and then had them cut back to one session per week. They found that these men maintained nearly all the strength gains they developed in the first three months.

There are also many individual differences in deconditioning rates, and it is impossible to apply all these studies to your situation. But it appears that if you can maintain some exercise on a weekly basis, you can maintain your fitness levels fairly well.

If you do need to stop exercise completely for several months, it is difficult to predict with accuracy how long it will take you to return to your former fitness levels. Again, individual differences come into play. Some research shows that after a three-month break, you cannot return to peak condition in a week. In some cases, it takes as long as three months to regain all your conditioning. Here again, it seems to depend on your original level of fitness and how long you stopped.

For athletes who need to take time off, try to do something at least once a week during your break, but don’t quit completely. Cross training through an injury is always a great option.

Six Principles of Conditioning

1. The Principle of Individual Differences

Because every athlete is different, each person’s response to exercise will vary. A proper training program should be modified to take individual differences into account. Some considerations:

  • Large muscles heal slower than smaller muscles.
  • Fast or explosive movements require more recovery time than slow movements.
  • Fast twitch muscle fibers recover quicker than slow twitch muscle fibers.
  • Women generally need more recovery time than men do.
  • Older athletes generally need more recovery time than younger athletes do.
  • The heavier the load lifted, the longer it will take the muscles to recover.

2.  The Principle of Overload

The principle of overload states that a greater than normal stress or load on the body is required for training adaptation to take place. The body will adapt to this stimulus. Once the body has adapted then a different stimulus is required to continue the change. In order for a muscle (including the heart) to increase strength, it must be gradually stressed by working against a load greater than it is used to. To increase endurance, muscles must work for a longer period of time than they are used to. If this stress is removed or decreased there will be a decrease in that particular component of fitness. A normal amount of exercise will maintain the current fitness level.

3. The Principle of Progression

The principle of progression implies that there is an optimal level of overload that can be achieved, and an optimal timeframe for this overload to occur. Overload should not be increased too slowly or improvement is unlikely. Overload that is increased too rapidly will result in injury or muscle damage. Exercising above the target zone is counterproductive and can be dangerous. For example, the weekend athlete who exercises vigorously only on weekends does not exercise often enough, and so violates the principle of progression.

The principle of progression also makes us realize the need for proper rest and recovery. Continual stress on the body and constant overload will result in exhaustion and injury. You should not (and can not) train hard all the time. Doing so will lead to overtraining and a great deal of physical and psychological damage.

4. The Principle of Adaptation

Adaptation is the way the body ‘programs’ muscles to remember particular activities, movements or skills. By repeating that skill or activity, the body adapts to the stress and the skill becomes easier to perform. Adaptation explains why beginning exercisers are often sore after starting a new routine, but after doing the same exercise for weeks and months the athlete has little, if any, muscle soreness. This also explains the need to vary the routine and continue to apply the Overload Principle if continued improvement is desired.

5. The Principle of Use/Disuse

The principle of use/disuse implies that you “use it or lose it.” This simply means that your muscles hypertrophy with use and atrophy with disuse. It is important to find a balance between stress and rest. There must be periods of low intensity between periods of high intensity to allow for recovery. The periods of lower intensity training, or the rest phase, are prime times for a bit of crosstraining.

6. The Principle of Specificity

The Specificity Principle simply states that training must go from highly general training to highly specific training. The principle of specificity also implies that to become better at a particular exercise or skill, you must perform that exercise or skill. To be a good cyclist, you must cycle. The point to take away is that a runner should train by running and a swimmer should train by swimming.


About the Author

Elizabeth Quinn, M.S., is an exercise physiologist and health information writer and researcher. She currently manages the clinical health information development for a NW health care organization.


Elizabeth has worked as an exercise physiologist in sports medicine clinics, corporate wellness facilities and rehabilitation clinics. A former national silver medalist in road and track cycling, Elizabeth continues to participate in recreational cycling, mountain biking, running, skiing and almost anything else that requires movement.

Elizabeth has a master’s in exercise science and bachelor’s in psychology. In addition, she has worked as an ACE certified Personal Trainer, and a professional member of ACSM. 

From Elizabeth Quinn:
“Sports Medicine has a reputation of being reserved for professional athletes, but anyone who is active can benefit from understanding the basics of sports medicine.”

Originally published in 2014 print issue.