How Quickly Can You get 'Out of Shape'?

When it comes to muscle strength and endurance, we’ve all heard the saying, "If you don’t use it, you’ll lose it.” The real question is however, how long after you stop exercising before you start losing that muscle strength and endurance that you’ve worked so hard for?

The loss of fitness when you stop exercising is also known as detraining or deconditioning and can be impacted by a number of things, such as age and nutrition, but the main determining factors are:

  1. How fit you are.
  2. How long you have been exercising.
  3. How long you stop exercising.

Now most of the time people stop exercising because of illness, injury, holidays, work, travel, family, or social commitments and it’s because of these things that we often see a decline in our level of fitness. So how long does it take to notice this decline? According to an article published in the Journal of Applied Physiology in 2005 that looked at well-conditioned athletes who had been training regularly for a year and then stopped exercise entirely, it took about 3 months where researchers found that the athletes lost about half of their aerobic conditioning. Another study followed new exercisers for 8 weeks and during this time each individual made dramatic cardiovascular improvements and boosted their aerobic capacity substantially. However, only 2 months after stopping exercising the subjects had lost all of their aerobic gains and returned to their original fitness levels.

It’s all about supply and demand. If you stop running you take away the demand and so your ability to consume and process oxygen decreases, but not only that. Blood volume also rapidly decreases, which affects oxygen uptake. Mitochondrial density, lactate threshold, and the ability to oxidize fat stores all decrease. Even the enzymes involved in metabolizing energy decline and become less active. So how do we prevent all this from happening if we can’t exercise on a regular basis anymore?

The answer is through cross-training and diet. According to one study that took inactive men and made them exercise 3 times a week, for 3 months, and then reduced their exercise to once a week, found that as long as the men exercised at 70% of their VO2 max, they retained their strength. Another study conducted by the Department of Human Movement Sciences looked at the retention of muscle and endurance through diet alone and according to this study, when a muscle is going through disuse it’s energy requirements are appetite and reduced greatly. This then causes food intake to generally decline, resulting in an inadequate dietary protein consumption to allow for proper muscle mass maintenance. Maintaining protein intake during a period of muscle disuse can help slow down muscle atrophy from disuse.



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