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How long does it take to get unfit?

Published: 
Friday, August 21, 2015
Dirt Under the Nails

There are those of us who, if we miss a week of exercise, catastrophize and somehow feel that we have lost some of our fitness. There are also those of us who have missed months, and even years of exercise, and find it extremely difficult to re-enter into a fitness routine because even a 15 minute jog is exhausting. But just really how long does it take to get out of shape, to lose fitness?

I despise this answer, but it is often true…it depends. Thankfully, it takes longer than we may think! The body is a highly adaptable piece of engineering and responds to stresses placed upon it. If it is regularly stressed with physical activity, the systems of the body will adapt over time so that they can better handle such physical demands. That is how we become fitter and stronger.

However, if it is not required to perform such high level activity, there is no need (or stimulus) to get fitter. It will therefore remain in the state needed to perform the regularly required level of activity, be it lying on the couch or sitting at a desk all day. A body at rest stays at rest. That’s how we become detrained…a fancy way of saying that we have logged more hours at our desk than in our running shoes.

Different systems in our body lose fitness at different rates, but generally speaking, it takes about 3-4 weeks to notice a considerable change in one’s fitness.

Let’s take recreational exerciser, Jane, for example. Jane is someone who logs about 3 days a week of physical activity and still has enough energy to run around after her terrible two-year old. Jane developed ChikV and was down and out for a month before she felt reasonable enough to resume her exercise program.

The first system that lost fitness was Jane’s cardiovascular system. With no physical activity over the last month, Jane’s ability to consume and utilize oxygen had diminished considerably. In fact, after just 10 to 14 days of sedentary behaviour, a person’s aerobic system begins to decline. 

Cardiovascular exercise causes the heart to become stronger. It can therefore handle more blood per heartbeat. More blood can also get to the muscles involved in the exercise because of the development of a capillary network within those muscles. However, during detraining, those capillaries wither, and the heart loses it’s ability to handle more blood. This is why we become short of breath and our muscles burn when we begin a training program after a long hiatus…the cardiovascular system is not strong enough to get oxygen to the working muscles. 

The muscular system is also affected by detraining, albeit less dramatically than the cardiovascular system. We lose muscular strength and endurance after about 4 weeks of inactivity. During the first few weeks, the effects are barely noticeable, but after the four-week mark, muscle fibres begin to shrink. Muscles lose their “bulky” feeling, becoming softer, smaller and weaker. However, there is something to be said for muscle memory, and usually upon resumption of training, it is fairly easy to regain muscular performance. 

Jane’s body composition would also have changed during her illness. Contrary to popular belief, muscle does not turn into fat after a few weeks of inactivity. Both tissues are completely different. Rather, their proportions within the body are affected by exercise, or lack thereof. Jane stopped her workout that would usually burn 500 calories.

She therefore would have had to reduce the amount of food eaten in order to maintain her weight. If this was not done, the extra 500 calories that would have been burned during exercise, would have been deposited around her body in the form of fat. Couple this with muscle shrinkage and the result is a pudgy Pillsbury Doughboy.

While the above is the general rule of “use it or lose it,” the amount of fitness lost per period of time is different between trained and sedentary individuals. Research has shown that athletes retain a larger percentage of their fitness compared to sedentary people. They experience an initial decline in their fitness, but long term gains in physical fitness are usually minimally affected by time away from aerobic activity. 

However, athletes may feel the initial decline in function more intensely, as detraining occurs in proportion to the effort placed into getting fit. The fitter the person, the faster the fitness loss. There is so much more fitness to lose!

Detraining in inevitable as we go through different experiences and stages of our lives. The good news is that these changes in the body’s systems due to detraining are all reversible. So Jane need not worry! Her fitness should return pretty quickly!

Carla Rauseo, DPT, CSCS, ATRIC is a Doctor of Physical Therapy and a Certified Aquatic Therapy Rehabilitation Instructor at Total Rehabilitation Centre in San Juan. http://www.totalrehabtt.com

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