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The Dangers of Inactivity

by Margaret Barr, B.Sc.(P.T.), M.A.

A few weeks ago I met with my friend Ed, who has lived with rheumatoid arthritis (RA) for 40 years. Ed has so many artificial joints he calls himself the bionic man. He doesn’t move too fast these days. But Ed is a top-notch and passionate bird photographer, and over the years he’s been creative in finding ways to stay mobile. Last fall, Ed had surgery to stabilize a subtalar joint (a joint in the foot). The surgery was more complicated than he had expected, and he was unable to bear weight on the foot for several months. “The inactivity played havoc with my RA, and of course I went into a flare,” Ed told me over coffee.

It’s been almost 20 years since John Bland, a rheumatologist, talked about “the perils of inertia.” Even the oldest and weakest among us can become some kind of athlete, he claimed, but only the strongest of us can survive as spectators in the arena of life. An avid skier in the 75–79 age group, Bland knows that bodies work best when they move. So what happens to the body when it doesn’t get enough exercise?

What happens is called deconditioning, and this article will look at what deconditioning means for various parts of the body.

The heart

Muscles thrive with consistent and appropriate challenges, and the heart is one big muscle. Cardiac muscle is different from the skeletal muscle that moves our limbs, but most of the same principles apply when it comes down to fitness. To stay in shape, the heart needs to be challenged, and the heart is challenged by physical activity and exercise.

The heart pumps blood to supply both itself and the rest of the body with energy-producing oxygen and nutrients. Without a regular workout, cardiac muscle atrophies — the heart shrinks. The result is a weakened and less efficient pump, which pumps less blood with each stroke, so that the heart rate (the speed of pumping) has to increase to make up for the lack of pumped volume. Blood flow becomes sluggish, making the blood vessel walls more susceptible to plaque formation. The blood channel narrows, contributing to further loss of efficient blood flow and to higher blood pressure. The transfer of oxygen and nutrients from capillaries (microscopic blood vessels) into skeletal muscles, body organs, and tissues slows down. This is partly because the number of capillaries is reduced, and partly because there are fewer transfer sites in the cell walls and fewer of the proteins that transfer oxygen and nutrients into the cells at these sites. The initial transfer of oxygen into the blood as it moves through the lungs is affected in a similar way. As well, hemoglobin, the protein that carries oxygen in the blood, is slower to pick up and release the oxygen — and there is less hemoglobin available.

And that’s only about the flow in one direction. Carbon dioxide — along with other waste products that collect in the blood from energy production and body repair and building processes — has the same kind of problem as it returns to the lungs to be breathed out. But there is an added difficulty for the returning blood — most of it has to fight the effects of gravity. Without a well-functioning pump, blood tends to pool in the extremities, increasing the likelihood of plaque formation in veins and causing the feet, ankles, and hands to swell. Plus, less effective circulation means a slower reaction to changes in body position, so that when you stand up quickly, blood doesn’t get to your head as fast as it should and you feel dizzy.

Energy levels

The cells of muscles, organs, and body tissues have energy-producing structures called mitochondria. Every function in the body requires energy produced by these little dynamos. To create energy, mitochondria need oxygen and carbohydrates. When oxygen supply is diminished or slowed, and when the waste products of energy production accumulate and aren’t removed fast enough (as occurs when the heart isn’t working efficiently), the number of mitochondria drops and the efficiency of each is reduced. So energy production slows down, you use the same amount of energy but get less work done, and fatigue sets in earlier.

Muscle and soft tissue

Whereas an increased heart rate is one of the cardinal signs of an out-of-shape heart, the signs of an out-of-shape skeletal muscle include a loss of muscle tone and strength. Each tiny filament of each fiber of every skeletal muscle needs the stimulus of work. Without work, the flow of blood in the muscle slows, and there is a decreased exchange of waste products and nutrients. Loss of mitochondria in the cells, as well as a decrease in filament overlap and muscle fiber size, translates into a slower speed of muscle contraction, reaction, and coordination. Much of this change stems from a degrading of the connection between the nerves and the muscles. That is, the tiny electrical impulses that tell muscles what to do don’t work as well when they are not used. This in turn leads to decreased strength, inadequate response times, and reduced ability to move. Add this problem to a shrinking muscle mass and the risk for injury increases.

Last Reviewed on August 22, 2012

Margaret Barr is a retired exercise consultant and freelance writer living on Vancouver Island in British Columbia.

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