I hate exercise. It’s uncomfortable, sweaty, and cuts into quality TV time.
Unfortunately, it’s good for you.
Exercise is physical exertion for the purpose of improving physical fitness. (If it’s for any other purpose, we call it “hard work.”) Modern fitness programs got their start in Prussia in the 1800s (which should tell you something). Feminists took up the idea to prove that women are not frail, and in fact the word “calisthenics” was coined in 1831 by the headmistress of an American girls’ school, from the Greek words kalos, “beautiful,” and shenos, “strong.”
The primary component of all exercise, from jogging to marathon ballroom dancing, is the contraction of skeletal, or “voluntary,” muscle. Hard-working muscles require more blood, carrying more oxygen. This means both the circulatory and respiratory systems have to work harder, which, over time, improves their efficiency.
The best place to see this improvement is in the people who exercise the most: trained athletes (such as the ones profiled in the IMAX film To the Limit, playing through the end of June in the Kramer IMAX Theatre at the Saskatchewan Science Centre–this is a plug). Athletes’ hearts are generally larger, beat slower and pump more blood than non-athletes’. Athletes are also up to three times as efficient as non-athletes at extracting oxygen from their blood. All of this means that during exercise athletes’ hearts are able to meet the increased demand without working as hard.
Assuming you’re not mountain-climbing while you read this, you’re consuming 250 to 300 millilitres of oxygen a minute. An endurance athlete at peak exertion consumes 20 times as much, more than six liters a minute. One liter of oxygen consumed corresponds to about five kilocalories of metabolic energy. (A kilocalorie, the energy required to raise the temperature of one litre of water one degree Celsius, is a “food” calorie.) So at peak exertion, an athlete is consuming 1,500 to 1,800 kilocalories an hour.
In the process the athlete’s endurance-trained muscle also burns less carbohydrate and more fat than does untrained muscle: another benefit, since the percentage of body fat, experts say, should not exceed 16 to 18 percent in men and 18 to 22 percent in women.
All of these benefits apply primarily to “aerobic,” or “oxygen-using” exercise, such as jogging. Weight-lifting, sprinting and other exercises that depend on quick bursts of intense effort instead of endurance overload the metabolic reactions that provide oxygen to muscle and make use of other biochemical reactions, instead. “Anaerobic” (non-oxygen using) exercises quickly build up compounds in the muscles that lead to fatigue. They build muscle strength, but do little to improve overall cardiovascular fitness.
Exercise has other effects. Body temperature increases: contracting muscle cells may increase total heat production 10 to 20 times. Rectal temperatures of 41.1 C have been recorded in long-distance runners–a temperature the body’s sweating mechanism would never allow for a person at rest: dehydration or even heat exhaustion would set in first. No one knows why the body allows such high temperatures during exercise, but there is evidence that skeletal muscle works better at temperatures above the “normal” 37 degrees.
In the longer term, exercise even helps offset aging. Older people who exercise, studies show, can maintain the capability to climb stairs or walk with as much vigor as an inactive person 20 years younger. Lean body mass, the percentage of the body that’s not fat, invariably decreases with aging, but exercise can help slow that process.
Exercise also appears to boost high-density lipoproteins in the blood. This is the so-called “good cholesterol, “good” because a high ratio of HDL to total cholesterol lowers heart disease risk. In one study, 60-year-old endurance athletes had a ratio of total to HDL cholesterol levels as low as for trained runners in their 20s.
Exercise also appears to improve psychomotor skills such as reaction time and balance. Another study showed 70-year-old women who had been regularly exercising for years had reaction times equal to those of inactive college women.
Weight-bearing exercises such as running and walking even appear to benefit the skeleton; research has shown men and women over 50 who have been running for years have spines 40 percent denser than a sedentary group of the same age.
The big picture? Exercisers live longer. (All right, who said, “At least it feels that way!”?) More than 3,000 healthy women who visited an aerobics clinic were studied for eight years; those that were less fit had a mortality rate 4 1/2 times that of the fitter women. Another study of 17,000 Harvard alumni found that over a 12 to 16-year period, those who had expended 2,000 or more calories a week in physical activity had a 28-percent lower death rate than their less active counterparts, equivalent to 2.15 years of added life.
“A sedentary person who goes into training can produce a response that may be the equivalent of a 10-year or even a 20-year rejuvenation,” says Dr. Roy J. Shephard, director of the School of Physical and Health Education at the University of Toronto.
Better health, more strength, longer life: there’s just no doubt about it–exercise is good for you.
So I do it.
But I still don’t like it.