Don't kill yourself with exercise

Be cautious if you are launching an exercise program for the first time. Dr. Terence Kavanagh, Cardiac Health Foundation, warns:

     “We know from studies that if you don’t exercise at all and you engage in a sudden bout of vigorous activity, you can increase your chances of having sudden death by a hundred times, a hundred fold.”

But with patience and proper precaution, exercise can accomplish great things. Dr. Kavanagh, a cardiologist and Canada’s best-known authority on exercise and fitness, has demonstrated that. His guidance has helped thousands restore or maintain vigorous fitness and health. Seven of his patients were the first heart attack survivors to enter and complete the grueling 26-mile Boston Marathon.

     Increasingly the experts agree that moderate exercise provides the best returns in improving or maintaining physical fitness. Too little does no good. Too much takes you past the point of rapidly diminishing returns and into the realm of increased risk of injury or health damage. Unless you are an aspiring professional athlete, enjoy 10-mile runs, or want to compete in a triathlon, the surprisingly small additional health gains that result from more than just brisk and regular exercise are probably not worth the effort and risk.

     But while the experts agree that there is probably an optimum amount of exercise for each of us, in terms of effort and fitness rewards, they don’t all agree on what that is.

     There are generally considered to be three components of physical fitness: body weight and composition; muscular strength, endurance and flexibility, and aerobic or cardiovascular fitness. While aerobic fitness generally ranks first, muscular strength and flexibility are also important.

     Exercise is usually measured three ways: frequency (generally the number of times per week); duration (how long you exercise each time), and intensity (how hard your heart, lungs and muscles work, usually measured by how fast your heart beats).

Exercise can be classed as either anaerobic or aerobic. During the intense exertion of anaerobic activity, we consume oxygen at a faster rate than our cardiovascular system can supply it. In effect, we borrow the oxygen from glucose and glycogen, stored in our liver and muscles. We can keep this up for no more than two minutes, at most, after which we are left huffing and puffing as our systems attempt to pay back the borrowed oxygen. Running as hard as possible to catch a bus or being chased up a tree by a grizzly bear are forms of anaerobic activity.

     Anaerobic exercises are great training for football players, sprinters, and weight lifters. But most of us will get greater benefits from aerobic exercises, conducted at a slower pace, which does not exceed the capacity of our systems to deliver the needed oxygen.

     “For maximum cardiovascular benefits, nothing can take the place of aerobic exercise performed at your heart training rate,” according to researchers at the School of Public Health, University of California, Berkley.

     But how frequently and how long should we exercise? Three to five times a week is commonly recommended. “If you can’t exercise regularly, you’re better off not exercising at all,” says Dr. Kenneth H. Cooper, founder of the 650-staff Cooper Aerobic Centre in Dallas, Texas.

     Dr. Kavanagh recommends an optimum 60 minutes a day at your heart target rate, five days a week. More seems hardly worthwhile: “Those with the time and inclination to train seven times a week show maybe an additional one or two percent increase,” according to Dr. Kavanagh.

     Guidelines issued jointly by the American College of Sports Medicine and the American Heart Association in 2007 recommend either moderately intense aerobic exercise 30 minutes a day, five days a week; or “vigorously intense” exercise 20 minutes a day, three days a week. In addition to aerobic exercises, the guidelines also call for strength training exercises twice a week, with eight to 10 different exercises, each to be repeated eight to 10 times.

     But you may need to do more. “The 30-minute recommendations is for the average healthy adult to maintain health and reduce the risk for chronic disease,” the ACSM and AHA state. If you want to improve your fitness or lose weight, “60 to 90 minutes of physical activity [five days a week] may be necessary.”

     The advice for adults over 65, or those with chronic conditions, such as arthritis, is, “If you can exceed the minimum recommendations, do it.” It also advises seniors to “develop an activity plan with a health professional to manage risk and take therapeutic needs into account.”

     And here’s a helpful tip, if you’re hard pressed to find the time to exercise: “Research shows that moderate-intensity physical activity can be accumulated throughout the day in 10-minute bouts, which can be just as effective as exercising for 30 minutes straight.”

     TAGS: Exercise death risk. Heart attack. Myocardial infarction. Kenneth Kavanagh. Anaerobic exercise. Aerobic exercise. Cardio vascular system. Exercise frequency. Exercise duration. Exercise intensity. Heart training rate. Kenneth H. Cooper.