Nobody can exercise vigorously in the same sport every day. If you think that you can, expect to be injured. All athletic training is done by stressing and recovering. It's called the hard-easy principle. On one day, you exercise vigorously and your muscles feel sore. Then, for the next few workouts you exercise far less intensely until the soreness disappears. Only then should you attempt another hard workout.if you do not compete in sports, it is better to exercise only every other day or to alternate sports that stress different parts of your body. For example, on one day, you could stress your legs on your stair-stepper. On the next day, you could stress your back and shoulders by pulling on a rowing machine. The hard-easy principle applies to your skeletal muscles, not your heart. You can exercise hard on consecutive days as long as you do not use the same set of skeletal muscles. It's much better to exercise vigorously one day and take the next day off than to just lollygag along every day.
Cross Training Reduces Athletic Injuries
Triathletes are injured only one third as often as marathon runners even though they do far more work, swimming, cycling and running. Training intelligently for three sports is less likely to injure you than training too hard for one. Training is limited by damage to skeletal muscles. Every time you exercise, your muscles develop small tears with bleeding. It takes at least 48 hours for muscles to heal from exercise. Each sport stresses a particular group of muscles most. Marathon runners train every day and stress the same muscles that have not had adequate time to recover from the previous day's workout, so they are at increased risk for injury.
On the other hand, top triathletes train at different sports on consecutive days. Running stresses the lower leg muscles most, cycling stresses the upper leg muscles most and swimming stresses the arms and shoulders most. Triathletes should set up a
workout schedule that includes two sports on one day and one on the next. Of the three sports, running causes the most muscle damage. Muscles are protected by the water in swimming and by the rotary pedal motion in cycling. However, the force of the footstrike in running tears up muscles. So a knowledgeable triathlete runs on one day and cycles and swims on the next.