For everything that is good, there is probably a limit on how much is beneficial. This is certainly true for exercise. The benefits of exercise are unequivocal, but too much exercise can hurt us. Exercise places a stress on the body that results in temporary fatigue. We then rest, recover, and adapt. We get better; tissues gain strength and bones develop, but if the stress is either too high or the recovery too little, maladaptation occurs. Functionality decreases, injury occurs. This is how we develop overuse injuries. Balancing what is good for us and what is too much is our challenge.

Overuse injuries are different from the single event injuries we observe when watching sport. Sprained ankles and hamstring tears are immediately diagnosed and treated, but overuse injuries are subtle, creeping up on you, starting with a little pain and stiffness. We tend to ignore these, especially since the symptoms go away when exercise begins. But if not treated, symptoms don’t go away, worsen, tissues are further damaged, and recovery lengthens. Our tendency toward excess has resulted in a profound increase in overuse injuries.

Not surprisingly, overuse injuries in children are now the predominant injury presented at sports medicine clinics. People of my generation remember when sport, especially children’s sport, was played seasonally. Overuse injuries were unheard of as children switched from sport to sport, giving their bodies time to heal and recover. There is little doubt that the drive for children to specialize in one sport year round is one cause. The mistaken belief that children need to specialize early to succeed has led to a dramatic rise in overuse injury as well as burnout.

So many sports are now played year round, but one cannot stay in top condition year round. A good example of year round overuse is related to baseball Showcases. We have always known that pitching injuries are highly related to the number of pitches a player throws. Former baseball coach Jerry Ford started the first baseball Showcase in 1993, purported to evaluate players. Since events were held during the offseason, players had no time to rest, and they couldn’t rest since pitching velocities were posted nationwide. Boys were pressured to maintain top velocity all year. Today, there are more Showcases, making lots of money, and players who attend Showcases are four times more likely to suffer injury.

Overuse injuries have always been common for adult exercisers. Training error causes overuse injuries. Tennis elbow, runner’s knee, and shin splints are all caused by overuse and the absence of rest. People who never vary their workouts, performing the same mind-numbing exercise day after day are susceptible. Increasing your routine too severely results in overuse. To prevent overuse, change routines, play different sports, rest between hard days, take time off, and observe the 10-percent rule when increasing your program. That is, only increase a maximum of 10-percent a week.

Caution must accompany one learning new skills. First, the tissues that surround the joint are not prepared for the stress. Second, when these tissues fatigue, joint laxity increases, causing damage. So practice in spurts, mixing up drills so that one joint does not take all the stress. For example, setting up a ball machine and hitting endless backhands will place significant stress on your elbow and shoulder. Instead, mix up your shots. After all, that’s what you do when you play. Practice should imitate play. If the game is played in intervals, practice should be interval.

Overuse injuries affect most tissues, but tendons, bones, and the muscle-tendon unit are most affected. The word commonly given to these tendon injuries is tendinosis. These are not inflammatory injuries but actual damage to the tendon and muscle. Stress fractures, a common overuse injury, are small cracks in the bone. Taking anti-inflammatory medications and ice may help with discomfort, but the treatment for overuse is rest.

Finally, I have to wonder when there is an end to endurance? For years we recommended jogging 12-15 miles a week. People then wanted to test themselves by the ultimate test, running 26.2 miles (a marathon). Today, we have ultramarathons and 100-mile races, some with significant altitude changes. There is the occasional 200-mile race. I have seen microscopic tissue samples before and after marathon races. The beautifully-organized parallel muscle fibers prior to a race look like a plate of spaghetti afterward. I can’t image what 100 miles might do.

Jim Johnson is a retired professor of exercise and sport science after teaching 52 years at Smith College and Washington University in St. Louis. He comments about sport, exercise, and sports medicine. He can be reached at jjohnson@smith.edu]]>