Most injuries involve damage to what we think of as hard muscles, but what doctors refer to as soft tissue—namely pulls and strains. "Soft" refers to the fact that muscles are pliable, stretchable and bendable, which overall makes them pretty forgiving. Still, you have to respect their limits, not only to avoid short-term pain and inconvenience but also unforeseen trouble down the road. "Many injuries can have long-term ramifications physically and economically," Dr. Janda says. "I see people all the time who complain about injuries they got 25 years ago." If you avoid injuring muscles, you'll likely avoid damaging tougher parts of the body as well, such as bones, tendons and ligaments.

You  will realize that respect for the body's limits drives a lot of the concepts and principles we've discussed throughout. Here's a roundup of the most crucial ways to keep your body in action and your program on track.

The fact that different sports require specific forms of training means that each also involves particular types of injuries—and particular ways to avoid them. Here's how to protect yourself when doing three popular forms of exercise in which speed, balance, high impact or a combination of the three results in an unusually steep rate of injury.

 

Take a freeze-frame of a runner in midstride and what do you have? A guy who's airborne. A guy who's about to land on one foot with all his body weight, multiplied two to three times by the forces of gravity and forward momentum. With this kind of hammering, it's no surprise that when a study followed participants in an Atlanta 10-K race for ten years, 53 percent reported being injured. Here are some things you can do to improve your odds.

Body-Temperature Injuries

You don't need to smash, twist or grind your body to get it into trouble. There's also danger of damage that starts from the inside out. Let your body temperature swing too far to either end of the thermostat and you'll be facing potentially deadly problems. Here's how to keep your thermostat set in the temperate zone.

* Hypothermia comes about when low internal temperature interferes with the body's ability to regulate vital machinery like metabolism and heartbeat. One key factor is getting wet, which vastly increases heat loss in the cold. Wear clothes that wick moisture away from the body rather than holding it close to the skin. Polypropylene underwear is better than cotton in cool weather. "Avoid cotton—it's miserable when wet," says Andrew Dannenberg, M.D., assistant professor at the Injury Prevention Center of Johns Hopkins University School of Hygiene and Public Health in Baltimore. Another key factor is loss of energy. When you're active, body heat generally makes up for lost warmth, but you should head for shelter once intensity—and body heat—dwindles.

"There are between 800 and 1,000 bike-related deaths a year, but these are the tip of the iceberg in terms of total injuries," says Dr. Dannenberg. Here's how to ride safe.

Don't flip your lid. Most of the deaths Dr. Dannenberg refers to are from head injuries sustained in crashes. Insurance against this ugly eventuality comes in two parts. The first, of course, is not to take your head for a ride while your helmet languishes in your hatchback. The second is not to crash. Keep loose items (bags, shoestrings, arms of outerwear you've removed) out of spokes and chain rings. If you're riding on the pavement, watch out for unexpected obstacles such as opening car doors; if you're off-road, keep your speed within your abilities.

Pedal fast. Common sense says straining against the resistance of a high gear could make you more susceptible to overuse injuries. Spinning at lower gears tends to reduce strain and propel you more efficiently. Save the high gears for when you have sufficient speed to keep each pedal moving at the recommended 80 to 100 revolutions per minute for non-racers and 100 to 150 for racers, says Dale Hughes, director of the Walden School of Cycling in Rochester, Michigan, and chairman of the National Off-Road Bicycling Association.

Have a fit. If you do a lot of riding, it's common to experience knee and back pain from improper positioning on the bike. Ask a bike shop mechanic to check the position of your saddle, handlebars and pedals, says Dr. Janda.

The Perfect First-Aid Kit

It's part of the nature of accidents and mishaps that you're not prepared for them. After all, if you knew it was going to happen, it wouldn't have happened. That's why it makes sense to have handy a kit of ointments, balms and patches at all times: While wincing at the stupidity (and it's always something stupid, isn't it?) that left you with an abrasion, contusion or unintended incision, you can draw some comfort in the fact that you were smart enough to bring tools. Here's what to include, as recommended by Eric A. Weiss, M.D., associate professor of medicine at Stanford Medical Center and board member of the Wilderness Medical Society.