This is an excerpt from Soccer Anatomy by Donald T. Kirkendall.
Injuries are a part of all sports. The most common soccer injury is a contusion (bruise) when you get kicked, fall, or bumped. The most common location is the lower extremity, mostly between the knee and ankle. Most leg contusions do not cause a player to miss much training time or competition. The top four time-loss soccer injuries are ankle sprains, knee sprains, hamstring strains, and groin strains. In elite soccer, hamstring strains are most common. At lower levels of play, ankle sprains are number one.
There are some gender differences. Females have a higher rate of injury to the anterior cruciate ligament of the knee. Newer data suggest that females suffer more concussions than do males. The difference in concussion rates may be real, or it could be skewed because women tend to be more forthcoming than men about head injuries.
Good prevention programs, when substituted for a traditional warm-up, have been shown to reduce common injuries by about one-third. FIFA presents an excellent graduated warm-up (The 11+). For players and teams with a special concern about hamstring strains, pay close attention to the hamstrings exercise and the balance exercises. These have been shown to reduce hamstring strains. The key to any injury prevention program is compliance. Programs such as The 11+ are not an occasional diversion. Players must complete these programs at every training session and do a shorter version before competition.
For many countries in the northern hemisphere, soccer is a fall to spring sport; summer is the off-season. In the United States, the professional game parallels the baseball season, making it a spring to fall sport. Depending on the time of year, soccer in the southern states can be played in pretty oppressive conditions. All summer leagues and tournaments need to have a plan in place to handle players suffering from heat illnesses. Players who succumb to the heat may initially show minor symptoms such as heat cramps, but problems can rapidly progress to far more serious issues such as heat exhaustion and heatstroke, which is a potentially fatal collapse of the body's ability to control its temperature. You may have read about heat-related deaths in American football players.
The body loses heat by radiation through radiant loss of heat through heat waves; convection (like standing in front of a fan or air conditioner); conduction, which is direct contact with a cooler surface (like placing an ice-cold towel on the head); or evaporation, which is the most important mechanism during exercise. Sweat production is not the loss of heat; the evaporation of the sweat results in heat loss. Any barrier to heat loss will slow the rate of evaporation. Two barriers frequently encountered in soccer include clothing, especially dark clothing that covers much of the body, and humidity. Today's sports clothing is designed to aid evaporation.
Whenever matches are scheduled during hot and humid weather, put strategies in place for making fluids available. Many youth leagues, particularly in the south, have water breaks in each half as part of the rules. If water breaks are not part of the rules, the coaches can approach the referee and ask for a break if the conditions warrant it. The referee has this authority and would probably appreciate the break as well. During the men's gold medal match at the Beijing Olympics, a water break was included in each half because of the conditions.
A good definition of fatigue is the failure to maintain an expected power output—you want to run fast but are unable to. Fatigue can be both general and temporary and can come from a number of mechanisms. For example, to run fast, you need muscle glycogen. When muscle glycogen levels decline below set levels, you walk. Increasing muscle glycogen stores through training and proper food selection will delay fatigue and allow you to go deeper into the match before tiring. In addition, an ample store of glucose ensures that the brain has a ready supply of the only fuel it can use. The brain can become fatigued, too. Elevated body temperature and the accompanying loss of fluids by evaporation are also factors in general fatigue. Because body temperature affects performance, it is necessary to keep fluid levels up so the body can produce sweat for evaporation and heat loss. Drink often.
Temporary fatigue is a result of rapidly altered and remedied local muscle chemistry that affects the ability of the muscle fibers to contract. Lactic acid contributes to temporary fatigue. After a few repeated fast runs, you tire, but in a few minutes you can be back and ready to go again. Any improvement in aerobic capacity will let you do more, or longer, hard runs before temporary fatigue sets in by improving your ability to recover more quickly. Training for rapid recovery minimizes the effects of temporary fatigue by speeding up the removal of lactic acid and the recovery of processes that couple the processes associated with excitation of the muscle with the muscle's ability to contract.
Read more from Soccer Anatomy by Donald T. Kirkendall.