The principles of sports physiology outline the underlying mechanisms that help to bring about a healthy transition from a not-so-healthy state. The life practice of regular exercise, healthy diet and relaxation creates benefits that can be seen and felt quickly!
By putting in an effort for regular exercise, the person without illness is rapidly rewarded by an increase in overall well-being and stamina. The same principles apply to men and women; although differences in body size, composition and hormones influence athletic performance.
Men benefit from the anabolic effect of testosterone produced by male testicles. It gives substantially greater muscle size and therefore strength to male, compared with female, muscles.
Sometimes women have been shown to have greater athletic endurance due to increased body fat. The female sex hormone, estrogen, is known to increase fatty deposits in the breast, hips and subcutaneous tissues of the female. On average, the non-athletic female has a substantially larger percentage of body fat compared to the non-athletic male who, through the influence of testosterone, will have considerably more muscle than the non-athletic female and considerably more strength as a consequence. It is clear that males may perform better than females in contests requiring straightforward muscle strength and speed, whereas increased fatty deposits may supply energy in long tests of endurance for females.
Another influence on performance differences comes from the differing effects of the sex hormones. Testosterone is associated with aggression and competitive drive, in contrast to the calming influence of estrogen. When a person is exercising, the strength, power and endurance of muscles determine the performance. In general, a person with more testosterone and therefore, more muscle, will have greater strength. However, exercise training programs facilitate increased muscle strength. The holding strength of a muscle has implications for performance as well as injury, as stretching an already contracted muscle can lead to internal tearing. The power of a muscle determines how much it can do in a given period of time, whereas endurance depends to a large extent on nutrition that supports a person's effort. A high-carbohydrate intake allows for the availability of glycogen to the muscles, and therefore, a greatly improved performance compared to that allowed by a mixed or high fat diet.
Different muscle metabolic systems are utilized depending upon the type of exercise performed. A system called the Phosphagen System is used for short bursts of muscle power, such as jumping and football dashes. This complex system involves the metabolism of adenosine triphosphate, the basic source of energy for muscle contraction. The Glycogen-Lactic Acid Systemprovides energy over a longer time span.
The first stage of the processing of glycogen takes place without oxygen, when each glucose molecule is split into two pyruvic acid molecules. Adequate oxygen intake is needed for the second stage of the processing of glucose from glycogen; otherwise the pyruvic acid is converted into lactic acid, resulting in severe muscle spasm and fatigue. TheGlycogen-Lactic Acid Systemsupplements the performance of thePhosphagen Systemto sustain performance over intermediate muscle activity such as that required in playing basketball. TheAerobic Systemrequires the oxidation of nutrients to supply energy and helps to sustain performance over time as long as the nutrients are available. This system provides the resources required over long distances and time spans such as marathon running and jogging and is supplemented by theGlycogen-Lactic Acid Systemwhen more power is required such as in rowing or long swims. The type and duration of the exercise will determine which system or combination of systems will be activated the most frequently.
While the body utilizes both carbohydrate and fat in exercise, a high carbohydrate diet and adequate muscle glycogen are required for optimal athletic performance. A high carbohydrate intake and avoiding tiring exercise beforehand facilitates better recovery after heavy exercise. Similarly, to avoid excess fatigue in training, it is useful to be aware that when training for muscle building, muscle strength increases about 30 percent during the first six to eight weeks of training but not much more after that.
Different people are suited to different types of athletic performance because of their genetic inheritance of their muscle type -- having relatively more fast or slow twitch muscle fibers. Fast twitch muscles are larger in diameter and deliver more power over a shorter time span. Slow twitch fibers are primarily for endurance. Training does not alter percentage of fast or slow twitch type fibers so people are inherently geared to different types of performance. Slow twitch types are better suited to endurance than fast twitch types who are better suited for fast sprints and jumps.
The heart's ability to pump blood to the muscles is the most limiting factor in exercise, while oxygen consumption is a vital factor in endurance performance. The rate of oxygen usage under maximal aerobic metabolism is expressed as VO2Max, which for people who are marathon runners, is nearly twice as much as that in the untrained person. This is partly determined genetically by chest size in proportion to body size, as well as strength of respiratory muscles. The rate at which oxygen can diffuse from the alveoli into the blood differs in different types of sports people. Those who have greater oxygen requirement per minute have greater diffusing capacity; oarsmen have nearly four times the capacity of non-athletes at rest. It is thought that this might be improved by training. Also, people select themselves into those activities for which they are most suited.
There is a direct relationship between work output, oxygen consumption and cardiac output during exercise. The untrained person can increase cardiac output about two thirds of the output of a trained athlete, although resting output is the same in each. The heart enlarges in athletes who perform endurance sports such as marathon runners who achieve a higher maximal cardiac output, perhaps 40% greater than the untrained male. This gives a distinct performance advantage, as it is the ability of the heart to deliver blood, and therefore oxygen, to the muscles that will ultimately determine endurance performance ability.
Many people take up a sport for health and recreation reasons rather than for competition. Adequate and optimal diet, incorporating carbohydrates of the right type, especially pasta and rice, with plenty of good quality drinking water helps to facilitate good recovery from exercise and to prevent dehydration, a cause of sudden death if not recognized early.
Rest and adequate sleep are vital. Without these, the sports person can become vulnerable to muscle strain and other injuries.
The correct clothing for the sport selected is essential as is the preservation of body heat in cold conditions. However, the recognition of the possibility of heat stroke in warm conditions is especially important in order to prevent exhaustion and possible death. The body loses its ability to reduce its temperature if the temperature has over-elevated. This latter situation brings about significantly over-activated intracellular chemical reactions producing yet more heat. This can occur in either very hot or humid conditions or when wearing the wrong clothing which allows excess body heat to build up to the point where tissue and brain cells become destroyed, leading to weakness, dizziness, collapse and unconsciousness. Thus, it is obvious that when undergoing training for any type of sport, however gentle, certain elements need to be built in to ensure safety.
The benefits of regular exercise are indicated by improved well-being, better overall health, improved sleep and immune system function, reduced frequency of illness and better day-to-day function, performance and quality of life. With care and planning, exercise adds a new and vital dimension to healthier living.
Reference
Guyton, A.C. (1992).Human Physiology and Mechanisms of Disease, 5th ed. Philadelphia: W.B.Saunders.
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