Sports Fitness Training

The most accurate method to assess body composition involves chemical analysis of the body. However, as this can be done only after death, it is of limited value in the assessment of body composition in the living. Fortunately, several indirect methods for assessment have been developed for estimation in living subjects. The most common are densitometry (underwater weighing or air displacement), anthropometry (measures of body girths, breaths, and/or skin fold thickness), and bioelectrical impedance (measures of opposition to a weak electrical current introduced into the body). Of these, densitometry is considered the most accurate because its estimation is based on results obtained from direct chemical analysis of cadavers. However, it cannot be exact for given individuals because most will differ somewhat from the cadavers that were analyzed. Consequently, there will always be a small absolute error (perhaps 2-3%) that must be considered when these measures are used. This, of course, is of little concern to your health when relative measures are compared, i.e., in a study in which before and after measures are compared, because the error is constant. Typically, anthropometry and bio-impedance methods involve more absolute error, as their estimations are based on results from densitometric analyses, i.e., they are estimates of an estimate. However, they are widely used because they are easy and the necessary equipment is both portable and relatively inexpensive. Other more sophisticated body composition measures are possible including magnetic resonance imaging and dual energy X-ray absorptiometry but are primarily used in research settings as the equipment necessary is expensive.

In the athlete, it appears that the most promising characteristic of antioxidant supplementation regarding performance is the ability to aid recovery As athletes know, recovery after exercise is vitally important to improved performance. Eccentric contractions (i.e., “negatives”) are a necessary part of many types of sport and result in exaggerated myofibrillar disruption, delayed-onset muscle soreness, inflammation, and reduced force generation. Thus, decreasing muscle damage and inflammation (and/ or hastening a return to “healthy” status) can allow an athlete to resume training and more rapidly improve in ability The response to muscle damage can last several days and is hallmarked by increased muscle enzyme release, urinary nitrogen excretion, increased metabolic rate, and increased cortisol and interleukin concentrations. Subjects also experience decreased glucose tolerance and strength after eccentric exercise This period of eccentric recovery is in stark contrast to the shorter, less traumatic 24-48 hour recovery period observed after less-damaging concentric exercise. As mentioned earlier, circulating leukocytes (white blood cells) infiltrate traumatized muscle tissue and, in concert with cortisol, prostaglandins, and various cytokines, they induce catabolism, edema, pain, and inflammation. Although this immune response is primarily beneficial, the period of catabolism may be unnecessarily aggressive before growth factors are secreted and tissue growth and/or repair begins.Think of this scenario as equivalent to a group of janitors arriving to clean up a mess. But, in addition to cleaning up the original mess, these janitors (neutrophils and monocytes) also tend to tear down the walls as they clean. Antioxidant vitamins like vitamin E and vitamin C may combat this aggressive cleaning strategy of the janitors (part of the acute-phase response) both by buffering the reactive oxygen species that are released and by suppressing cell membrane peroxidation and prostaglandin formation, which is partly responsible for the inflammation. The next logical question would be, Why would anyone punish themselves with eccentric contractions to the point of requiring pharmacologic doses of vitamins The logic behind using repeated, high-intensity eccentric contractions involves the growth response. Because the muscle hypertrophic response is greater, athletes requiring gains in muscular size and/or strength often use negative training using resistance exercises and/ or plyometrics. As we have seen, this can aggravate oxidant insult, inducing damage that might only be treated optimally with antioxidant supplementation

Muscle mass is dramatically reduced in both men and women with advancing age. Called sarcopenia, this phenomenon has considerable significance because it leads to a decreased quality of life, and often, major health care expenses for the associated medical/nursing care. More­over, these costs represent only a fraction of what is likely to come over the next 20-30 years as the post-war baby boom generation enters the age range in which sarcopenia begins to affect them. Clearly, the effects of aging on the body’s ability to respond undoubtedly playa role in this response-it has been reported that myofibrillar protein synthesis is reduced by 30% in individuals over 60 years of age. However, inactivity must always be a factor. Indeed, strength training has been shown to augment muscle function in both men and women even in the lath decade of life. Further, this type of functional improvement is not the result of neurological changes alone as muscle protein synthesis can be increased with 3 months of strength exercise even in frail 76-92-year­old men and women Some data indicate that as little as 10 days of energy and protein supplementation can enhance protein synthesis and fat-free (lean) mass at least in poorly nourished 60-90-year-old men and women. As nutrient intake is frequently less than ideal in the eld­early and energy and macro nutrient needs are increased with strength exercise. It is logical to assume that nutrient supplementation would enhance the response of muscle to strength exercise. One study observed that a supplements containing 60% carbohydrate, 23% fat, and 17% protein (1500 kJ/day) given to year-old men and women who participated in a 10-week strength training program produced significant increases in muscle strength and size than the same training alone. Although increasing dietary protein intake from 0.6 to 1.2 to 2.4 g/kg did not alter myofibrillar protein synthesis in elderly men and women, these data do not necessarily implicate energy as the causative factor because this latter study only involved 1 day of supplementation and a brief (3-day) strength program. Acute versus chronic exercise could be a significant factor in determining nutrient need. Further, length of time on the dietary treatment is likely critical. Finally, at least in older women, there is some evidence that quantity of the protein per intake may affect subsequent protein synthetic rate. Over a 14-day interval in older women (60-73 years), when the protein intake was divided equally into four aliquots fat-free mass gain was significantly less when compared with a situation in which most of the protein was consumed a large bolus However, the bolus protein-feeding pattern had no such effect in younger women. Although clearly more study is necessary before these data can be explained fully, mass of protein consumed and/or timing of intake throughout the day may be critical to the protein synthetic response. Finally, the latter two studies were conducted on sedentary subjects and it is likely that these factors become even more important when combined with chronic strength exercise. Due to the increased requirements of the growth process, protein intake is also important for young children and adolescents. Although not well studied, it is quite likely that regular strength training could lead to even greater requirements in this population. More­over, from a practical perspective, this is likely to be of increasing importance in the future as strength training is becoming more of an essential component of almost all sporting endeavors. For the same reason, women who are pregnant who continue to exercise would be another group likely to benefit from additional dietary protein.

Under normal physiological conditions, cells are highly efficient at maintaining steady state. However, under conditions of physiological stress, such as hypoxia (reduced oxygen supply) caused by ischemia or strenuous exercise, the energy balance can be disrupted and the functional integrity of the cell can be compromised. In these conditions, ATP concentrations fall, which leads to increases in ADP and AMP levels. In an attempt to maintain energy balance the first response of both heart and skeletal muscle cells is to break down AMP, leading to an increase in cellular IMP concentration. If ATP use continues to exceed the rate of regeneration, energy charge is further depressed. The ultimate result is catabolism of IMP to inosine and then hypoxanthine, and AMP to adenine. Hypoxanthine and adenine are lost from the cell and the concentration of total adenine nucleotides is depressed. As such, a fall in energy charge below physiological limits of the cell is prevented and it takes several days for the concentration of adenine nucleotides to return to normal.

How Women Respond to Exercise

Despite the popularity of strength training and flexibility among women in recent years, there has been little scientific study of specifically how women respond to this type of exercise. With endurance exercise, some data suggest that women use less protein for energy than men perhaps as a result of differences in fat use induced by gender-specific hormonal responses. Rodent data indicate that estradiol is protective for muscle cell membranes and, consequently, part of this response may be due to less exercise­induced damage to the muscle membrane in women. Moreover, there is some evidence that protein need with endurance exercise may even vary across the menstrual cycle Unfortunately, the effects of strength training on protein requirements in females have not been investigated extensively. Based on the observed gender differences in metabolism and the known differences in hormonal responses, it is quite possible that women respond to strength exercise somewhat differently than men. As a result, detailed study of how strength exercise training is influenced by dietary protein in women is needed.