Sports Fitness Training

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.