This study examined the question of whether increases in plasma volume (hypervolemia) induced through exercise affect muscle substrate utilization and muscle bioenergetics during prolonged heavy effort. Six untrained males (19-24 yr) were studied before and after 3 consecutive days of cycling (2 h/day at 65% of peak O2 consumption) performed in a cool environment (22-23 degrees C, 25-35% relative humidity). This protocol resulted in a 21.2% increase in plasma volume (P less than 0.05). During exercise no difference was found in the blood concentrations of glucose, lactate, and plasma free fatty acids at either 30, 60, 90, or 120 min of exercise before and after the hypervolemia. In contrast, blood alanine was higher (P less than 0.05) during both rest and exercise with hypervolemia. Measurement of muscle samples extracted by biopsy from the vastus lateralis muscle at rest and at 60 and 120 min of exercise indicated no effect of training on high-energy phosphate metabolism (ATP, ADP, creatine phosphate, creatine) or on selected glycolytic intermediate concentrations (glucose 1-phosphate, glucose 6-phosphate, fructose 6-phosphate, lactate). In contrast, training resulted in higher (P less than 0.05) muscle glucose and muscle glycogen concentrations. These changes were accompanied by blunting of the exercise-induced increase (P less than 0.05) in both blood epinephrine and norepinephrine concentrations. Plasma glucagon and serum insulin were not affected by the training. The results indicate that exercise-induced hypervolemia did not alter muscle energy homeostasis. The reduction in muscle glycogen utilization appears to be an early adaptive response to training mediated either by an increase in blood glucose utilization or a decrease in anaerobic glycolysis.
SummaryIn a prospective study, 110 eligible patients (111 eyes) were randomly selected to have contact lenses for aphakia (CL). The lens of first choice was a daily-wear hard (DWH) PMMA contact lens. Extended-wear (XW) lenses were fitted to those who failed with DWH lenses. The numbers in the two groups were approximately equal.Eighty per cent of eyes were successfully wearing CLs six months post-operatively and 72% were still wearing them after five years.The mean age of both groups of patients was greater than 70 years but the DWH group was significantly younger (p
An experimental method is presented, for the study of glow discharges, that can provide data suitable for analysis in terms of the diffusion of a ternary mixture. Particular emphasis is given to the constriction of flow discharges in neon with increasing gas density. It is found that quantitative estimates of the onset of this phenomenon are now possible.
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