Eating for Endurance or Ultraendurance.

In brief For optimum endurance, people who or compete must meet JMMJ basic nutrition requirements. Endurance and ultraendurance athletes need high carbohydrate intake to meet energy needs, as well as consistent intake of protein, vitamins, and minerals. Meeting these nutrient needs can be difficult, but through careful planning and monitoring of training schedules, body weight, and food and liquid intake, the athlete can develop a diet that meets the demands of both sport and life-style.

Nutrition for a Cold Environment.

In brief: Preventing hypothermia is crucial to those who work or spend recreation time in cold environments. Adequate energy from the correct proportion of carbohydrates, fats, and proteins can help. Vitamins and minerals are also necessary to prevent nutrition deficiencies and impaired function, but there is no evidence to suggest an increased requirement for them is attributable to cold exposure alone. High protein diets appear to be the worst choice for cold weather work; compared with diets high in carbohydrates or fats, high protein diets increase metabolic water requirements and reduce cold tolerance.

Sports Nutrition for the Primary Care Physician: The Importance of Carbohydrate.

In brief: Proper nutrition is basic to an athlete's performance. It is inextricably tied to maximum training, endurance, delay of fatigue, and recovery. Working muscles need carbohydrate fuel; the optimal diet for an athlete is a regimen of adequate calories, high carbohydrate, and low fat. Many athletes, however, do not appreciate the number of calories needed to support their athletic activity and do not meet their energy needs. Timing of nutrition is also crucial to optimal performance. Athletes need to consume a balanced diet and adequate carbohydrate calories during training, before and during competition, and immediately afterward.

Nutritional conditioning for athletic competition.

Diet in itself cannot provide fitness or championship form, but a poor diet can ruin both. Optimal nutrition is a basic component of training that is necessary for the development and maintenance of top physical performance. Appropriate application of recent research findings can have a beneficial impact on exercise performance.

Salicylic acid stimulation of palmitic acid oxidation by rat skeletal muscle mitochondria.

The effects of salicylic acid on palmitic acid oxidation were studied using rat skeletal muscle mitochondria. Salicylic acid, in concentrations that exerted no effect on mitochondrial coupling (0.1 mM), significantly stimulated mitochondrial palmitic acid oxidation, with maximal stimulation occurring at subsaturating concentrations of substrate. In the same preparation, salicylate had no effect on the oxidation of palmitoylcarnitine or palmitoyl-CoA. Salicylate appears to augment the initial step of palmitic acid oxidation by lowering the apparent Michaelis constant (Km) of long chain fatty acid: CoASH ligase (AMP) (EC 6.2.1.3) for palmitic acid.

Observations on preadipocytes and their distribution patterns in rat adipose tissue.

Microscopic examination of adipocytes isolated from adult rat epididymal adipose tissue revealed numerous small cells (less than 10 micron) morphologically similar to larger adipocytes. These small adipocytes appear identical to a new classification of adipose cells termed preadipocytes. Electron micrographs of these preadipocytes revealed examples of cells less than 10 micron in diameter in various stages of maturation and lipid accumulation. The percent distribution pattern of these small adipocytes was not significantly altered by exercise although exercise shifted the distribution patterns of the larger cells (greater than 30 micron) toward a smaller mean cell size. The quantitative significance of preadipocytes is not established but these preliminary observations indicate that adipocytes less than micron in diameter may account for a numerically greater proportion of the total adipocytes observed in collagenase isolated preparations than heretofore recognized, although their contribution to total adipose mass is probably negligible.

The influence of exercise and diet on myoglobin and metmyoglobin reductase in the rat.

This study was designed to evaluate the influence of exercise and diet on selected aspects of heme protein metabolism in the rat. Two levels of treadmill exercise and three levels of dietary restriction were imposed on growing male rats over a 12-week experimental period. Neither training nor diet had any effect on erythrocyte NADH-MetHB reductase. The group undergoing the highest level of treadmill exercise had a significantly lower HB concentration. The activity of NADH-MetMB reductase was increased in the group undergoing the highest level of training and decreased in the groups whose diet was restricted by 25% and 35%. These changes were seen only in the soleus muscle. Other muscles, including the heart, psoas, and quadriceps were unaffected by either exercise of diet. Both levels of exercise were effective in increasing muscle MB concentration, but only in the quadriceps and soleus muscles. These data illustrate the adaptive nature of muscle MB and NADH-MetMB reductase. They also illustrate the different adaptive patterns of these two components of muscle.

Cyclic AMP metabolism in adipose tissue of exercise-trained rats.

Cyclic AMP metabolism in epididymal adipose tissue of exercise-trained rats was examined to determine if training induced changes in cyclic AMP production or inactivation. Beginning at 7 weeks of age, male rats were physically trained by 12 weeks of treadmill running. Pair-fed control rats remained sedentary in their cages for the duration of the experiment. Tissue levels of cyclic AMP were measured in epididymal adipose tissue slices incubated with norepinephrine. Adenyl cyclase was assayed in adipocyte ghost cell prepartions and low-Km phosphodiesterase was assayed in homogenates of adipose tissue. In response to norepinephrine stimulation, tissue cyclic AMP levels were reduced in trained compared to untrained rats. Training increased the ratio of activity of phosphodiesterase relative to adenyl cyclase. The results of this study indicate that cyclic AMP production in response to norepinephrine stimulation is not increased by training and may even be reduced, implying that adipose tissue cyclic AMP levels may be under a greater degree of control in trained rats. Modulation of adipose tissue cyclic AMP levels may function to regulate more closely the duration of lipolysis in exercise-trained rats.

Adaptation of protein metabolism to endurance training. Increased amino acid oxidation in response to training.

This study was conducted to investigate alterations in excretion of urea and total nitrogen after6-8 weeks of daily exercise and to establish if the capacity for amino acid oxidation in muscle is influenced by endurance training. Urea nitrogen excretion was increased in trained compared with untrained rats and nitrogen balance was less positive in trained than in untrained rats. Increased [14C]leucine oxidation with training was observed both in vivo and in vitro. The results of this study demonstrate that amino acid catabolism is increased during exercise training and that the muscle enzymes involved in leucine oxidation adapt to endurance training in a manner similar to the enzymes of carbohydrate and fat catabolism.

Dietary carnitine and adipose tissue turnover rate in exercise trained rats.

Rats trained by 12 weeks of treadmill running were divided into two groups and fed a control diet or an identical diet supplemented with 0.5% L-carnitine. Adipose tissue fatty acid turnover was subsequently estimated by an odd-carbon fatty acid enrichment method utilizing undecanoate as a marker representative of adipose tissue fatty acids. Compared to sedentary untrained control rats, exercise training increased perirenal adipose tissue turnover rate approximately 70%. Trained rats fed the carnitine supplemented diet did not exhibit any further increase in turnover rate. Neither [1-14C]palmitate oxidation by skeletal muscle homogenates nor palmitycarnitine acyl-transferase activity in skeletal muscle mitochondria was affected by carnitine feeding. The results of this study indicate that exercise training increases the turnover rate of adipose tissue fatty acids, but supplemental dietary carnitine does not. Under the conditions of this study, endogenous skeletal muscle carnitine levels in trained rats appear to be adequate to support the rate of fatty acids oxidation incurred by daily treadmill running.

Adipose tissue cell size and lipolysis in the rat: response to exercise intensity and food restriction.

This experiment was designed to determine if the adaptive increase in adipose tissue epinephrine-stimulated lipolysis (ESL) observed in exercise trained rats is related to decreased adipocyte size or a direct response to exercise. Two levels of treadmill exercise and three levels of food restriction were imposed on male rats over a 12 week experimental period to create a distribution of adipose tissue cell sizes. Epinephrine-stimulated lipolysis was subsequently measured in the isolated adipocytes from rats trained at two different exercise levels and in untrained rats fed either ad libitum or 16%, 27%, or 35% dietary restriction. Energy restriction was effective in reducing body weight and to some extent epididymal fat pad weight; however, adipocyte size and number were not significantly affected. Exercise in both groups of trained rats was effective in reducing adipocyte size; however, cell size did not differ between training groups. The group receiving the greatest amount of daily exercise had significantly greater ESL indicating that the adaptive increase in lipolytic potential seen in adipose tissue of exercise trained rats is a true metabolic adaptation not secondary to reduced cell size.

Adipose tissue cellularity and lipolysis. Response to exercise and cortisol treatment.

Male rats a 5 wk of age were subjected to 13 wk of intensive treadmill running to study the effect of exercise on adipose tissue cellularity and lipolysis. Untrained controls of the same age remained sedentary in their cages for the duration of the experiment. Adipocyte numbers were similar in eqidiymal fat pads from trained and untrained rats (12.7 plus or minus 1.3 X 10(6) vs. 15.3 plus or minus 1.3 X 10(6) cells/pad), however trained rats had smaller fat pads containing smaller cells (0.09 plus of minus 0.01 vs. 0.20 plus or minus 0.04 mug triglyceride/cell). Adipocytes from trained rats possessed greater epinephrine-sensitive lipase activity than sedentary rats on a per cell, per milligram protein, per gram adipose tissue, or per fat pad basis. Although the smaller cells of the trained rats had greater epinephrine-sensitive lipase activity than the larger cells of the untrained rats, lipolysis was positively correlated with cell size within both treatment groups. Cortisol treatment of intact animals did not significantly affect in vitro adipose tissue lipolysis. The results of this study indicate that exercise training increased the potential of adipose tissue cells to release free fatty acids in response to epinephrine stimulation. Exercise training initiated at 5 wk of age had only a small effect on adipose tissue cell numbers but significantly decreased cell size.