Sodium balance during U. S. football training in the heat: cramp-prone vs. reference players.

U. S. football players with a history of heat cramps were evaluated for the effect of physical training, sodium intake, and loss of sweat sodium on whole blood sodium concentration (BNa). Athletes (n=14 males, 24+/-1 y) were recruited and studied based on medical history, age, and position. The reference group (R, n=8 without a cramping history) and cramp-prone group (C, n=6, history of whole-body cramps associated with extensive sweat loss during exercise in the heat) were measured for body mass and BNa (ISTAT) before and after team training of 2.2 h in hot conditions (WBGT=29-32 degrees C). Intake and loss of fluid and sodium were also measured to determine respective acute balance. In R, BNa was stable pre- to post-training (138.9+/-1.8 to 139.0+/-2.0 mmol/L) while it tended to decline in C (137.8+/-2.3 to 135.7+/-4.9 mmol/L), and three subjects in C had BNa values below 135 mmol/L (131.7+/-2.9 mmol/L). C consumed a greater percentage of total fluid as water (p<0.05). Mean sweat sodium concentration was (52.6+/-29.2 mmol/L for C and 38.3+/-18.3 mmol/L for R (p>0.05). Compared to R, C tended to experience a decline in BNa and greater acute sodium imbalance. These changes may place cramp-prone players at greater risks for developing acute sodium deficits during training.

Exercise condition affects hedonic responses to sodium in a sport drink.

We measured the dose-response effects of drink sodium content (treatments: 0 mmol/l, 18 mmol/l, 30 mmol/l, 40 mmol/l, and 60 mmol/l) on sensory perception and palatability in athletes at four time points: in a sedentary laboratory setting (non-exercise context), pre-exercise, and after 60 min and 120 min of aerobic-circuit exercise. Fifty-five triathletes and runners (30 males, 39.7 (8.0 S.D.) years; 25 females, 37.2 (9.2 S.D.) years) sip-tested chilled 6% carbohydrate drinks varying in sodium content during sedentary and pre-exercise conditions and had ad lib access to drinks during exercise conditions. There was a significant intensity discrimination among all sodium levels (p

Effect of exercise and fluid consumption on salivary flow and pH.

Recent claims have been made regarding the putative erosive effects of regularly ingesting low-pH beverages on the integrity of tooth enamel. The purpose of this study was to determine whether fluid consumption during exercise affects the body's defenses against enamel erosion: saliva flow and salivary pH. Males and females (n=50) exercised in the heat (26.7 degrees C, 40 % RH) for 75 min on four occasions. Within each session, subjects consumed ad-lib either water, a sports drink (Gatorade), diluted orange juice, or a homemade sports drink, with the latter three fluids all having low pH values (3.0 to 4.0). Prior to and following exercise, subjects performed a standard stimulated saliva collection procedure. Immediately following collection, saliva flow rate and pH were determined for each sample. Repeated-measures ANOVA were used to evaluate the data. Compared to pre-exercise salivary flow rates (2.6+/- 0.8 ml/min), the post-exercise rate was not different when consuming the sports drink (2.6+/- 0.9 ml/min), but decreased when water or the homemade sports drink was ingested (2.4+/- 0.9 ml/min; p<0.05). A time-by-drink interaction (p<0.05) revealed slight differences in saliva pH after exercise, depending on the beverage consumed; post-exercise saliva pH was highest for water (7.2+/- 0.2) and lowest for the homemade sports drink (7.1+/- 0.2), with the sports drink and diluted orange juice values falling in between. The results suggest that minimal changes occur in saliva pH and the rate of stimulated saliva flow with beverage consumption during exercise. Subsequent research is needed to determine whether maintenance of saliva production by drinking beverages during exercise influences the body's defenses against dental erosion via saliva production.

Physical activity patterns associated with cardiorespiratory fitness and reduced mortality: the Aerobics Center Longitudinal Study.

OBJECTIVES: This study examined cross sectionally the physical activity patterns associated with low, moderate, and high levels of cardiorespiratory fitness. METHODS: Physical activity was assessed by questionnaire in a clinic population of 13,444 men and 3972 women 20 to 87 years of age. Estimated energy expenditure (kcal.wk-1) and volume (min.wk-1) of reported activities were calculated among individuals at low, moderate, and high fitness levels (assessed by maximal exercise tests). RESULTS: Average leisure time energy expenditures of 525 to 1650 kcal.wk-1 for men and 420 to 1260 kcal.wk-1 for women were associated with moderate to high levels of fitness. These levels of energy expenditure can be achieved with a brisk walk of approximately 30 minutes on most days of the week. In fact, men in the moderate and high fitness categories walked between 130 and 138 min.wk-1, and women in these categories walked between 148 and 167 min.wk-1. CONCLUSIONS: Most individuals should be able to achieve these physical activity goals and thus attain a cardiorespiratory fitness level sufficient to result in substantial health benefits.