Water versus carbohydrate-electrolyte ingestion before and during a 15-km run in the heat.

Twelve highly trained male runners ran 15 km at self-selected pace on a treadmill in warm conditions to demonstrate differences in physiological responses, fluid preferences, and performance when ingesting sports drinks or plain water before and during exercise. One hour prior to the start of running, an equal volume (1,000 ml) of either water or a 6% or an 8% carbohydrate-electrolyte (CE) drink was ingested. Blood glucose was significantly higher 30 min following ingestion of 6% and 8% CE compared to water, significantly lower at 60 min postingestion with both sports drinks than with water, but similar after 7.5 km of the run for all beverages. During the first 13.4 km, oxygen uptake and run times were not different between trials; however, the final 1.6-km performance run was faster with both CE drinks compared to water. Despite a lower preexercise blood glucose, CE consumption prior to and during exercise significantly improved performance in last 1.6 km of a 15-km run compared to water.

Fluid intake in male and female runners during a 40-km field run in the heat.

To compare physiological responses, hydration status and exercise performance in similarly trained men and women in a hot, humid environment, 12 highly trained runners were studied during a simulated 40-km race. A 7% carbohydrate-electrolyte (CE) beverage was consumed prior to exercise (400 ml) and every 5 km (approximately 250 ml) during the run. The run times of the males and females did not differ significantly (173.5 +/- 8.5 and 183.8 +/- 4.2 min, respectively); nor did the rate of fluid intake relative to body mass (10.3 +/- 0.7 and 10.7 +/- 0.8 ml kg-1 h-1, respectively) or percent body mass loss (4.0 +/- 0.1% and 3.9 +/- 0.1%, respectively). During the run, %VO2 max, heart rate, concentrations of blood lactate, serum total protein and plasma osmolality were also similar for both groups. However, some significant sex differences (P < 0.05) were observed: the females had lower plasma volume losses and higher serum potassium and sodium concentrations than the males during the run. Rectal temperatures were lower in the female runners compared with the males during the last 10 km of the run (0.7 degrees C) and recovery (1.1 degrees C). Findings from this 40-km field run in hot, humid conditions suggest that CE fluid replacement at a relatively similar dosage (approximately 10 ml kg-1 h-1) may have sex-specific physiological effects. These observations warrant further investigation to assess the need for sex-specific fluid replacement guidelines.

Validation of the 12-minute swim as a field test of peak aerobic power in young women.

The purposes of this study were to validate the 12-min swim as a field test of VO2 peak in female recreational swimmers and to compare its validity with that of the 12-min run. The results are contrasted with those previously reported on a comparable group of male recreational swimmers. Thirty-four young women completed 12-min swim, 12-min run, tethered swimming VO2 peak, and treadmill running VO2 peak tests within 3 weeks. Mean (+/- SD) 12-min swim and run distances were 597 +/- 82 and 2,313 +/- 317 m, and mean tethered swim and treadmill run VO2 peak values were 39.2 +/- 4.9 and 45.4 +/- 6.3 ml.kg BW-1.min-1, respectively. Correlation coefficients and standard errors of estimate for predictions of swimming VO2 peak from the 12-min swim (.42 and 4.5 ml.kg BW-1.min-1) and run (.58 and 4.1 ml.kg BW-1.min-1) and for predictions of treadmill run VO2 peak from the 12-min swim (.34 and 6.0 ml.kg BW-1.min-1) and run (.87 and 3.2 ml.kg BW-1.min-1) indicated that the 12-min run was a more accurate predictor of tethered swim or treadmill run VO2 peak than the 12-min swim. These data are in close agreement with our previous study on young male recreational swimmers. We conclude that the 12-min swim has relatively low validity as a field test of peak aerobic power and that it is not an equally valid alternative to the 12-min run in young adult female recreational swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a new magnetic resonance imaging method for quantitating adipose tissue areas.

We have developed a new magnetic resonance imaging (MRI) protocol to quantitate intraabdominal and subcutaneous fat and have validated it by comparing measurements of fat areas by MRI with those obtained by computed tomography (CT) in 11 asymptomatic volunteers who all had a single CT and MRI image taken at the level of the umbilicus. The new MRI protocol was based on a water-fat separation method by which the slice selection routines excite water and fat protons in different positions along the slice select direction. This method performed more reliably than earlier methods based on phase differences between water and fat signals. Fat areas measured by MRI exceeded those measured by CT by 8-22 percent, and fat areas and ratios obtained by MRI correlated well with CT (r = 0.98 for areas and, for ratios, r = 0.81). The ratio of intraabdominal/subcutaneous fat measured by MRI in seven males was significantly greater than that in four females. We also compared the new method with a previously published inversion recovery (IR) method in seven additional volunteers. Agreement between the two methods was excellent, and the major differences were technical: the IR protocol produced images that may require custom image processing programs when obtained on some scanners. Comparability of the two methods provides further reassurance of the validity of both. MRI presents an attractive opportunity for directly measuring intraabdominal fat in order to correlate this with metabolic parameters and to visualize changes during weight loss.

Carbohydrate-electrolyte replacement during a simulated triathlon in the heat.

Effects of a 7% carbohydrate-electrolyte drink (CE) or a flavored water placebo (P) on physiological function and performance were compared during a simulated triathlon (ST) in the heat. Ten trained male triathletes performed two STs, consisting of 1.5 km swimming, 40 km cycling, and 10 km running in an environmentally controlled area at self-selected race pace. Subjects consumed 2 ml.kg-1 (130-174 ml) of CE or P following the swim, at 8.0-km intervals during cycling, and at 3.2-km intervals during running. Sweat rate, rectal and mean skin temperatures, perceived exertion, heart rate, plasma osmolality, percent change in plasma volume, total protein, Na+, K+, and lactate were similar during the ST under both drink conditions, but RER and plasma glucose were higher (P less than 0.05) with CE. During the last 4 km of running, VO2 was significantly higher with CE. Mean run time and total ST time were faster with CE (by 1.4 and 1.2 min) although not significantly different (P less than 0.06 and P less than 0.10) from P. Subjects reported no significant difference in nausea, fullness, or stomach upset with CE compared to P. General physiological responses were similar for each drink during 2 h of multi-modal exercise in the heat; however, blood glucose, carbohydrate utilization, and exercise intensity at the end of a ST may be increased with CE fluid replacement.

Occupational burnout among correctional health workers. Perceived levels of stress and social support.

1. Approximately one third of the sample study fit Maslach's burnout profile, with low personal accomplishment, high depersonalization, and high emotional exhaustion. Perceived stress was a significant predictor of the sense of personal accomplishment and emotional exhaustion. 2. Both male and female subjects had low to moderate mean scores on the social support scale. Social support as measured in this study was limited to that received from coworkers and supervisors. 3. The results of this study point to a need for intervention in this setting. Specific interventions for decreasing stress and thus decreasing chances for burnout are discussed. 4. The development of a broad employee health care program is an example of a primary prevention intervention to decrease stress in this setting. Such a program would include instruction in methods of stress reduction and stress management, including exercise and relaxation techniques.