Raymond D. Starling

The Effect of volume ingested on rehydration and gastric emptying following exercise-induced dehydration

The purpose of this study was to examine the effects of different drink volumes on rehydration, gastric emptying, and markers of fluid balance following exercise-induced dehydration. Nine male subjects (27.3 +/- 5.47 yr of age, 77.8 +/- 7.9 kg) exercised for 90 min (or until 2.5% of initial body weight was lost) on a cycle ergometer in a hot environment (30 degrees C with 60% RH). Following exercise, subjects were moved to a neutral environment (23 degrees C 50% RH) and rested for 30 min prior to beginning a 3-h rehydration period. During rehydration, subjects were serially fed with an electrolyte solution (14.98 mmol.l-1 Na+, 13.51 mmol.l-1 Cl-, and 7.95 mmol.l-1 K+) every 30 min with either 100% or 150% of the fluid lost during exercise. Gastric contents were determined every 15 min using double sampling. Blood samples, urine samples, and body weights were taken before and after exercise and at 1-h intervals throughout rehydration. Blood samples were analyzed for percent change in plasma volume, electrolyte concentration, aldosterone levels, and renin activity. Urine electrolyte concentrations were also measured. The final percent rehydration was 48.11 and 67.90 for the 100% and 150% conditions, respectively. During rehydration, the subjects emptied 98.9 and 86.0% of the fluid ingested, and the % emptied and used for weight gain at the end of rehydration was 55.1 and 54.6 for the 100% and 150% trials, respectively. Urine production was significantly higher in the 150 compared with the 100% condition while renin and aldosterone levels did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperthermia during Olympic triathlon : influence of body heat storage during the swimming stage

The purpose of this project was to determine whether mild heat stress induced by wearing a wet suit while swimming in relatively warm water (25.4 +/- 0.1 degrees C) increases the risk of heat injury during the cycling and running stages of an International distance triathlon in a hot and humid environment (32 degrees C and 65% RH). Five male triathletes randomly completed two simulated triathlons (swim = 30 min; bike = 40 km; run = 10 km) in the laboratory using a swimming flume, cycle ergometer, and running treadmill. In both trials, all conditions were identical, except for the swimming portion in which a neoprene wet suit was worn during one trial (WS) and a swimming suit during the other (SS). The swim portion consisted of a 30-min standardized swim in which oxygen consumption (VO2) was replicated, regardless of WS or SS. During the cycling and running stages, however, the subjects were asked to complete the distances as fast as possible. Core temperature (Tc) was not significantly different between the SS and WS trials at any time point during the triathlon. However, mean skin temperature (Tsk) and mean body temperature (Tb) were higher (P < 0.05) in the WS at 15 (Tsk = +4.1 degrees C, Tb = +1.5 degrees C) and 30 min (Tsk = +4 degrees C, Tb = +1.6 degrees C) of the swim. These Tsk and Tb differences were eliminated by 15 min of the cycling stage and remained similar (P > 0.05) through the end of the triathlon. Moreover, there were no differences (P > 0.05) in VO2, heart rate (HR), rating of perceived exertion (RPE), or thermal sensation (TS) between the WS and SS. Additionally, no significant differences were found in cycling (SS = 1:14:46 +/- 2:48 vs WS = 1:14:37 +/- 2:54 min), running (SS = 55:40 +/- 1:49 vs WS = 57:20 +/- 4:00 min), or total triathlon times (SS = 2:40:26 +/- 1:58 vs WS = 2:41:57 +/- 1:37 min). These data indicate that wearing a wet suit during the swimming stage of an international distance triathlon in 25.4 degrees C water does not adversely affect the thermoregulatory responses of the triathlete on the subsequent cycling and running stages.

Effect of swimming suit design on the energy demands of swimming.

Eight competitive male swimmers completed a standardized 365.8 m (400 yd) freestyle swimming trial at a fixed pace (approximately 90% of maximal effort) while wearing a torso swim suit (TOR) or a standard racing suit (STD). Oxygen uptake (VO2), blood lactate, heart rate (HR), and distance per stroke (DPS) measurements were obtained. In addition, a video-computer system was used to collect velocity data during a prone underwater glide following a maximal leg push-off from the side of the pool while wearing the TOR and STD suits. These data were used to calculate the total distance covered during the glides. VO2 (3.76 +/- 0.16 vs 3.92 +/- 0.18 l.min-1) and lactate (8.08 +/- 0.53 vs, 9.66 +/- 0.66 mM) were significantly (P < 0.05) lower during the TOR trial than the STD trial. HR was not different (P > 0.05) between the TOR (170.1 +/- 5.1 b.min-1) and STD (173.5 +/- 5.7 b.min-1) trials. DPS was significantly greater during the TOR (2.70 +/- 0.066 m.stroke-1) versus STD (2.58 +/- 0.054 m.stroke-1) trial. A significantly greater total distance was covered during the prone glide while wearing the TOR (2.05 +/- 0.067 m) compared to the STD (2.00 +/- 0.080 m) suit. These findings demonstrate that a specially designed torso suit reduces the energy demand of swimming compared to a standard racing suit which may be due to a reduction in body drag.

Thermal responses to swimming in three water temperatures: influence of a wet suit.

The primary objective of this investigation was to determine the thermal and metabolic effects of wearing a rubberized wet suit (WS) while swimming for 30 min in 20.1, 22.7, and 25.6 degrees C water. Metabolic and body temperature measurements were recorded in each water temperature with subjects wearing either a WS or a competitive swimming suit (SS). Immediately after each swim the subjects cycled for 15 min on a stationary cycle ergometer. Energy expenditure (VO2), heart rate, post-swim blood lactate, work completed on the cycle ergometer, and rating of perceived exertion (RPE) were similar in all trials. Mean (+/- SE) core temperature (Tc) during swimming in the SS trials increased 0.56 (+/- 0.33), 0.48 (+/- 0.20), and 1.22 (+/- 0.24) degrees C, whereas in the WS trial Tc rose 0.62 (+/- 0.22), 1.02 (+/- 0.15), and 0.89 (+/- 0.13) degrees C in the 20.1, 22.7, and 25.6 degrees C treatments, respectively. Following swimming many of the subjects experienced a decrease in Tc, but it was significantly elevated above preimmersion by the end of cycling in all trials except the SS 20.1 degrees C trial. Mean trunk temperatures (Ttr) during swimming in the WS trials were 4.32 +/- 0.16 (20.1 degrees C), 3.90 +/- 0.25 (22.7 degrees C), and 3.21 +/- 0.20 (25.6 degrees C) degrees C warmer than in the SS. Ttr rose after the subjects exited the water, but remained significantly below baseline throughout cycling in all trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Therapy for Obesity in the Elderly

SummaryThe prevalence of obesity is increasing rapidly in the US and other developed countries. Even though the percentage of older individuals is increasing worldwide, obesity has only recently become a recognised problem in this population. Obesity occurs when energy intake chronically exceeds energy expenditure. Moreover, advancing age is associated with an inability to couple energy intake with energy expenditure. Obesity contributes to many adverse health outcomes, including non-insulin-dependent (type II) diabetes mellitus, as well as to an increase in both cardiovascular and all-cause mortality. Only recently has the medical community begun to accept obesity as a disease with a multifactorial pathogenesis that requires systematic lifestyle changes and pharmacological treatment.Several groups of drugs are available for the pharmacotherapy of obesity: anorectic medications (e.g. fenfluramine, dexfenfluramine); substances affectingenergy expenditure and body composition [e.g. chromium (chromium picolinate), ephedrine, anabolic steroids, β3-adrenoceptor agonists]; and drugs affecting the absorption of nutrients (e.g. orlistat). To date, few drugs have produced and sustained a significant bodyweight loss. However, some drugs induce a significant short term reduction in bodyweight compared with placebo. Moreover, there is a paucity of information regarding the effectiveness of these drugs in the treatment of obesity in the elderly. Furthermore, it is even debated whether obesity should be treated with drug intervention in the elderly.Clinicians prescribing medications for obesity treatment in the elderly need to carefully consider the benefit: risk ratio, given the high prevalence of polypharmacy in elderly patients. Furthermore, physiological changes that occur with aging may affect the pharmacokinetics of administered drugs and need to be taken into consideration.

Run training versus cross-training: effect of increased training on circulating leukocyte subsets.

The purpose of this study was to determine the effects of increased training via cross-training (run + cycle) and run training on circulating leukocyte subsets. Male runners (N = 11) participated in two randomly assigned increased training (IT) periods after 30 d of normal training (NT). Each IT began after a 14 d period of reduced training (80% of NT) followed by 10 d of IT (200% of NT). During IT, the subjects ran in the afternoon for 10 d (100% NT) and performed 8 additional training sessions in the morning (100% NT) on a treadmill (ITRT) or a bicycle ergometer (ITCT). Blood samples were obtained before (D0), on day 5(D5) and after 10 d (D11) of ITRT and ITCT. A significant increase in the CD4+/CD8+ ratio occurred at D5 compared with D0 and D11. The CD4+/CD8+ ratio was significantly lower during ITRT compared with ITCT at D11. The number of circulating CD3+, CD4+, and CD8+ cells were significantly reduced at D11 compared with D0. In conclusion, 10 d of IT resulted in a significant reduction in the number of circulating T cells independent of the training mode and a reduction in the CD4+/CD8+ ratio for ITRT but not for ITCT.