Search Results

This study examined gastric emptying, core temperature, and sprint performance during prolonged intermittent shuttle running in 30 °C when ingesting a carbohydrate-electrolyte solution (CES) or favored water (FW). Nine male soccer players performed 60 min of shuttle running, ingesting fluid before exercise and every 15 min during exercise. Gastric emptying was measured using a double-sampling aspiration technique, and intestinal temperature was monitored via ingested capsules. There were no differences between trials in the total fluid volume emptied from the stomach during each exercise period (P = 0.054). The volume emptied every 15 min was 244 ± 67 mL in the CES trial and 273 ± 66 mL in the FW trial. Intestinal temperature was higher during exercise in the CES trial (P = 0.004), and cumulative sprint time was shorter (P = 0.037). Sprint performance was enhanced by the ingestion of a CES, which resulted in elevated core temperatures, and the rate of gastric emptying remained similar between solutions.

Previous research findings indicate that environmental temperature can influence exercise-induced oxidative-stress responses, although the response to variable temperatures is unknown. The purpose of this study was to investigate the effect of warm, cold, and “neutral,” or room, environmental temperatures on the blood oxidative stress associated with exercise and recovery. Participants (N = 12, age 27 ± 5 yr, VO_2max = 56.7 ± 5.8 ml · kg^-1 · min^-1, maximal cycle power output = 300 ± 39 W) completed 3 exercise sessions consisting of a 1-hr ride at 60% W_max, at 40% relative humidity in warm (33 °C), cold (7 °C), and room-temperature environments (20 °C) in a randomized crossover fashion. Rectal core temperature was monitored continually as participants remained in the respective trial temperature throughout a 3-hr recovery. Blood was collected preexercise and immediately, 1 hr, and 3 hr postexercise and analyzed for oxidative-stress markers including ferric-reducing ability of plasma (FRAP), Trolox-equivalent antioxidant capacity (TEAC), lipid hydroperoxides, and protein carbonyls. Core temperature was significantly elevated by all exercise trials, but recovery core temperatures reflected the given environment. FRAP (p < .001), TEAC (p < .001), and lipid hydroperoxides (p < .001) were elevated after warm exercise while protein carbonyls were not altered (p > .05). These findings indicate that moderate-intensity exercise and associated recovery in a warm environment elicits a blood oxidative-stress response not observed at comparable exercise performed at lower temperatures.

Wireless microtechnologies are rapidly emerging as useful tools for sport scientists to move their work out of the laboratory and into the field. The purpose of this report is to describe some of the practical aspects of using ingestible radiotelemetric temperature sensors in sport physiology. Information is also presented to demonstrate the utility of this technology in understanding individual differences in coping with environmental stress, optimizing heat adaptation, and fine-tuning competition strategy (pacing). Wireless core-temperature technology has already revolutionized field monitoring of elite athletes training and competing in extreme environments. These technologies are valuable tools for sport scientists to better understand the interaction between the physiology of exercise and the environment.

This case study was conducted as an attempt to quantify racecar-driver core body temperature and heart rate (HR) in real time on a minute-by-minute basis and to expand the volume of work in the area of driver science. Three drivers were observed during a 15-lap, 25-min maximal event. Each driver competed in the closed-wheel, closed-cockpit sports-car category. Data on core body temperature and HR were collected continuously using the HQ Inc. ingestible core probe system and HR monitoring. Driver 1 pre- and postrace core temperatures were 37.80°C and 38.79°C, respectively. Driver 2 pre- and postrace core temperatures were 37.41°C and 37.99°C. Driver 1 pre- and postrace HRs were 102 and 161 beats/min. Driver 2 pre- and postrace HRs were 94.3 and 142 beats/min. Driver 1’s physiological strain index (PSI) at the start was 3.51. Driver 2’s PSI at the start was 3.10. Driver 1 finished with a PSI of 7.04 and driver 2 with a PSI of 3.67. Results show that drivers are continuously challenged minute by minute. In addition, before getting into their cars, the drivers already experience physiological and thermal challenges. The data suggest that drivers are getting hot quickly. In longer events, this represents the potential for severe heat injury. Investigating whether the HRs observed are indicative of work or evidence of a thermoregulatory-associated challenge is a direction for future work. The findings support the value of real-time data collection and offer strong evidence for the expansion of research on driver-athletes.

The purpose of this study was to examine the effect of environmental temperature on variability in power output, self-selected pacing strategies, and performance during a prolonged cycling time trial. Nine trained male cyclists randomly completed four 40 km cycling time trials in an environmental chamber at 17°C, 22°C, 27°C, and 32°C (40% RH). During the time trials, heart rate, core body temperature, and power output were recorded. The variability in power output was assessed with the use of exposure variation analysis. Mean 40 km power output was significantly lower during 32°C (309 ± 35 W) compared with 17°C (329 ± 31 W), 22°C (324 ± 34 W), and 27°C (322 ± 32 W). In addition, greater variability in power production was observed at 32°C compared with 17°C, as evidenced by a lower (P = .03) standard deviation of the exposure variation matrix (2.9 ± 0.5 vs 3.5 ± 0.4 units, respectively). Core temperature was greater (P < .05) at 32°C compared with 17°C and 22°C from 30 to 40 km, and the rate of rise in core temperature throughout the 40 km time trial was greater (P < .05) at 32°C (0.06 ± 0.04°C·km^–1) compared with 17°C (0.05 ± 0.05°C·km^–1). This study showed that time-trial performance is reduced under hot environmental conditions, and is associated with a shift in the composition of power output. These finding provide insight into the control of pacing strategies during exercise in the heat.