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Gordon G. Sleivert

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.

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Thomas Zochowski, Elizabeth Johnson, and Gordon G. Sleivert


Warm-up before athletic competition might enhance performance by affecting various physiological parameters. There are few quantitative data available on physiological responses to the warm-up, and the data that have been reported are inconclusive. Similarly, it has been suggested that varying the recovery period after a standardized warm-up might affect subsequent performance.


To determine the effects of varying post-warm-up recovery time on a subsequent 200-m swimming time trial.


Ten national-caliber swimmers (5 male, 5 female) each swam a 1500-m warm-up and performed a 200-m time trial of their specialty stroke after either 10 or 45 min of passive recovery. Subjects completed 1 time trial in each condition separated by 1 wk in a counterbalanced order. Blood lactate and heart rate were measured immediately after warm-up and 3 min before, immediately after, and 3 min after the time trial. Rating of perceived exertion was measured immediately after the warm-up and time trial.


Time-trial performance was significantly improved after 10 min as opposed to 45 min recovery (136.80 ± 20.38 s vs 138.69 ± 20.32 s, P < .05). There were no significant differences between conditions for heart rate and blood lactate after the warm-up. Pre-time-trial heart rate, however, was higher in the 10-min than in the 45-min rest condition (109 ± 14 beats/min vs 94 ± 21 beats/min, P < .05).


A post-warm-up recovery time of 10 min rather than 45 min is more beneficial to 200-m swimming time-trial performance.

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Michael D. Nelson, Lynneth A. Stuart-Hill, and Gordon G. Sleivert


To evaluate the influence of acute hypervolemia, achieved through the ingestion of a sodium citrate-rich beverage, on cardiovascular strain and thermoregulatory function, during moderate-intensity aerobic exercise in a warm environment. Sodium citrate’s ability to increase buffering capacity was also assessed.


Twelve endurance-trained athletes completed two blind randomized treatment trials, separated by a minimum of seven days, on a cycle ergometer under heat stress (30.9°C, 64% RH). The subjects ingested 12 mL·kg−1of (1) Gatorade, the control (CNT), or (2) sodium-citrate plus Gatorade (NaCIT: 170 mmol Na+L−1) before cycling at 15% below ventilatory threshold (VT) for 62 minutes. Core and skin temperature, expired gas samples, heart rate, and perceived exertion were measured throughout exercise. Blood samples were taken before drinking each beverage, before commencing exercise, and throughout the exercise bout.


Plasma volume (PV) was significantly expanded in the NaCIT trial (3.6 ± 5.5%) and remained significantly higher throughout exercise in the NaCIT trial compared with the CNT trial (P ≤ .05). No significant differences were found in heart rate, in core and skin temperature, or in the metabolic data between the treatment groups. NaCIT significantly increased [HCO3 ], base excess, and pH throughout the trial.


Acute oral ingestion of high-sodium citrate beverages before moderate exercise induces mild levels of hypervolemia and improves blood-buffering capacity in humans; however, mild hypervolemia during 62 minutes of moderate exercise does not reduce physiological strain or improve thermoregulation.