Abstract

Heart rate (HR), hematocrit, hemoglobin, blood glucose, and plasma concentrations of lactate, cortisol, and testosterone were monitored in 10 male subjects (Division I, 20.3 +/- 2.5 yrs, VO2max: 58.5 +/- 9.4 ml/kg/min) during singles tennis and a treadmill test. During the on-court session, HR was 144.6 +/- 13.2 beats/min for the 85 min of play. Plasma lactate rose 50 from a post-warmup value of 1.6 +/- 0.6 mmol/l to 2.3 +/- 1.2 mmol/l during play (p>0.05). Blood glucose slightly decreased (8, p>0.05) from a pre-exercise value of 4.6 +/- 0.8 mmol/l as a result of the 10-min warmup. This was followed by a 23 rise (p<0.05) from 4.2 +/-1.0 mmol/l to 5.2 +/- 0.6 mmol/l, measured after the first 30 min of play. Blood glucose subsequently remained steady at slightly above the pre-exercise value. Plasma cortisol rose (9, p>0.05) during the warmup and subsequently decreased (p>0.05) from a post-warmup value of 558.2 +/- 285.2 nmol/l to 337.1 +/- 173.3 nmol/l (a 40 decrease), and remained decreased during recovery. Plasma testosterone rose 22 (p<0.05) from pre-exercise to recovery (13.5 +/- 3.8 nmol/l and 16.6 +/- 2.6 nmol/l, respectively). Although tennis is characterized by periods of high-intensity exercise, the overall metabolic response resembles prolonged moderate-intensity exercise. Verf.-Referat