The intermittent exercise profile in tennis consists of short, partially intense exercise bouts, followed by longer resting periods. The nature of this type of workload may lead to different physiological responses from continuous exercises such as running or cycling. From a health-related perspective and from a performance-oriented point of view, it is beneficial to know the specific responses regarding substrate changes and utilisation during such exercise. Researchers at the German Sport University examined specific physiological characteristics in 12 nationally ranked senior tennis players (6 female and 6 male) during a two-hour singles tennis match, and compared these to a constant treadmill run with similar oxygen uptake. Mean oxygen uptake during tennis (23.1 ± 3.1 ml·kg-1·min-1 in women and 25.6 ± 2.8 ml·kg-l·min-l in men) was measured by a portable spirometry-telemetry-system and corresponded to 56 % (women) or 54% (men) of their respective VO2 max. The oxygen uptake data were used to set the workload during a two-hour treadmill run at a constant level. Heart rate (140.1±15.5 vs. 126.4±15.1 bpm), capillary lactate (1.53±0.65 vs. 1.01±0.38 mmol.L-1) and capillary glucose (98.2±15.1 vs. 78.2±10.1 mg·dl-1), as well as the respiratory exchange ratio (0.93±0.03 vs. 0.88±0.03), were higher (p <0.01) in tennis compared to running, at the measured time points. After 30 minutes of tennis, serum concentrations of tree fatty acids and glycerol were significantly increased, whereas evidence of increased lipolysis appeared comparatively later in running. Post-exercise urine concentrations of epinephrine and norepinephrine were higher (p<0.01) in tennis. The results point to an overall stronger glycogenolytic, glycolytic and lipolytic activity in tennis than in continuous running exercise at a similar mean oxygen uptake, Dr. Ferrauti said. The effects can mainly be attributed to a significantly higher sympathetic activity. Consequently, the carbohydrates seem to be predominantly responsible for energy metabolism (70-80%) as estimated from respiratory exchange ratio, he concluded.
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