Cardiovascular and thermal responses of triathlon performance

KREIDER, R. B., T. BOONE, W. R. THOMPSON, S. BURKES, and C. W. CORTES. Cardiovascular and thermal responses of triathlon performance. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 385- 390, 1988. Triathletes typically train each triathlon event separately. Therefore, to determine the cardiovascular and thermal differences between training and triathlon performance, nine male triathletes performed a simulated 75-min (40 km) control bike and a 40-min (10 km) control run at 70% of maximal oxygen uptake. Control data were compared to data derived from a simulated triathlon (0.8-km swim, 75-min bike, and 40-min run). Results demonstrated that prior swimming significantly decreased (P <0.05) triathlon cycling work output (191 ± 4.2 to 159 ± 7.6 W) producing mean differences (P<0.05) in oxygen uptake (3.18 ± 0.1 to 3.01 ± 0.1 l·min−1), ventilation (84.7 ± 4 to 80.4 ± 4.2 l·min−1). stroke volume (128 ± 7.1 to 118 ± 3.5 ml·min−1), cardiac output (20.7 ± 1.2 to 18.9 ± 0.8 l·min−1), mean arterial pressure (105 ± 3.8 to 96 ± 7.9 mm Hg) and rectal temperature (38.2 ± 0.2 to 38.4 ± 0.3°C). Triathlon running, while performing identical control work output, elicited significant increases (P<0.05) in oxygen uptake (3.41 ± 0.1 to 3.85 ±0.1 l·min−1), ventilation (91.3 ± 3.3 to 104.2 ± 2.8 l·min−1), heart rate (161 ±3.1 to 174 ± 3.6 beats·min−1),arteriovenous oxygen difference (15.3 ± 0.2 to 17.2 ± 0.3 ml-100 ml−1) and rectal temperature (38.3 ± 0.2 and 39.2 ± 0.3°C) with significantly lower (P<0.05) stroke volume (138 ± 2.4 to 129 ± 3.6 ml·min−1) and mean arterial pressure (102 ± 11.2 to 89 ± 5.5 mm Hg). Results demonstrate that triathlon performance elicited cardiovascular and thermal adjustments not experienced when performing the events independently. Findings appear to be a result of thermoregulatory and cardiovascular adaptations combined with a decrease in mechanical efficiency observed during prolonged triathlon performance.