Spanoudaki S, Maridaki M, Karatzanos E, Bogdanis GC, Spanoudaki C and Baltopoulos P
Background: Cardiorespiratory and hormonal responses were investigated during and after prolonged exercise of constant and alternating exercise intensity. Methods: Ten healthy males underwent two main cycling exercise trials at the same overall power output, lasting one hour each. During the first trial, exercise intensity was constant at 70±5% VO2max, while during the second trial, exercise intensity was alternated between 47±2% VO2max for 40 s and 120% VO2max for 20 s. Results: Oxygen uptake (VO2) and heart rate (HR) were higher in constant compared with alternating intensity exercise (VO2: 32.5±6.6 vs. 29.8±5.9 ml/kg/min, p<0.05; HR: 152 ± 16 vs. 142 ± 15 b/min, p<0.05). Pulmonary ventilation, respiratory exchange ratio and blood lactate were similar in both trials. Plasma adrenaline and growth hormone during and 1 hour after exercise were similar in both trials, while nor-adrenaline was higher during constant intensity exercise (p<0.05). Significant time effects were found for all cardiorespiratory, lactate and hormonal parameters. Conclusions: Constant and alternating intensity exercise of the same mean intensity and duration provoked similar changes in terms of stress and blood- lactate, while VO2 and HR responses and nor-adrenaline concentration were higher when exercise intensity was constant, suggesting that constant exercise impose greater demand on the cardiovascular system.
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