Abstract
During high-intensity exercise, oxygen uptake increases until maximal oxygen consumption (VO2max) is reached. The rate at which the body uptakes oxygen can be described throughVO2 kinetics. When high-intensity exercise is preceded by an additional bout of high-intensity exercise, VO2 kinetics are altered so that VO2max is achieved sooner. Therefore, it is possible that VO2 kinetics are further altered by subsequent bouts of high-intensity exercise. To investigate the time to reach VO2max during subsequent intervals at pVO2max lasting 60% Tmax in well-trained cyclists. Twelve male cyclists completed a graded exercise test (GXT) to determine their pVO2max, followed by a time to fatigue test later that same day to determine their Tmax. After 7 days, subjects returned and completed 5 intervals at pVO2max for a duration of 60% Tmax. In between intervals, subjects pedaled at a low load (20W) for a duration equal to their interval duration. Expired air and heart rate (HR) was recorded as 20-second averages. Analysis of peak values (VO2, HR, and VE) between the GXT and interval trials was completed with a paired t-test. Analysis of interval variables (time to reach VO2max, peak VO2 HR, VE, and RER was completed with a one-way repeated measures ANOVA. A p-level of <0.05 was used for significance. When significance was found a Tukey post hoc test was used for comparisons. There was a significant increase in peak values of VO2 and VE in the interval trials compared to the GXT (70.5 ml/kg/min-1 from 67.8, and 183.2 L/min from 168.7 respectively). There was a significant decrease in time to reach VO2max (63.37% to 32.97%) over the duration of the intervals, with intervals 1 and 2 showing significant differences from interval 5. Peak VO2 showed a significant increase (63.2 ml/kg/min-1 to 71.23) over the duration of the intervals, with intervals 1 and 2 showing significant differences from interval 5. Both VE (144.6 L/min to 181.1) and HR (171.4 bpm to 183.8) showed significant increases over the duration of the interval, with significant changes seen in intervals 1, 2 and 3 compared to interval 5. Only the peak RER (1.45) in the interval 1 was significantly different from the last interval (1.25). In addition, only the peak RER achieved during the interval 1 was significantly higher than the peak RER from the GXT (1.15). The findings from this study support the theory that VO2 kinetics in a heavy exercise bout are altered to allow VO2max to be reached sooner when that exercise is preceded by another heavy exercise bout. In addition, our data supports the idea that VO2 kinetics will continue to be altered in a further subsequent bout, but will reach a point where additional bouts have no affect on the time to reach VO2max.