Jämförelse mellan HIIT och kontinuerligt träning på syreupptagning och prestation

[King Grub]

The early time course of adaptation of pulmonary O2 uptake (VO2p) (reflecting muscle O2 consumption) and muscle deoxygenation kinetics (reflecting the rate of O2 extraction) were examined during highintensity interval (HIT) and lower-intensity continuou (END)training. Twelve male volunteers underwent 8 sessions of either HIT (8-12 x 1 min intervals at 120% VO2max separated by 1 min rest) or END (90-120 min at 65% VO2max). Subjects completed step-transitions to a moderate-intensity work rate ( approximately 90% estimated lactate threshold) on 5 occasions throughout training, and ramp incremental and constant-load performance tests at pre-, mid- and post-training. VO2p was measured breath-by-breath by mass spectrometry and volume turbine. Deoxygenation (Delta[HHb]) of the vastus lateralis muscle was monitored by near-infrared spectroscopy. The fundamental phase II time constant for VO2p (tau VO2) and deoxygenation kinetics (effective time constant, tau' = (TD + tau) Delta[HHb]) during moderate-intensity exercise were estimated using nonlinear least-squares regression techniques. The tauVO2 was reduced by ~20% (p < 0.05) after only 2 training sessions and by ~40% (p < 0.05) after 8 training sessions (i.e., post-training), with no differences between HIT and END. The tau'Delta[HHb] (~20 s) did not change over the course of 8 training sessions. These data suggest that faster activation of muscle O2 utilization is an early adaptive response to both HIT and lower-intensity END training. That Delta[HHb] kinetics (a measure of fractional O2 extraction) did not change despite faster VO2p kinetics suggests that faster kinetics of muscle O2 utilization were accompanied by adaptations in local muscle (microvascular) blood flow and O2 delivery, resulting in a similar "matching" of blood flow to O2 utilization. Thus faster kinetics of VO2p during the transition to moderate-intensity exercise occurs after only 2 days HIT and END training, and without changes to muscle deoxygenation kinetics, suggesting concurrent adaptations to microvascular perfusion.

J Appl Physiol. 2009 May 14. Effect of Short-Term High-Intensity Interval Training versus Continuous Training on O2 Uptake Kinetics, Muscle Deoxygenation and Exercise Performance.