MUSCLE OXYGEN SATURATION MEASUREMENTS TRACK CHANGES DUE TO TRAINING IN IRONMAN TRIATHLETES

Abstract

Athletes are continuously looking at ways to improve their training techniques and thus maximize performance. Lactate threshold has been used as a common exercise intensity for endurance athletes during training. Previously we have shown that muscle oxygen saturation (StO2) can be used to determine blood lactate breakpoint and maximal lactate steady state speed. PURPOSE To determine if muscle StO2 tracks decrements and increments in training throughout an entire season. METHODS Sixteen triathletes (males = 12, females = 4) training for an Ironman event were monitored four times (Jan, March, May and Aug) prior to a Sept Ironman competition. Five, 6-minute stage incremental and then maximal running tests were performed during each time period, with oxygen uptake variables, blood lactate and muscle oxygen saturation of the gastrocnemius through near-infrared spectroscopy (NIRS) determined. Thirteen athletes finished the Ironman (mean time = 11:41:56), two did not compete due to injuries, and one did not finish. RESULTS Mean muscle StO2 was highest in the athletes during the Aug testing, two weeks prior to the Ironman event. Mean muscle StO2 was much lower during March and May when the athletes were in their preparation phase of training which was marked by a very high training volume. For example, mean muscle StO2 for the third workload was: Jan = 56%, March = 48%, May = 53% and Aug = 72%. Mean blood lactate curves responded similarly to the muscle StO2 curves, but had less differentiation between the different testing points (mean third workload: Jan = 3.0 mM, March = 2.5 mM, May = 2.4 mM, Aug = 2.6 mM). Most athletes complained of being fatigued in March and May, but ready for the Ironman event in Aug, parallel to what the muscle StO2 and blood lactate results seemed to indicate. CONCLUSIONS Muscle StO2 appears to track changes in blood lactate and training over an eight-month training period and therefore should be a useful tool in monitoring athletes during training. Supported by Hutchinson Technology, Inc., Hutchinson, MN