The use of near-infrared spectroscopy (NIRS) to measure muscle oxygenation (SmO2) is gaining popularity as a training metric, however interpreting the values may be difficult. SmO2 is the percentage of hemoglobin in the capillaries of skeletal muscle that is oxygenated, measured on either an absolute or relative scale. SmO2 can be used to interpret the level of effort exerted by that particular muscle. PURPOSE: To determine if muscle oxygenation from wireless NIRS devices will vary with their anatomical placement on cross country skiers during a sport-specific graded exercise test (GXT). METHODS: 10 well-trained competitive collegiate Nordic skiers (7 women, 3 men; Mean±SD: 22±2 yrs; 58.4±7.7 ml/kg/min VO2MAX; 23.2±1.5 kg/m2 BMI) each performed a roller skiing GXT to determine lactate threshold (LT) and VO2MAX. Each skier wore three wireless NIRS devices on the left side of the body on the belly of the triceps, the vastus lateralis, and the lateral head of the gastrocnemius. The devices were synchronized together on the same time series and raw data was collected at 1 Hz, but the data were summarized afterwards over the last 10 secs at three common time points: Stage just before LT (S1); stage just after LT (S2); at VO2MAX (S3). The resulting SmO2 values were analyzed using 2-factor RM ANOVA to compare SmO2 at the three time points for each muscle (alpha = 0.05). RESULTS: SmO2 decreased significantly (P<0.001) between each successive time point (i.e., S1 to S3) for the gastrocnemius (58.27±0.23%, 48.96±0.16%, 23.70±0.06%, respectively) and the vastus lateralis (54.19±0.18%, 42.64±0.11%, 19.83±0.04%, respectively), but not for the triceps (49.80±0.11%, 46.29±0.09%, 40.09±0.06%; P=0.063, respectively). CONCLUSION: While changes in SmO2 were consistent across skiers for the gastrocnemius and vastus lateralis, they were inconsistent for the triceps. Thus, SmO2 measures were dependent upon anatomical location and test stage during a skiing-specific GXT. The variability in SmO2 measurements between athletes taken at the triceps suggest that other extraneous factors may influence upper-body utilization in Nordic Skiers during maximal and submaximal efforts. This type of data may be useful for coaches or athletes to assess points of weaknesses, grade specific technique changes, and/or under-utilization of muscle groups.

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