Exploration of the associations between muscle oxygen saturation and skin temperature responses during isokinetic strength exercise.

Previous studies suggested that skin blood flow, and therefore skin temperature affect changes in muscle oxygenation (SmO2). Given that near-infrared spectroscopy (NIRS) measurements consider a depth of a few centimeters to capture changes in SmO2, in this study, we aimed to explore whether a relationship between skin temperature and SmO2 is observed after sets of isokinetic strength exercises. Seventeen males (age: 25 ± 6 years old and body mass: 74.7 ± 12.4 kg) completed five series of 30 maximum unilateral (preferred) knee extension isokinetic exercises at 180º·sec-1 with a 60-second rest between series to exercise quadriceps muscles. At baseline, after a warm-up, and 50 seconds after each series of exercise, SmO2 related to vastus lateralis and skin temperature of the anterior thigh were evaluated in the exercised and non-exercised legs. Significance was established at p < 0.05. Exercise reduced mean skin temperature throughout the consecutive repetitions in both the exercised and non-exercised legs (p < 0.01). SmO2 increased during exercise only in the exercised leg. No significant correlations were found between skin temperature and SmO2, and weak correlations were observed between skin temperature and total haemoglobin for absolute (r = 0.4 and p < 0.001) and delta values (r = 0.3 and p = 0.03) only in the non-exercised leg. In conclusion, this exploratory study suggests that skin temperature and SmO2 are compatible as they explain different physiological responses, although these measurements are not associated during a controlled exercise.