Differences in Oxygenation Kinetics Between the Dominant and Nondominant Flexor Digitorum Profundus in Rock Climbers

Purpose: To examine differences in oxygenation kinetics in the nondominant and dominant flexor digitorum profundus (FDP) of rock climbers. Methods: Participants were 28 sport climbers with a range of on-site abilities (6a+ to 8a French Sport). Using near-infrared spectroscopy, oxygenation kinetics of the FDP was assessed by calculating the time to half recovery (t1/2 recovery) of the tissue-saturation index (TSI) after 3–5 min of ischemia. Results: A 2-way mixed-model ANOVA found a nonsignificant interaction (P = .112) for TSI by sex. However, there was a significant main effect (P = .027) of handedness (dominant vs nondominant FDP). The dominant forearm recovered 13.6% faster (t1/2 recovery mean difference = 1.12 s, 95% CI 0.13–2.10 s) than the nondominant FDP. This was not affected by 6-mo on-site climbing ability or sex (P = .839, P = .683). Conclusions: Significant intraindividual differences in oxygenation kinetics of the FDP were found. Improvements in oxygenation kinetics in the FDP are likely due to the abilities of the muscle to deliver, perfuse, and consume oxygen. These enhancements may be due to structural adaptations in the microvasculature, such as an increase in capillary density and enhanced improvement in capillary filtration.