Objective This cross-sectional observational study examined muscle oxygen saturation (SmO2) and additional Near-Infrared Spectroscopy (NIRS)-derived parameters—oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), hemoglobin difference (Hb Diff), and total hemoglobin levels (tHb)—in the vastus lateralis (VL) and biceps femoris (BF) muscles between athletes and sedentary individuals during isokinetic maximal concentric (CON) and eccentric (ECC) contractions executed at 60, 180, and 300°/s speeds. Methods Thirty-one male participants (17 elite volleyball athletes, 14 sedentary) underwent a testing protocol using an isokinetic dynamometer. NIRS sensors recorded SmO2, O2Hb, HHb, Hb Diff, and tHb on the VL and BF during maximal CON and ECC sets at each speed. Two-way repeated-measures ANOVA (speed × group × contraction) was applied; normality was verified (Shapiro-Wilk), and Greenhouse-Geisser corrections were used if needed. Data are reported as mean ± SD. Results In the VL, high speed (300°/s) significantly raised SmO2 and tHb relative to 60°/s (p < 0.05). In BF, SmO2 was stable across speeds, although Hb Diff increased at 300°/s (p = 0.008). At 60°/s, VL CON produced greater tHb, O2Hb, and Hb Diff than ECC (p < 0.001); in BF at 60°/s, ECC produced higher O2Hb and Hb Diff than CON (p < 0.001). Athletes had higher VL tHb and O2Hb than sedentary individuals (p < 0.05); BF group differences were minimal. Conclusions Isokinetic velocity and contraction mode significantly altered muscle oxygenation in a muscle-specific manner. High-speed isokinetic CON exercises may enhance oxygenation and local blood flow in the VL of the quadriceps, potentially supporting muscle function, while the hamstrings` limited responsiveness to speed variations highlights the need for alternative strategies. CON vs. ECC actions also elicited distinct oxygenation in each muscle, reflecting differences in contraction-specific physiological demands. These findings - based on measured NIRS variables - highlight how velocity, contraction type, and training status modulate muscle oxygen dynamics, providing a physiological basis for tailoring training and rehabilitation protocols.
© Copyright 2026 BMC Sports Science, Medicine and Rehabilitation. BioMed Central. Alle Rechte vorbehalten.