Integrating mechanical, physiological, and muscle oxygenation responses during field-based tethered repeated-sprint exercise in male professional soccer players.

Repeated-sprint ability is a key determinant of soccer performance. However, some mechanical and physiological responses underlying this task remain incompletely understood. This study characterized mechanical responses (force, velocity, and power) and regional muscle oxygen saturation (rSmO2) in the vastus lateralis (VL) and biceps brachii (BB) during field-based tethered repeated-sprint exercise (RSE). Associations between muscle oxygenation and mechanical performance, as well as post-exercise rSmO2, heart rate (HR), and blood lactate (LAC), were also examined. Ten professional soccer players performed a tethered Running Anaerobic Sprint Test (6 × 35-m all-out sprints separated by 10-s intervals), while mechanical variables and rSmO2 were continuously recorded. Muscle oxygenation differed according to muscle function throughout exercise and recovery. The VL exhibited greater deoxygenation during sprints, whereas the BB showed a more preserved oxygenation profile. Associations between rSmO2 and mechanical performance were observed only during the fifth and sixth sprints. Furthermore, only VL integrated rSmO2 was positively correlated with the velocity fatigue index, whereas BB oxygenation provided complementary information on the physiological adjustments associated with RSE. Post-exercise HR and LAC were not correlated with rSmO2 in both muscles. Simultaneous assessment of locomotor and non-locomotor muscles provides complementary insights into fatigue development and post-exercise recovery RSE.