Muscle Oxygen Saturation to Determine Lactate Thresholds in Spinal Cord Injury Population

This study aimed to compare the intensity when thresholds occur determined with muscle oxygen saturation and blood lactate concentration during a graded exercise test (GXT) in an arm-crank ergometer. Twenty-nine participants were included, divided into non-spinal cord injury (SCI) (N=12) and SCI (N=17) groups. Participants underwent a GXT with 3-minute steps and 1-minute rest intervals. Blood lactate concentration was measured at baseline and after each step, while muscle oxygen saturation was continuously registered in the biceps brachii. Agreement between methods was good at the first threshold [Non-SCI: intraclass correlation coefficient (ICC)=0.46; SCI: ICC=0.51] and excellent at the second threshold (Non-SCI: ICC=0.82; SCI: ICC=0.92). No significant differences were found between groups in bias for the first and second lactate thresholds (p > 0.05). In conclusion, muscle oxygen saturation is valid and reliable for the second lactate threshold determination, with stronger agreement than the first lactate threshold during GXTs using arm-cranking in biceps brachii in Non-SCI and SCI.