Individual And Composite Muscle Oxygen Saturation Responses Of The Quadriceps To Fatiguing DCER Exercise

PURPOSE: This study examined the individual (IND) and composite (COMP) responses of local muscle tissue oxygen saturation (% SmO2) during submaximal, bilateral leg extension (LE) exercise to failure and the test-retest reliability of resting SmO2 values. METHODS: Thirteen subjects (24±3 years) completed a one-repetition maximum (1RM) for the LE (68±18.5 kg) on Day 1 and repetitions (reps) to failure at 50% 1RM (34±9 kg; 26±5 reps) on Day 2. The SmO2 was measured using continuous wave near-infrared spectroscopy placed on the vastus lateralis of the dominant limb, 66% of the distance between the suprailiac spine and lateral side of the patella. Resting SmO2 was recorded for 1-min prior to completing reps to failure to examine the test-retest reliability of the resting values. The total time to failure for the reps at 50% 1RM was recorded (56±10 sec). Polynomial regression analyses were used to determine IND and COMP SmO2 responses (linear, quadratic, cubic) vs. percent time to failure (5-100%) for reps completed at 50% 1RM. A one-way repeated measures ANOVA (p≤0.05), intra-class correlation coefficient (ICC2,1), standard error of the measurement (SEM), coefficient of variation (CoV), and the minimal difference (MD) was used to determine the test-retest reliability of resting SmO2 (Day 1 vs. Day 2). RESULTS: For the COMP SmO2 response, there was a negative, cubic relationship (R=0.987, p