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

Abstract

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<0.001). The IND responses were consistent with the COMP response as all subjects demonstrated a negative, cubic relationship (R=0.88-0.99). There was no difference (p=0.343) in resting SmO2 values between Day 1 (60.0±13.9%) and Day 2 (56.0±11.7%). The resting SmO2 values demonstrated "poor" to "fair" reliability (ICC: 0.300, 95% CI: -0.265-0.716; SEM: 10.6%; CoV: 18.2%; MD: 29.4%). CONCLUSION: The negative, cubic SmO2 response may suggest a compromise in local blood flow due to increased intramuscular pressure during LE reps performed to failure at 50% 1RM. The "poor" to "fair" reliability may be due to high adipose tissue thickness (ATT) (9.3±4.1 mm), concentration of melanin in the skin, or external pressure applied on the device which can influence the SmO2 response. Although the IND responses were consistent with the COMP responses, recruiting subjects with lower ATT values may provide more reliable test-retest resting SmO2 values. ABSTRACT FROM AUTHOR