We measured pre-frontal cortex and muscle oxygenation (HbO2) and deoxygenation (HHb) during a maximal muscular endurance fatigue test to explore the contribution of central and peripheral limitations to short-term maximal exercise performance. We hypothesized that pre-frontal cortex HbO2 would peak prior to termination of the maximal exercise, reflecting “central fatigue”. Healthy physically active males (N=10; mean ± SD age, height, body mass =23.1±3.1 yr; 179.6±3.8 cm; 85.9±7.9 kg) volunteered to perform a maximal knee extension/flexion isokinetic (180degrees/sec) muscular endurance trial of 50-repetitions. Pre-frontal cortex and muscle (right quadriceps femoris) HbO2 and HHb were monitored with a multi-channel NIRS system, expired gases were collected using a ParvoMedics TrueMax 2400 metabolic cart, and heart rate was monitored using a Polar HR monitor. Results (Mean±SD) showed that peak VO2, VE , and HR increased during testing to 2.16±0.24 L/min, 92.3±28.9 L/min, and 164±14 bpm, respectively. Mean quadriceps peak torque and total work was 170.7Nm and 6392.6Nm, respectively. The fatigue index (67±8%) correlated (Pearson R) with peak torque (r=0.74; p<0.05). There was a significant increase (ANOVA) in pre-frontal cortex HbO2 and muscle HHb during the 50-reps, with peak pre-frontal cortex HbO2 (19.6mM) and muscle HHb (13.7mM) occurring at contraction number 38 and 36, respectively. Thereafter, pre-frontal cortex HbO2 gradually decreased to completion of the test (50-reps), while muscle HHb reached a plateau and remained at the same level until the end of the fatigue trial. Both variables correlated with torque output (r=-0.61; -0.53, respectively). These results suggest that 1) NIRS can reliably track changes in pre-frontal cortex HbO2 and muscle HHb during isokinetic muscular endurance fatigue testing; and 2) the peak pre-frontal cortex HbO2 that occurred before termination of the test, simultaneous with a plateau in muscle HHb, would suggest that central factors were implicated in the maximal knee extension muscular exercise fatigue in this study.
University College Dublin (2009) Proc Physiol Soc 15, C36
Oral Communications: Pre-frontal Cortex and Muscle Oxygenation During Maximal Isokinetic Endurance Exercise
J. Neary1, M. Olbert2, M. Kohl-Bareis2, W. Duff1, J. Lazorko1, S. Poloskei1, D. McLeod1, D. G. Candow1
1. Kinesiology & Health Studies, University of Regina, Regina, Saskatchewan, Canada. 2. Biomedical Optics, University of Applied Sciences, Koblenz, Remagen, North Rhine-Westpahlia, Germany.
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