Abstract
Yet undefined neural mechanisms modulate fatigue perception during intense exercise. The prefrontal cortex (PFC), which may influence volitional control of exercise termination, displays relatively constant deoxygenated hemoglobin (HbR) levels during lighter exercise, and switches to rapidly increasing HbR preceding exhaustion. This switch-point (HbR threshold) may reflect volitional control during exercise, and may therefore occur, paralleling individual fitness, at higher workloads in more fit individuals. PURPOSE: To investigate non-invasively, using Diffuse Optical Spectroscopy (DOS) in healthy children, PFC HbR thresholds before and after a 10-week supervised exercise intervention METHODS: Fourteen children (8M, age 14±2 yrs) underwent a 10-week exercise training program (60min of moderate to intense exercise 3 times/week); incremental cycle exercise testing to exhaustion was performed before and after training, during which PFC HbR was measured via a DOS probe on the left forehead, connected to a continuous-wave near-infrared spectroscopy system (TRS200 Hamamatsu, Japan). HbR thresholds were calculated via linear segmented regression. RESULTS: Eight children significantly increased maximal work-rates after training (+22±2 watts, p<0.0001); their HbR threshold increased by 19±9 watts (132±13 vs 113, p<0.05). Conversely, 6 children displayed unchanged maximal work-rates, and their HbR was proportionally unaffected (−8±1% vs pre-training, NS). CONCLUSION: The PFC HbR threshold during incremental exercise can be displaced toward greater absolute workloads with improved fitness, supporting its potential role in volitional control of early exercise termination. NIH NICHD P01HD048721 & UL1 TR000153
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