Central and Peripheral Contributions to Fatigue: Neurophysiological Correlates of Endurance Exercise

Abstract

Background: Fatigue during prolonged endurance exercise arises from both muscular and central nervous system factors. The brain and spinal cord contribute to performance decline, the interaction between central and peripheral mechanisms is not fully understood. Objective: To investigate the indication of central and peripheral fatigue during endurance exercise. It aims to identify the neurophysiological changes that contribute to performance decline and increased perception of effort. Methodology: In this study, 80 trained adult athletes of the Punjab Sports Board were recruited, and all were physically healthy, without any neuromuscular disease, and aged between 18 and 35. Participants were instructed to refrain from hard exercise, caffeine, and alcohol for 24 hours before testing and to take a light meal at least two hours before exercise. Trained athletes did an endurance cycling test till they were exhausted. Transcranial magnetic stimulation was used to see central fatigue, and electromyography checked muscle activity, conduction speed, and amplitude for the peripheral side. Near-infrared spectroscopy looked at muscle oxygen levels. Participants also gave their exertion rating. Testing to determine fatigue markers was done using a cycle ergometer. Paired-sample t-tests were made to compare pre- and post-intervention values. Pearson correlation coefficients were calculated to examine associations between central markers. Results: After cycling, motor-evoked potentials dropped from 5.8±0.6 mV to 4.2±0.5 mV, so central fatigue was clear. Electromyography conduction speed fell (4.5±0.3 to 3.8±0.4 m/s) and amplitude too (2.1±0.2 to 1.6±0.2 mV), meaning muscles were tiring. Near-infrared spectroscopy showed oxygenation going down from 72±5% to 58±6%. Perceived effort increased from 12±2 to 18±1. Correlation showed a moderate link (r=0.46, p<0.05) between central and peripheral changes, so both sides were involved together. Conclusion: Endurance fatigue in trained adults arises from central and peripheral mechanisms that occur simultaneously. This results in the brain reducing its push muscles after prolonged physical activity such as endurance cycling. Understanding this can help athletes and normal people plan training better, avoid overdoing it, and maybe perform smarter.