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Abstract

Fatigue limits performance during resistance training by directly impairing muscle function and brain activity. Does muscle fatigue correspond to changes in brain activity? PURPOSE: The purpose of the study is to determine the relatipnship between brain and muscle oxygenation during exercise-induced muscle fatigue between sedentary and athletes. METHODS: Eight participants, four sedentary and four athletes, were included. The protocol was four sets of twelve repetitions of the bench press, with the weight adjusted to induce failure on the final set. Oxygenation levels in the left prefrontal cortex and the right triceps muscle were continuously monitored using near-infrared spectroscopy (NIRS) (Oxymon). Blood pressure was continuously measured with a finger cuff (Finapres). Baseline was recorded for five minutes with participants in a supine position. RESULTS: At the point of muscle failure during the fourth exercise set, trained participants exhibited higher muscle oxygenation (MuO2HB) and deoxygenation (MuHHB) compared to untrained participants (3.767 vs. 2.182; 9.848 vs. 4.017, respectively). No difference was observed in total muscle haemoglobin (MutHB) (6.200 vs. 6.081). During the recovery period, MuO2HB and MutHB were elevated in trained participants (4.535 vs. 0.55; 6.587 vs. 2.610, respectively), with no difference in MuHHB (2.054 vs. 2.052). When comparing the first set to the last, a 15.68-fold increase in MuO2HB was observed in trained participants, compared to a 0.31-fold increase in untrained participants.At the cerebral level, during exercise to failure, trained individuals showed a 10-fold increase in cerebral oxygenation (CerO2HB) (16.503 vs. 1.6341) and more than a 20-fold increase in cerebral total haemoglobin (CertHB). There was no difference in cerebral deoxygenation (CerHHB) (2.800 vs. 2.182). Notably, trained individuals sustained higher CerO2HB and CertHB compared to untrained individuals when compared the last set to the first. CONCLUSION: Our preliminary data indicate that trained individuals demonstrate a distinct relationship between muscle and brain activity during exercise-induced fatigue. Notably, they maintained higher CerO2HB during the final set, which may contribute to sustained muscle performance.

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