Does Resistance Exercise Induce Differential Relationships Between Muscle and Brain Oxygenation in Trained Versus Untrained Individuals?

While the benefits of resistance training for muscles are well-documented, its effects on brain activity are less known. PURPOSE: to investigate the changes in oxygenation levels in the brain and muscles during resistance training, comparing these effects between trained and sedentary individuals. METHODS: Eight participants were recruited, four untrained and four athletes. The bench press protocol included one set of twelve repetitions at a weight corresponding to a Rate of Perceived Exertion (RPE) of 6. Oxygenation levels in cortex and the right triceps muscle were continuously monitored using near-infrared spectroscopy (NIRS) (Oxymon). Blood pressure was measured continuously using a finger cuff (Finapres). Baseline was recorded for five minutes with participants in a supine position. RESULTS: Data were normalized relative to baseline rest values. During the bench press exercise, the untrained group exhibited greater increases in muscle oxygenation (4.769 vs 0.918), deoxygenation (2.087 vs 1.231), and total hemoglobin (7.576 vs 0.313) compared to the trained group. Notably, during the 2-minute recovery period, oxygenation in untrained individuals seemed elevated relative to trained individuals (1.792 vs 0.289), while deoxygenation levels were comparable between the two groups (2.298 vs 2.697). In the pre-frontal cortex, untrained individuals showed a more pronounced increase in oxygenation (8.796 vs 7.912) and total hemoglobin (10.114 vs 9.292), with deoxygenation being relatively similar between groups (1.319 vs 1.380). Conversely, during recovery, trained individuals demonstrated elevated levels of oxygenation (1.970-fold increase), deoxygenation (1.154-fold increase), and total hemoglobin (2.010-fold increase). There was no significant difference in blood pressure between groups post-exercise compared to rest. CONCLUSION: Untrained individuals may exhibit greater muscle and brain activation during the bench press exercise, possibly due a more important stress. During recovery, the increased oxygenation and blood flow observed in trained participants may indicate a more efficient recovery process and readiness for subsequent exercise bouts.