Predicting perceived exertion during high-intensity exercise using quantitative MRI: insights from T2* value and muscle cross-sectional area.

This study aimedto investigate the relationship between MRI-derived skeletal muscle biomarkers and subjective exercise intensity, measured by the Rating of Perceived Exertion (RPE). Both T2* value and CSA showed significant time-dependent changes following exercise. The percent change (PC) in T2* immediately after exercise (T2* PC-post/pre) was most strongly associated with RPE (ρ = 0.45,p < 0.01), while CSA showed a weaker correlation. Muscle strength was not significantly associated with RPE.Random forest analysis identified T2* PC-post/pre as the most important predictor of RPE, supported by partial dependence plots showing a nonlinear increase in RPE with higher T2* value changes. T2* value changes after exercise reflect metabolic stress and serve as a more specific predictor of RPE than CSA or muscle strength. These findings highlight the potential of T2* value as a non-invasive biomarker for assessing subjective exercise intensity.