Key result
Constant torque isometric exercise induces greater performance fatigability than RPE-clamp while both enhance microvascular reactivity.
Why the study?
To compare NIRS-derived microvascular function, muscle oxygenation dynamics, and fatigability during sustained isometric forearm flexion between an RPE-Clamp condition and a matched constant torque condition.
Does sustained isometric forearm flexion at RPE-Clamp compared to constant torque affect microvascular function and fatigability in healthy males?
Does sustained isometric forearm flexion at RPE-Clamp compared to constant torque affect microvascular function and fatigability in healthy males?
p-value: p=<0.001
Both RPE-clamped and constant torque isometric exercise modalities enhance microvascular reactivity, though constant torque induces greater fatigability and desaturation.
RPE-clamp isometric exercise may reduce fatigability versus constant torque; hypothesis-generating for microvascular reactivity in healthy adults.
Objective This study compared near‐infrared spectroscopy (NIRS)‐derived microvascular function, muscle oxygenation (SmO 2 ) dynamics, and fatigability during sustained isometric forearm flexion under two conditions: a rating of perceived exertion (RPE) level of 3 (RPE‐Clamp) versus a constant torque (CT) matched to the torque produced during the first second of RPE‐Clamp. Methods Thirteen healthy males (22.2 ± 4.7 year) completed both tasks on separate days. SmO 2 was measured during exercise, maximal voluntary isometric contractions (MVIC) were performed before and after exercise, and time to task failure (TTF) was recorded. Vascular occlusion tests (VOT) were used to assess microvascular function pre‐ and post‐exercise. Results CT induced significantly greater performance fatigability than RPE‐Clamp ( p < 0.001), despite similar TTF ( p = 0.171). SmO 2 significantly decreased during early ( p = 0.001) and final ( p = 0.028) phases of CT, while increasing during mid ( p < 0.001) phases in RPE‐Clamp. Post‐VOT indicated a significantly reduced desaturation rate (slope 1; p < 0.001), a greater extent of tissue hypoxia (minimum SmO 2 ; p = 0.003), and increased microvascular reactivity (slope 2; p = 0.021) than pre‐VOT, with greater peak re‐saturation (MaxSmO 2 ; p = 0.010) observed in CT than RPE‐Clamp. Conclusions Despite greater fatigability and desaturation in CT, both exercise modalities may enhance microvascular reactivity. Prolonged isometric exercise and subsequent hypoxic stress may contribute to a reduced desaturation rate post‐exercise.
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Kwak et al. (2025) studied Healthy (n=13). Sustained isometric forearm flexion at a rating of perceived exertion (RPE) level of 3 (RPE-Clamp) vs. Constant torque (CT) matched to the torque produced during the first second of RPE-Clamp was evaluated on Performance fatigability (p=<0.001). Constant torque isometric exercise induced significantly greater performance fatigability than RPE-Clamp (p<0.001), though both modalities may enhance microvascular reactivity.
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