Acute resistance exercise load modulates brain haemodynamics, working memory, and inhibitory performance

Acute resistance exercise (RE) has been shown to improve executive function (EF), but its effects at different intensities on specific EF domains (e.g., inhibition, working memory) and underlying brain mechanisms (i.e., brain hemodynamics) remain unclear. METHODS: Forty-two young, active, and healthy adults (mean age = 26.9 ± 0.8 years; 24 men) were randomly allocated to one of three experimental groups: 1) RE at high load (HRE) (75% of 1RM), 2) RE at moderate load (MRE) (50% of estimated of 1RM) and 3) a resting control condition (CON). Participants completed Stroop and N-back tasks (i.e., measuring inhibition and working memory) to assess EF at three time points: pre-exercise, post-exercise (Post), and 45 minutes post-exercise (Post45). Functional near-infrared spectroscopy (fNIRS) was used to determine changes in brain hemodynamics during cognitive testing. RESULTS: HRE produced small to moderate improvements in Stroop incongruent trial performance (d=0.40) and moderate gains on the 2-back working memory task (d=0.80 post), with smaller improvements on the 1-back task. In comparison, MRE showed weaker effects on Stroop performance but moderate improvements on the 2-back task (d=0.65). HRE showed increases in right hemisphere oxygenated haemoglobin (O 2 Hb) across tasks, particularly under higher cognitive load (d = 0.65 in congruent Stroop trials). MRE induced smaller but notable O 2 Hb increases (d=0.35–0.54), whereas CON showed little or declining O 2 Hb levels. CONCLUSION: HRE was associated with greater improvements in EF, particularly inhibition and working memory, and was associated with stronger and more sustained functional brain hemodynamics changes compared to MRE. • High-load resistance exercise (HRE) led to greater improvements in inhibition and working memory compared to moderate-load and control conditions. • Functional near-infrared spectroscopy revealed stronger and more lateralised prefrontal activation, particularly in the right hemisphere, following HRE. • Cognitive benefits from HRE persisted up to 45 minutes post-exercise, especially during high-demand tasks like the 2-back and incongruent Stroop trials. • The study provides novel mechanistic insights into how resistance exercise intensity modulates executive function and prefrontal brain oxygenation.