Heat Acclimation with Blood Flow Restriction Improves Cognitive-Motor Dual-Task Ability and Neuromuscular Fatigue

This study examined whether heat acclimation (HA), and HA with blood flow restriction (BFR) could attenuate cognition and neuromuscular function impairments in cognitive-motor dual-task (CMDT) during exercise-heat stress. Twenty trained adults were randomly assigned to one of two HA protocols over six sessions (~8 days). Each session consisted of 4 × 8-min self-regulated cycling intervals (5-min "strong effort", 3-min "moderate effort") in temperate conditions (20°C), immediately followed by 40-min hot water immersion (40°C). One group exercised with BFR during the "strong" bouts (50% arterial occlusion pressure; BFR_HA), whereas the control group completed without occlusion (CTRL_HA). Before and after HA protocols, participants completed an exercise-heat stress test with CMDT (pre- post-HA; 40°C, 40% relative humidity): 1 × 7-min self-regulated cycling ("strong effort") followed by 2 × 7-min fixed-power blocks with an attentional task. Heart rate, rectal temperature, and mental effort were recorded, while neuromuscular function (peripheral, central responses) was assessed post-CMDT during a 1-min sustained maximal contraction. During HA sessions, heart rate and rectal temperature were comparable between groups (p ≥ 0.19), despite a reduced power during BFR_HA (-22% ± 6%; p < 0.001). Post-HA, both groups reduced (p ≤ 0.003) peak heart rate (CTRL_HA:-5 ± 4 bpm, BFR_HA:-7 ± 6 bpm) and rectal temperature (CTRL_HA:-0.19 ± 0.15°C, BFR_HA:-0.15 ± 0.12°C). Both improved attentional performance (CTRL_HA:+10% ± 5%, BFR_HA:+9% ± 7%; p < 0.001) with lower mental effort, while reduced force loss was evident only in BFR_HA post-HA (+18% ± 12%, p = 0.001), consistent with lower central fatigue (p = 0.028) versus pre-HA. Effective heat adaptations were induced by both HA protocols, despite the lower workload with BFR. Both approaches enhanced sustained attention during an exercise-heat stress with CMDT, while BFR additionally mitigated central fatigue.