Blood flow restriction during heat acclimation reduces force loss in trained adults

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), whereas the control group completed without occlusion (CTRL). 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 (-22% ± 6%; p < 0.001). Post-HA, both groups reduced (p ≤ 0.003) peak heart rate (CTRL:-5 ± 4 bpm, BFR:-7 ± 6 bpm) and rectal temperature (CTRL:-0.19 ± 0.15°C, BFR:-0.15 ± 0.12°C). Both improved attentional performance (CTRL:+10% ± 5%, BFR:+9% ± 7%; p < 0.001) with lower mental effort, while reduced force loss was evident only in BFR 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.