Eight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrations

Exercise and heat stress have been reported to independently provide benefits to brain health. We tested the hypothesis that 8 weeks of post-exercise local heating, passive local heating only, or exercise training only improves cognitive performance compared to a control group. Sixty young, healthy participants (n = 30 female, age: 23 [3] years) were randomised into one of four groups: control (CON), aerobic exercise (EX), local heating (HEAT), or combined heat and exercise (HEATEX). Participants completed supervised sessions three times per week for 8 weeks. Exercise sessions were completed at 70-75% of maximum heart rate on a cycle ergometer, and local heating sessions involved hot water immersion (42°C) of the feet (both 45 min duration). The HEATEX group performed both the EX and HEAT components sequentially in the same session (90 min total duration). Cognitive performance was measured at baseline and at the end of the 8-week intervention using the digit symbol substitution task (DSST) and the Stroop test. There was a main effect of time (P < 0.001) where DSST performance improved; however, there was no group effect (P = 0.089) or time by group interaction (P = 0.119). There was no effect of the interventions on Stroop cost (baseline: 90 [SD: 70] ms; post-intervention: 84 [SD: 70] ms; time by condition interaction P = 0.205). Similarly, there were no effects of the interventions on circulating plasma concentrations of brain-derived neurotrophic factor (interaction P = 0.189). Eight weeks of exercise training and/or local heating is not sufficient to improve cognitive performance in young, moderately fit individuals.