The effects of brain endurance training on physical endurance performance under mental fatigue and non-fatigued conditions: a systematic review and meta-analysis.

BACKGROUND: Mental fatigue impairs physical endurance performance. Brain Endurance Training (BET), which combines cognitive tasks with physical training, may help alleviate these negative effects. PURPOSE: To systematically review and meta-analyze the effects of BET on physical endurance performance under mental fatigue and control (non-fatigued) conditions in athletes and healthy adults. METHODS: This PRISMA 2020-compliant review was registered in PROSPERO (CRD420251036649). PubMed, Web of Science Core Collection, Scopus, and the Cochrane Library were searched from inception through 5 August 2026. Eligible randomized controlled trials compared BET plus physical training with physical training alone in athletes or healthy adults and reported aerobic, anaerobic, or muscular endurance outcomes. Risk of bias was assessed for specific endurance outcomes using RoB 2. Random-effects meta-analyses used standardized mean differences (SMDs) with 95% confidence intervals (CIs), with all effects oriented so that positive values favored BET. Heterogeneity was quantified using I 2, leave-one-out analyses examined influential experiments, and certainty was assessed using GRADE. Funnel plots and Egger's regression were used only as exploratory assessments of small-study effects because each synthesis contained fewer than 10 independent experiments. RESULTS: Ten RCT articles comprising 12 independent experiments were included. Under mental-fatigue conditions, eight independent experiments (n = 275) showed a positive overall effect of BET on endurance performance (SMD = 0.82, 95% CI 0.33 to 1.30; p = 0.001; I 2 = 69%). Under non-fatigued conditions, nine independent experiments (n = 315) yielded an imprecise and highly heterogeneous estimate (SMD = 0.73, 95% CI -0.03 to 1.49; p = 0.058; I 2 = 89%). A formal moderator test did not identify a statistically significant difference between test states (contrast = 0.59, 95% CI -0.30 to 1.48; p = 0.120). Overall RoB 2 judgments raised some concerns, and GRADE certainty ranged from very low to moderate. CONCLUSIONS: BET may improve endurance performance after mental-fatigue induction, although the magnitude remains uncertain. Evidence under non-fatigued conditions is inconclusive, and the formal moderator test did not confirm a difference between test states. Larger independent trials with prespecified outcomes and complete reporting are needed. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251036649, identifier: CRD420251036649.