Abstract: OBJECTIVE: Enhancing sports performance remains a central focus in sports science. Ischemic preconditioning, as a non-pharmacological intervention, has been reported to improve performance. However, the results vary across different studies, and the influencing factors remain unclear. This study aimed to conduct a systematic meta-analysis of original research on ischemic preconditioning combined with exercise, to evaluate its true effects and identify potential moderators.
METHODS: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search was conducted on September 4, 2024, across the Web of Science Core Collection, PubMed, Embase, and CNKI databases using the Mesh keywords “ischemic preconditioning,” “performance,” and “sport.” The inclusion criteria were: (1) studies involving non-clinical populations; (2) sham ischemic preconditioning or non-ischemia treatment as the control for ischemic preconditioning; (3) outcomes including balance, jump performance, strength, accumulated oxygen deficit, power output, maximal repetitions, time trial, time to exhaustion, and oxygen consumption; (4) study designs limited to randomized crossover or randomized controlled trials. Risk of bias was assessed using the Cochrane Risk of Bias 2.0 tool, and the quality of evidence was evaluated with the GRADE approach. Multilevel meta-analyses were conducted using the “meta,” “metafor” and “clubSandwich” packages in R version 4.3.3, along with publication bias tests, subgroup analyses, and meta-regressions.
RESULTS: A total of 90 studies involving 1 439 participants aged 18–70 years were included. Compared with sham ischemic preconditioning or non-ischemia treatment, ischemic preconditioning significantly improved sports performance [effect size (ES)=0.13, 95% confidence interval (CI) (0.06, 0.21), P < 0.01; Q=427; I²-Level 2=0%, I²-Level 3=9.13%, I²-Level 4=5.74%; PI=–0.18 to 0.44; low certainty]. Subgroup analysis revealed that ischemic preconditioning had a greater effect versus blank control than versus sham ischemic preconditioning (P=0.02) [ESCON=0.22, 95% CI (0.12, 0.33], P < 0.01; ESSHAM 0.10, 95% CI (0.02, 0.18), P < 0.01]. (3) No significant between-group differences were found in terms of metabolic characteristics (aerobic/anaerobic), training level, or sex. (4) Among ischemic preconditioning protocols, the 1×5 minutes design showed a significantly greater effect (P=0.01), though it was reported in only one study. Within-subgroup analyses indicated that 3×5 minutes [ES=0.14, 95% CI (0.03, 0.26), P < 0.01] and 4×5 minutes [ES=0.10, 95% CI (0.00, 0.21), P=0.02] were statistically significant. (5) Ischemic preconditioning significantly benefited sedentary participants [ES=0.14, 95% CI (–0.10, 0.39), P=0.03], recreationally active participants [ES=0.15, 95% CI (0.03, 0.27), P=0.02], and participants undergoing general training [ES=0.19, 95% CI (0.04, 0.33), P=0.01], but not highly trained, elite, or world-class athletes. Significant effects were found only in male participants [ES=0.20, 95% CI (0.10, 0.30), P < 0.01]. 
CONCLUSION: Ischemic preconditioning shows a small effect on sports performance, with a significant placebo effect (psychological effect). Ischemic preconditioning protocols (the duration of ischemic preconditioning), particularly protocols of 3×5 minutes or 4×5 minutes, emerge as a key moderating factor. More benefits appear in male participants with low exercise experience, though current evidence does not conclusively support sex, training experience level or age as moderators. Future studies should adopt standardized ischemic preconditioning protocols and rigorously control for placebo effects to better delineate the boundaries and mechanisms underlying the effects of ischemic preconditioning.

Key words: ischemia, strength, blood flow, aerobic capacity, time trial, power output, exhaustion test, exercise, performance, Meta, meta, multilevel meta