Physiological adaptations and performance enhancement with combined blood flow restricted and interval training: A systematic review with meta-analysis

Purpose: We aimed to determine: (a) the chronic effects of interval training (IT) combined with blood flow restriction (BFR) on physiological adaptations (aerobic/anaerobic capacity and muscle responses) and performance enhancement (endurance and sprints), and (b) the influence of participant characteristics and intervention protocols on these effects. Methods: Searches were conducted in PubMed, Web of Science (Core Collection), Cochrane Library (Embase, ClinicalTrials.gov, and International Clinical Trials Registry Platform), and Chinese National Knowledge Infrastructure on April 2, with updates on October 17, 2024. Pooled effects for each outcome were summarized using Hedge's g (g) through meta-analysis-based random effects models, and subgroup and regression analyses were used to explore moderators. Results: A total of 24 studies with 621 participants were included. IT combined with BFR (IT+BFR) significantly improved maximal oxygen uptake (VO_2max) (g = 0.63, I² = 63%), mean power during the Wingate 30-s test (g = 0.70, I² = 47%), muscle strength (g = 0.88, I² = 64%), muscle endurance (g = 0.43, I² = 0%), time to fatigue (g = 1.26, I² = 86%), and maximal aerobic speed (g = 0.74, I² = 0%) compared to IT alone. Subgroup analysis indicated that participant characteristics including training status, IT intensity, and IT modes significantly moderated VO_2max (subgroup differences: p < 0.05). Specifically, IT+BFR showed significantly superior improvements in VO_2max compared to IT alone in trained individuals (g = 0.76) at supra-maximal intensity (g = 1.29) and moderate intensity (g = 1.08) as well as in walking (g = 1.64) and running (g = 0.63) modes. Meta-regression analysis showed cuff width (β = 0.14) was significantly associated with VO_2max change, identifying 8.23 cm as the minimum threshold required for significant improvement. Subgroup analyses regarding muscle strength did not reveal any significant moderators. Conclusion: IT+BFR enhances physiological adaptations and optimizes aspects of endurance performance, with moderators including training status, IT protocol (intensity, mode, and type), and cuff width. This intervention addresses various IT-related challenges and provides tailored protocols and benefits for diverse populations.