Effect of blood-flow restricted vs heavy-load strength training on muscle strength: Systematic review and meta-analysis.

INTRODUCTION: Heavy-load strength training (HLT) is generally considered the Gold Standard exercise modality for inducing gains in skeletal muscle strength. However, use of heavy external exercise loads may be contraindicative in frail individuals. Low-load resistance exercise combined with partial blood-flow restriction (LL-BFR exercise) may offer an effective alternative for increasing mechanical muscle strength and size. The aim of this study was to compare the effect of LL-BFR training to HLT on maximal muscle strength gains. Prospero registration-id (CRD42014013382). MATERIALS AND METHODS: A systematic search in six healthcare science databases and reference lists was conducted. Data selected for primary analysis consisted of post-intervention changes in maximal muscle strength. A random-effects meta-analysis with standardized mean differences (SMD) was used. RESULTS: Of 1413 papers identified through systematic search routines, sixteen papers fulfilled the inclusion criteria, totalling 153 participants completing HLT and 157 completing LL-BFR training. The magnitude of training-induced gains in maximal muscle strength did not differ between LL-BFR training and HLT (SMD of -0.17 (95% CI: -0.40; 0.05)). Low between-study heterogeneity was noted (I2  = 0.0%, Chi2 P = 9.65). CONCLUSION: Low-load blood-flow-restricted training appears equally effective of producing gains in maximal voluntary muscle strength compared to HLT in 20- to 80-year-old healthy and habitually active adults.