Muscle hypertrophy from partial repetition at long vs. short muscle length: A systematic review and meta-analysis

To investigate the regional hypertrophic effects of partial range of motion (ROM) resistance training performed at longer muscle (LL) vs. shorter muscle length (SL). The original protocol (CRD42024626784) was prospectively registered in the PROSPERO database in December 2024. EMBASE, PubMed, Scopus, and LILACS Plus databases were searched up to February 2025. The RoB 2 tool was used to assess risk of bias and quality of evidence. Meta-analyses were performed using robust variance estimation. Eight studies met the inclusion criteria. The muscle groups analyzed included the vastus lateralis (n = 5), rectus femoris (n = 3), vastus medialis (n = 2), vastus intermedius (n = 2), gastrocnemius medialis and lateralis (n = 1 each), and biceps brachii and brachialis (n = 1). Resistance exercise performed at longer muscle length produced significantly greater muscle hypertrophy compared to shorter length (ES = 0.283; CI 0.04–0.52; p = 0.036). Furthermore, regional hypertrophy at both distal (ES = 0.433; CI 0.01−0.85; p = 0.048) and central regions (ES = 0.276; CI 0.01−0.48; p = 0.028) was significantly favored by LL intervention. Resistance training performed at longer muscle length is more effective for promoting overall, distal, and central muscle hypertrophy compared to training at shorter length. This effect appears to be consistent across several muscle groups.