Effect of Eccentric Training with Different Durations, Intensities, and Contraction Velocities on Upper Limb Muscle Strength: A Meta-Analysis.

Eccentric training may be more effective for muscle strength, but the optimal duration, intensity, and contraction velocity for improving upper limb strength remain unclear. We conducted a search across four databases (PubMed, Embase, Web of Science, and Cochrane) to evaluate the impact of eccentric training on upper limb skeletal muscle strength. A meta-analysis using standardized mean differences (SMDs) and 95% confidence intervals (CIs) was performed. The results from 11 studies involving 368 participants indicated that eccentric training significantly enhanced upper limb strength (SMD = 0.55, CI: 0.32-0.79). Subgroup analysis showed a slight increase in strength in the 1-4 week period (SMD = 0.38, CI: 0.02-0.73), a significant increase in the 4-8 week period (SMD = 0.69, CI: 0.27-1.10), and a substantial increase at 20 weeks (SMD = 0.71, CI: 0.22-1.21). Moderate intensity showed moderate improvements (SMD = 0.47, CI: 0.18-0.77), while high intensity led to significant adaptations (SMD = 0.70, CI: 0.30-1.10). Rapid eccentric contractions (SMD = 0.70, CI: 0.39-1.02) outperformed slow contractions (SMD = 0.35, CI: -0.01-0.71). Eccentric training is effective, with significant results generally requiring 4-8 weeks of high-intensity rapid eccentric training.