Effect of eccentric strengthening on hamstring strength: a Meta-analysis
Zheng Wei1, Sun Libing1, Xiong Yingzhe2, Zhang Yichi3, You Jing1, Huang Wenqi1, Guo Yanhua1, Liu Hongjun1
1Tianjin University of Sport, Tianjin 301617, China; 2Tsinghua University, Beijing 100084, China; 3Univerisy College London, London WC1N 1AX, UK
Abstract: OBJECTIVE: The evaluation indexes for hamstring strength improved by eccentric strengthening are scattered and the results are not consistent. Herein, a Meta-analysis is conducted to analyze the influence of eccentric training on hamstring strength, aiming to provide an evidence-based basis for improving the effect of sports training and applying reasonable and effective strategies for injury protection.
METHODS: Randomized controlled trials on hamstring strength improved by eccentric strengthening were searched from CNKI, WanFang, PubMed, Web of Science, and EBSCO databases. The retrieval period was from database building to September 2021. Review manager 5.3 and Stata 16.0 were used for quality assessment, Meta-analysis, subgroup analysis, sensitivity analysis, and publication bias analysis.
RESULTS: A total of 14 articles involving 557 subjects were included, with 314 subjects in experimental group and 243 subjects in control group. The overall quality of literature was high. Eccentric strengthening can be used as an effective intervention to significantly improve the relative concentric contraction peak torque [standardized mean difference (SMD)=0.60, 95% confidence interval (CI): 0.18-1.02, P < 0.01] and eccentric contraction peak torque of the hamstrings (SMD=0.43, 95% CI: 0.18-0.67, P < 0.001) and functional H/Q ratio (SMD=0.69, 95% CI: 0.34-1.05, P=0.000 1), but it has no significant effect on isometric contraction peak torque and conventional H/Q ratio. The relative concentric contraction peak torque (SMD=0.86, 95% CI: 0.22-1.49, P < 0.01) and the relative eccentric contraction peak torque (SMD=0.46, 95% CI: 0.09-0.82, P < 0.05) in the experimental group were significantly different from those in the control group when a low angular velocity was selected. The 6-week eccentric strengthening was better than the 4- and 27-week eccentric strengthening to improve the functional H/Q ratio (SMD=0.71, 95% CI: 0.32-1.10, P < 0.001).
CONCLUSION: Eccentric strengthening can improve hamstring strength, characterized by increasing hamstring concentric and eccentric contraction strength, correcting the strength imbalance of hamstring and quadriceps, and reducing initial or second injuries of the hamstring.
Key words: eccentric strengthening, muscle strength, hamstring, quadriceps, Meta-analysis