Context: Soccer players often have a dominant (D) leg, which could influence the relative strength between the quadriceps and hamstrings. The hamstring-to-quadriceps (H:Q) ratio can be assessed on a dynamometer at various velocities to provide information on injury risk.
Objective: To assess the concentric hamstrings and concentric quadriceps strength ratio (conventional H:Q ratio) assessed in D and nondominant (ND) legs at various speeds in male soccer players.
Data sources: A systematic literature search was completed from inception to 2020 in PubMed, Academic Search Ultimate, CINAHL, and SPORTDiscus.
Study selection: Keywords associated with the H:Q ratio were connected with terms for soccer players. Titles and abstracts were screened by 2 reviewers based on inclusion and exclusion criteria related to sex, playing level, language, and measurement. A total of 81 studies were reviewed and 17 studies (21%) were used.
Study design: A meta-analysis with random effects modeling generated standardized mean differences with 95% CIs between legs and speeds.
Level of evidence: Level 3.
Data extraction: A total of 38 cohorts were identified, with 14, 13, and 11 cohorts assessed at low, intermediate, and high velocities, respectively. The Quality Assessment Tool for Observational Cohort and Cross-sectional Studies from the National Institutes of Health was used.
Results: The mean H:Q ratio at low velocities was 59.8 ± 9.5% in D leg and 58.6 ± 9.9% in ND leg, 64.2 ± 10.7% (D) and 63.6 ± 11.3% (ND) at the intermediate velocity, and 71.9 ± 12.7% (D) and 72.8 ± 12.7% (ND) at the high velocity. Low, intermediate, and high velocities had small effects of 0.13, 0.10, and -0.06, respectively.
Conclusion: Conventional H:Q ratios vary across velocities but did not differ between D and ND limbs in male soccer players. This study may provide the foundation to establish norms and clinically meaningful differences.
Keywords: asymmetry; hamstrings; quadriceps; soccer.