Relationship between hamstring flexibility (askling H-test) and isokinetic strength ratios in elite soccer players with prior hamstring strain injury: A cross-sectional study.

Abstract

BackgroundRecurrent hamstring strain injuries are associated with deficits in eccentric strength and altered muscle-tendon extensibility, which may persist and contribute to reinjury risk.ObjectiveTo examine the relationship between hamstring flexibility, assessed by Askling H-test, and isokinetic strength ratios; concentric-to-eccentric (Con:Ecc) and hamstring-to-quadriceps (H:Q) in elite soccer players with previous hamstring strain.MethodsFifty-two male professional players (27 ± 5 years) with clinically confirmed prior hamstring injury completed the Askling H-test and bilateral isokinetic testing at 60°·s⁻¹ (concentric) and 180°·s⁻¹ (eccentric). The mean of three maximal efforts was used to calculate peak torques. Pearson correlations and multiple linear regression examined the relationship between flexibility, age, and strength ratios (α = 0.05).ResultsMean ± SD Con:Ecc ratio was 86 ± 9% and H:Q ratio 63 ± 7%. Hamstring flexibility correlated inversely with the Con:Ecc ratio, moderately in the dominant limb (<i>r</i> = -0.65 [95% CI -0.78 to -0.46], <i>p</i> < 0.001) and weakly in the non-dominant limb (<i>r</i> = -0.34 [95% CI -0.56 to -0.06], <i>p</i> = 0.02). No significant correlation was observed between flexibility and the H:Q ratio (<i>p</i> = 0.38). Flexibility remained an independent predictor of the Con:Ecc ratio after adjusting for age (β = -0.61, p < 0.001; R² = 0.38).ConclusionsReduced hamstring flexibility is associated with a higher Con:Ecc ratio, indicating relatively reduced eccentric capacity, but is not related to H:Q balance. These findings highlight the role of flexibility in hamstring strength balance and warrant longitudinal investigation.