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

Background Recurrent hamstring strain injuries are associated with deficits in eccentric strength and altered muscle-tendon extensibility, which may persist and contribute to reinjury risk. Objective To 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. Methods Fifty-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). Results Mean ± 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 ( r = -0.65 [95% CI −0.78 to −0.46], p < 0.001) and weakly in the non-dominant limb ( r = –0.34 [95% CI −0.56 to −0.06], p = 0.02). No significant correlation was observed between flexibility and the H:Q ratio ( p = 0.38). Flexibility remained an independent predictor of the Con:Ecc ratio after adjusting for age (β = –0.61, p < 0.001; R 2 = 0.38). Conclusions Reduced 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.