Background: Hamstring strength imbalance between the left and right sides has been identified as a factor contributing to increased injury risk in athletes. However, few studies have evaluated not only bilateral strength differences but also the magnitude of clinically significant imbalances in various hamstring strength parameters. Objective: This study aims to analyze bilateral hamstring muscle asymmetry in terms of maximum, average, and maximum impulse strength, and to evaluate whether the distribution of high imbalances reaches clinically relevant thresholds associated with potential injury risk. Methods: This study is a cross-sectional observational study. Twenty athletes (n = 20) underwent hamstring strength measurements using the NordBord Hamstring Testing System. The parameters analyzed included maximum force, average force, and maximum impulse on the left and right sides. Normality was assessed using the Shapiro–Wilk test. Bilateral comparisons were analyzed using paired t-tests or Wilcoxon signed-rank tests, depending on data distribution, and accompanied by effect size calculations (Cohen's d). Imbalance (%) was calculated for each parameter and classified into low-, moderate-, and high-risk categories. Risk category distribution was analyzed using a binomial test with a clinical reference value of 20%. Result: There were significant bilateral differences in several hamstring strength parameters (p 0.05). Conclusion: Although bilateral hamstring strength differences were found, only maximum impulse imbalance showed clinically relevant significance regarding potential injury risk. These findings emphasize the importance of including impulse analysis, in addition to force, in hamstring injury risk screening using NordBord.
Hanief et al. (Thu,) studied this question.