Author(s): SHIOZAWA, J., HITOSHI, A., MORIO, H., IKEDA, H., ISHIJIMA, M., TAKAZAWA, Y., Institution: JUNTENDO UNIVERSITY, Country: JAPAN, Abstract-ID: 2018

INTRODUCTION:
Hamstring strain injuries (HSI) are a common problem in football, accounting for 12% of all injuries in high-level professional players, and recurrence rates have not decreased in recent years. These data suggest that our understanding of HSI and the risk of re-injury is incomplete. Many risk factors for HSI have been reported, such as older age, previous HSI and muscle fatigue. In recent years, eccentric hamstring imbalances, low eccentric strength and torque have been highlighted as new risk factors for HSI in many athletes. However, it has remained unclear whether eccentric hamstring imbalances, low eccentric strength and torque are associated with a previous occurrence of HSI in football players. The aim of this study was to investigate the relationship between the occurrence of HSI and eccentric hamstring strength in Japanese male soccer players.
METHODS:
A total of 119 elite male football players (mean age 25.5± 3.5 years) from one team underwent eccentric strength testing during the preseason (2020-2024). Players with a history of HSI were assigned to group H (mean age 25.8± 3.3 years) and those without a history of HSI to group NH (mean age 25.5± 3.5 years). Eccentric hamstring strength was measured using the NordBord (VALD Performance, Albion, Australia). From these measurements, maximum force (N), torque (N･m), and imbalances for each leg (%) were calculated. All data were analyzed using SPSS Statistics software version 21.0 (IBM, Armonk, NY). p-value <0.05 was considered statistically significant.
RESULTS:
The number of players with a history of HSI was thirty-six (30.3%: group H) and those without a history of HSI was eighty-three (69.7%: group NH). There were no significant differences in baseline characteristics such as age, weight, height and body mass index (BMI) between the two groups. No significant differences were observed between group H (dominant leg: 309± 64 N, non-dominant leg: 299± 63 N) and group NH (dominant leg: 308± 61 N, non-dominant leg: 291± 60 N) in the maximum force of eccentric hamstring strength (p＝0. 821, p＝0.821) and torque between group H (dominant leg: 134±27 N･m, non-dominant leg: 130±26 N･m) and group NH (dominant leg: 137±28 N･m, non-dominant leg: 130±28 N･m), respectively (p＝0.810, p＝0.958). In addition, the eccentric hamstring force imbalances for each leg were not significantly different between the two groups (group H: 6.2± 6.4, group NH: 7.4± 7.7) (p=0.387).
CONCLUSION:
The history of HSI among elite male soccer players in Japan was approximately thirty percent. There was no association between a history of HSI and eccentric hamstring strength.