768 FO30 – Hamstring muscle elasticity in elite athletes with and without a previous hamstring strain injury

Background Hamstring strain injuries (HSI) are prevalent in elite sports. Monitoring for (re-)injury prevention often includes tests such as the straight-leg-raise, reflecting the stiffness of all the tissues crossing the hip joint. Alternatively, ultrasound shear wave elastography (SWE) allows to assess the regional shear modulus (index of elasticity) of individual hamstring muscles. SWE can be particularly useful during the post-injury regeneration process, where fibrous (scar) tissues that stiffen the injured area are formed, potentially contributing to the risk of re-injury. Objective To assess the impact of a previous muscle injury on local muscle elasticity in elite athletes. Design Cross-sectional study. Setting One-time measurement in elite athletes. Participants 136 elite athletes (80 men, 56 women) in fencing, figure skating, soccer, track and field, basketball, taekwondo, field hockey, rugby7, bobsleigh. 37 suffered from a previous unilateral HIS. The rest had no previous HSI. Main outcomes measurements Injury history was collected according to international standards in collaboration with the athlete's medical staff. The elasticity of the biceps femoris long head (BF), semitendinosus (ST) and semimembranosus (SM) was assessed using SWE. Linear mixed models were used to compare muscle elasticity with limb (injured, non-injured side) and athletes (injured, healthy) as fixed factors. Results HIS repartition among the 37 reported: 28 (76%) on BF, 5 (13%) on SM and 4 (11%) on ST. No significant differences between injured and non-injured limb (P=0.50; inter-limb difference = -0.13±2.99 KPa for ST, 0.40±6.08 KPa for SM and -0.61±5.60 KPa for BF). and between the injured and non-injured athletes (P=0.76) were observed. Conclusions HSI history does not seem to be associated with altered elasticity in elite athletes. These results invalid the hypothesis that the inclusion of collagen post-injury would increase muscle stiffness. Further research using advanced post-processing method to quantify SWE propagation velocity in the injured area are required.