Proposal of an alternative method to find out the break-point in nordic hamstring exercise: a pilot study

Aim: Nordic Hamstring Exercise (NHE) is a well known exercise used to eccentrically train the hamstring muscles. Sometimes it is also used as a test for injury prevention but the measurement modalities are poor1,2. This study proposes an alternative method to measure the "break-point" (BK) during the NHE movement. Method: Twelve female young national basketball players (16±0 yrs; 176±7.8 cm; 67.9±9.9 kg) were filmed at 30fps (Casio FH20, Shibuva, Tokyo, Japan) during a NHE training session. Each subject performed three NHE and the best was chosen for the analysis. Three static markers were applied on the lateral malleolus, lateral knee and trochanter of the right leg for the video analysis (Dartfish 6.0, Fribourg, Switzeland). For each NHE it was measured the dynamic posterior angle of the knee and it was exported and analyzed with a time/angle diagram. The data were elaborated with an algorithm to find out the BK in which the subjects lost the control of the exercise falling frontward. Results: The average time of the NHE was 2.3±0.5s, the BK arrived at 69% of the movement after 1.6±0.5s. The average BK arrived after 17.3±2.8° of movement although the 58% of the subjects maintained a correct alignment after 30° of movement. Conclusion: The used algorithm allows to discriminate the dynamic BK starting from the posterior angle of the knee. These results avoid the observation process used in other evaluation protocols of the NHE1,2. Further studies on the algorithm and its validity are needed. References 1. Engebretsen AH et al. (2010). Am J Sports Med 38(6):1147-53. 2. Sconce E (2015). J Sport Rehabil 24(1):13-20.