No relationship between the nordic hamstring and two different isometric strength tests to assess hamstring muscle strength in professional soccer players

Objectives: To investigate the relationship between one eccentric and two isometric tests commonly used to assess hamstring strength in professional soccer. Settings: Professional soccer club. Design: Cross-sectional study. Participants: Twenty male professional soccer players. Main outcome measures: Hamstring force was quantified during 3 tests (Nordic hamstring eccentric, 90:20 isometric posterior-chain strength and isometric 15 degrees knee flexion) using a load cell, a handheld dynamometer and a force platform, respectively. Results: Poor relationships and low concordance were observed between isometric and eccentric tests, showing different ability to discriminate hamstring weakness and asymmetries. The Nordic hamstring test identified between-limb asymmetry >15% in 30% of the players, 25% in the 15 degrees knee flexion and 5% in the 90:20 test. All players obtained different results in the three tests with only one showing asymmetry >15% in two tests. Conclusion: Results obtained in each test cannot inform the others. Mechanical outputs of these tests must be used for particular purposes during the prevention, rehabilitation and monitoring process of hamstring injury. Isometric testing might be preferable during the initial phases of the recovery process of a hamstring injury while the Nordic hamstring test might be used in the last stages or detect muscle weakness/asymmetries in non-injured players. (c) 2020 Elsevier Ltd. All rights reserved.