The Effect of the Nordic Hamstring Exercise on Hamstring Muscle Activity Distribution During High-Speed Running Estimated Using Multichannel Electromyography: A Pragmatic Randomized Controlled Trial.

Objective: To evaluate the effect of the Nordic hamstring exercise on normalized muscle activity and relative contribution of the biceps femoris long head, semitendinosus, and semimembranosus through multichannel electromyography in the late-swing phase of high-speed running.

Design: A pragmatic, 2-arm, single-center randomized controlled trial. Participants were randomly assigned to a Nordic group or control group.

Setting: Dutch male basketball.

Participants: Twenty injury-free players (mean age 18 ± 3 years).

Intervention: A 12-week Nordic hamstring exercise intervention.

Main Outcome Measures: Level of normalized muscle activity (percentage maximal voluntary isometric contraction [%MVIC]) and relative contribution (%con) of hamstring muscles for 12 weeks.

Results: The Nordic hamstring exercise intervention did not result in significant changes for 12 weeks. For normalized muscle activity, between-group differences (compared with the control group) for 12 weeks were 11.4 %MVIC (95% confidence interval [95% CI]: -11.0, 33.8) for the biceps femoris long head, -9.4 %MVIC (95% CI: -23.3, 5.2) for the semitendinosus, and -2.7 %MVIC (95% CI: -15.8, 10.3) for the semimembranosus, P = 0.151. For relative contribution, between-group differences for 12 weeks were -6.1 %con (95% CI: -2.4, 14.6) for the biceps femoris long head, -7.0 %con (95% CI: -13.6, -0.4) for the semitendinosus, and 0.9 %con (95% CI: -9.2, 11.0) for the semimembranosus P = 0.187. Positive values are in favor of the Nordic group.

Conclusions: A 12-week Nordic hamstring exercise intervention did not affect the level of muscle activity and relative contribution of hamstring muscles in the late-swing phase of high-speed running. Because of the low amount of data sets, results should be interpreted cautiously.