Lack of Effect of Ankle Position During the Nordic Curl on Muscle Activity of the Biceps Femoris and Medial Gastrocnemius

Context: Regular performance (similar to 2x/wk) of Nordic curls has been shown to increase hamstring strength and reduce the risk of hamstring strain injury, although no consensus on ankle position has been provided. Objective: To compare the effects of performing Nordic curls, with the ankle in a dorsiflexed (DF) or plantar-flexed (PF) position, on muscle activity of the biceps femoris (BF) and medial gastrocnemius (MG). Participants: 15 male college athletes (age 22.6 +/- 2.1 y, height 1.78 +/- 0.06 m, body mass 88.75 +/- 8.95 kg). Design: A repeated-measures design was used, with participants performing 2 sets of 3 repetitions of both variations of Nordic curls, while muscle activity was assessed via surface electromyography (EMG) of the BF and MG. Comparisons of muscle activity were made by examining the normalized EMG data as the percentage of their maximum voluntary isometric contraction. Results: Paired-samples t test revealed no significant difference in normalized muscle activity of the BF (124.5%+/- 6.2% vs 128.1 +/- 5.0%, P >.05, Cohen d = 0.64, power = .996) or MG (82.1%+/- 3.9% vs 83.5 +/- 4.8%, P >.05, Cohen d = 0.32, power = .947) during the Nordic curls in a PF or DF position, respectively. Conclusion: Ankle position does not influence muscle activity during the Nordic curl; however, performance of Nordic curls with the ankle in a DF position may be preferential, as this replicates the ankle position during terminal leg swing during running, which tends to be the point at which hamstring strains have been reported.