Difference of Hamstring Activity Between Bilateral and Unilateral Nordic Hamstring Exercises With a Sloped Platform

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Medicine

Background:

• The Nordic hamstring exercise (NHE) is commonly used to strengthen the hamstring muscles.
• Understanding the electromyographic (EMG) differences between bilateral and unilateral NHE variations is crucial for optimizing training and injury prevention strategies.

Purpose of the Study:

• To compare the EMG activity of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during bilateral and unilateral NHE on a sloped platform.
• To determine the effect of different platform angles on muscle activation and joint angles during NHE variations.

Main Methods:

• A case-control study involving 14 male participants.
• Participants performed three variations of NHE: bilateral (N40) and unilateral (N40U) at 40°, and unilateral (N50U) at 50° on a sloped platform.
• EMG activity of BFlh and ST, and knee flexion angles were recorded and analyzed (%MVIC, angle at peak BFlh EMG, and break-point angle).

Main Results:

• Unilateral NHE (N40U and N50U) elicited significantly higher BFlh %MVIC compared to bilateral NHE (N40).
• Significant differences in BFlh and ST %MVIC were observed between the two unilateral NHE variations (N40U vs. N50U).
• The break-point angle and angle at peak BFlh EMG were consistently below 30° across all NHE variations.

Conclusions:

• Unilateral NHE demonstrates greater activation of the biceps femoris long head compared to bilateral NHE.
• The findings suggest that unilateral NHE may serve as a more specific exercise for hamstring injury prevention, particularly considering the high BFlh activity during the late swing phase of running.