Vol 15, Issue 1

Electromyographic Examination of Hip and Knee Extension Hex Bar Exercises Varied by Starting Knee and Torso Angles

January 1, 2022 - By 

Authors

Edward Jo, California State Polytechnic University, Pomona
Kevin A. Valenzuela, California State University, Pomona
Whitney Leyva
Jennifer Rivera
Kalin Tomlinson
Elisabeth Zetiz
International Journal of Exercise Science 15(1): 541-551, 2022.
DOI: 10.70252/VOIZ8043

Abstract

Variations of the deadlift can be executed using the hexagonal (hex) bar by altering, for instance, the knee and torso angles while maintaining a constant hip angle at the start position. PURPOSE: To examine muscle activation patterns of the biceps femoris, rectus femoris, and erector spinae during three deadlift variations using the hex bar. METHODS: Twenty resistance-trained male and female subjects performed hex bar deadlift variations in three different starting knee flexion positions: 128.4 ± 8.5°, 111.9 ± 8.7°, and 98.3 ± 6.5°. Subjects performed three repetitions at 75% of their three-repetition maximum. Electromyography sensors were placed on the dominant biceps femoris, rectus femoris, and lumbar erector spinae. A one-way repeated measures ANOVA was used to detect differences in mean and peak EMG values normalized to maximum voluntary isometric contraction (MVIC) (p < 0.05). RESULTS: As knee flexion increased at the starting position, mean activation of the rectus femoris increased (24.7 ± 21.5  35.5 ± 25.4  62.1 ± 31.3% MVIC, p < 0.001), while biceps femoris (40.6 ± 17.9  34.0 ± 16.4  28.1 ± 14.5% MVIC, p = 0.003) and erector spinae (73.0 ± 27.6  65.9 ± 34.4  54.9 ± 32.5% MVIC, p = 0.009) activation decreased. Peak activation of the rectus femoris increased (46.9 ± 33.0  60.9 ± 38.7  99.3 ± 41.6% MVIC, p < 0.001) while decreasing in the erector spinae (118.6 ± 47.1  105.9 ± 49.4  89.1 ± 40.1% MVIC, p = 0.008). The rectus femoris experienced the greatest mean differences of the three muscles. CONCLUSIONS: Practitioners should consider the muscular goals when adjusting the starting position of a hex bar deadlift as posterior chain recruitment diminished and quadriceps activation increased as knee flexion increased.

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