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. 2022 Mar-Apr;14(2):246-253.
doi: 10.1177/19417381211011407. Epub 2021 Apr 28.

Comparison of Electromyographic Activity During Hip Extension Exercises Under Gravitational or Inertial Loading Conditions

Rodrigo Martín-San Agustín  1 , Lorenzo Castillo-Ballesta  1 , Javier Llobat Sancho  2 , Rubén Esbri-Navarro  1 , Mariana Sánchez-Barbadora  1
Affiliations

Comparison of Electromyographic Activity During Hip Extension Exercises Under Gravitational or Inertial Loading Conditions

Rodrigo Martín-San Agustín et al. Sports Health. 2022 Mar-Apr.

Abstract

Background: Hamstring injury prevention programs include strengthening, especially eccentric exercises using both gravitational and inertial loading. Inertial exercises are characterized by eccentric contractions of high intensity and velocity. This study aimed to analyze the muscular activation of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (GM), and gracilis (GC) muscles during hip extension (HE) exercises performed under both gravitational and inertial loading conditions.

Hypothesis: Inertial training would generate a greater activation of HE muscles than gravitational training.

Study design: Cross-sectional study.

Level of evidence: Level 4.

Methods: Fifteen resistance-trained men performed the unilateral straight knee bridge (SKB), 45° of HE, and stiff-leg deadlift (SDL) exercises under gravitational and inertial loading conditions. Concentric and eccentric phases were identified with a linear encoder. Differences between load types, exercises, and their interaction were examined to establish the electromyographic (EMG) activity of each muscle and BF/ST ratio.

Results: In the concentric phase, inertial loading showed a higher normalized EMG than gravitational loading for BF, ST, and GM. SKB and HE activated BF and ST between 9.6% and 24.3% more than SDL. In the eccentric phase, the inertial modality achieved greater GM activation than the gravitational form (18.1%). BF activation was increased with HE and SKB as compared with SDL (24.4% and 16.4%, respectively), while ST activation was likewise enhanced with HE as compared with SDL (15.1%).

Conclusion: Inertial training is more effective than gravitational training for the concentric activation of the hamstring muscles while SDL showed lower hamstring activation than HE and SKB. Therefore, HE and SKB with inertial loading should be taken into account in hamstring training programs.

Clinical relevance: Inertial training is more effective than gravitational training for the concentric activation of the hamstring muscles. HE and SKB with inertial loading should be taken into account in hamstring training programs.

Keywords: iso-inertial; muscle power; physiology; resistance training.

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Conflict of interest statement

The authors report no potential conflicts of interest in the development and publication of this article.

Figures

Figure 1.
Figure 1.
Unilateral straight knee bridge: gravitational (A) and inertial (B).
Figure 2.
Figure 2.
Forty-five degrees of hip extension: gravitational (A) and inertial (B).
Figure 3.
Figure 3.
Bilateral stiff-leg deadlift: gravitational (A) and inertial (B).
Figure 4.
Figure 4.
Biceps femoris (BF) to semitendinosus (ST) nEMG relationship for the (A) concentric and (B) eccentric phases of each exercise and modality. Exercises to the left of and above the 45° line exhibited higher levels of BF than ST nEMG. HE, 45° of hip extension; nEMG, normalized electromyography; SDL, bilateral stiff-leg deadlift; SKB, unilateral straight knee bridge. *Differences between gravitational and inertial (P ≤ 0.05). †Significant differences compared to gravitational HE. ‡Significant differences compared to gravitational SDL (P ≤ 0.05).
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References

    1. Agustín RM-S, Sánchez-Barbadora M, García-Vidal JA. Validity of an inertial system for measuring velocity, force, and power during hamstring exercises performed on a flywheel resistance training device. Peer J. 2020;8:e10169. - PMC - PubMed
    1. Andersen V, Fimland MS, Mo DA, et al.. Electromyographic comparison of barbell deadlift, hex bar deadlift, and hip thrust exercises: a cross-over study. J Strength Cond Res. 2018;32:587-593. - PubMed
    1. Askling C, Karlsson J, Thorstensson A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports. 2003;13:244-250. - PubMed
    1. Bourne MN, Duhig SJ, Timmins RG, et al.. Impact of the Nordic hamstring and hip extension exercises on hamstring architecture and morphology: implications for injury prevention. Br J Sports Med. 2017;51:469-477. - PubMed
    1. Bourne MN, Opar DA, Williams MD, Najjar AA, Shield AJ. Muscle activation patterns in the Nordic hamstring exercise: impact of prior strain injury. Scand J Med Sci Sports. 2016;26:666-674. - PubMed