Muscle activation during maximum voluntary contraction and m-wave related in healthy but not in injured conditions: Implications when normalizing electromyography. (October 2019)

• Record Type: Journal Article
• Authors: Zellers, Jennifer A.; Parker, Sheridan; Marmon, Adam; Grävare Silbernagel, Karin
• Is Part Of: Clinical biomechanics. Volume 69(2019)
• Page Start: 104
• Page End: 108
• Publication Date: 2019-10
• Subjects: Achilles -- Rupture -- Muscle -- Recruitment -- Inhibition; Biomechanics -- Periodicals; Osteopathic medicine -- Periodicals; Biomechanics -- Periodicals; Osteopathic Medicine -- Periodicals; 612.76
• DOI: 10.1016/j.clinbiomech.2019.07.007
• Languages: English
• ISSNs: 0268-0033

Abstract

Abstract: Background: Electromyography signal amplitude is influenced by a variety of factors. Normalization strategies aimed at decreasing signal variability include using peak electromyography signal during a maximum voluntary contraction and peak-to-peak M-wave amplitude. However, whether these normalization methods are comparable has not been investigated in injured populations. This study investigated the relationship between peak signal during maximum voluntary contraction and M-wave amplitude in individuals with a unilateral Achilles tendon rupture. Secondarily, we observed whether the two normalizations strategies would yield similar results when evaluating between limb differences in muscle activity during a jump task. Methods: Eleven individuals 1–3 years after a unilateral Achilles tendon rupture were included in this study. Surface electromyography was used on the medial and lateral gastrocnemii bilaterally. Peak maximum voluntary contraction, M-wave amplitude, and electromyography during a jumping task were collected. Findings: A strong relationship was observed between peak maximum voluntary contraction and M-wave amplitude on the uninjured ( r = 0.71–0.88, P < 0.05) but not on the ruptured side ( r = 0.41–0.44, P > 0.05). The two normalization techniques did not produce different results when comparing the uninjured and ruptured sides. Interpretation: The findings of this study suggest that M-wave normalization yields similar results as peak maximum voluntary contraction-normalized electromyography in uninjured conditions. M-wave normalization may be a useful strategy in an injured population where a maximal muscle contraction is unsafe or impaired. Highlights: Normalizing electromyography in individuals with muscle inhibition is challenging. M-wave normalization may be useful but has mostly been studied in healthy normals. We measured maximum voluntary contraction and M-wave in people with Achilles repair. Maximum voluntary contraction and M-wave were related only on the uninjured side. M-wave is preferable to normalize electromyography in populations with concern for inhibition.