Normalizing gastrocnemius muscle EMG signal: An optimal set of maximum voluntary isometric contraction tests for young adults considering reproducibility

• Published in: Gait & posture Vol. 82; no. NA; pp. 196 - 202
• Main Authors: Schwartz, Cédric, Wang, François-Charles, Forthomme, Bénédicte, Denoël, Vincent, Brüls, Olivier, Croisier, Jean-Louis
• Format: Journal Article Web Resource
• Language: English
• Published: England Elsevier B.V 01.10.2020; Elsevier
• Subjects: Adult; Electromyography; Electromyography - methods; Female; Gait; Healthy Volunteers; Human health sciences; Humans; Isometric Contraction - physiology; lower limb; Lower limbs; Male; Muscle, Skeletal - physiology; Normalization; Orthopedics, rehabilitation & sports medicine; Orthopédie, rééducation & médecine sportive; Reproducibility of Results; Sciences de la santé humaine; Normalization; Electromyography; Lower limbs; Gait
• ISSN: 0966-6362; 1879-2219; 1879-2219
• DOI: 10.1016/j.gaitpost.2020.08.129

•Three positions are needed to get 90 % of maximal activation for 90 % of the individuals.•Unipodal standing is the more efficient position to obtain a maximal activation.•Five maximal contractions are recommended to obtain a valid maximal activation.•A compromise between maximal activation and reproducibility has to be found. Even though most studies normalize the surface EMG signal of the gastrocnemius muscle using a single position of maximum voluntary isometric contraction (MVIC), several studies tend to indicate that several positions are in fact needed to obtain a maximal voluntary activation (MVA) for most of the subjects. However, no combination of positions has already been described. A combination of MVIC positions to normalize the EMG signal of the gastrocnemius muscle is investigated. the influence of using several positions on the reproducibility of the normalization process is evaluated. Twenty healthy volunteers (45 % female – 55 % male, 25.4 years (SD 4.3), 72.6 kg (SD 13.9), 1.78 m (SD 0.12)) were recruited. Six positions for MVIC were compared and the effect of several normalization combinations on a functional task (gait) was evaluated. Several positions are needed to obtain at least 90 % of the MVA for 90 % of the volunteers even though the use of a single well-chosen position (unipodal standing position with knee fully extended and ankle fully plantar-flexed) will lead to no statistically significant differences of the gait evaluation during stance phase. For each position, five repetitions of the MVIC are recommended to obtain a valid MVA. This study confirms that using several MVIC positions is recommended when possible to normalize the gastrocnemius muscle EMG signal. However, in the situation of a patient where limited MVIC attempts are possible, using a single well-chosen position should not significantly influence the amplitude and the reproducibility of the measures.