Global electromyographic signal characteristics depend on maximal isometric contraction method in the knee extensors. (October 2018)

• Record Type: Journal Article
• Authors: Tomko, Patrick M.; Colquhoun, Ryan J.; Magrini, Mitchel A.; Muddle, Tyler W.D.; Jenkins, Nathaniel D.M.
• Is Part Of: Journal of electromyography and kinesiology. Volume 42(2018)
• Page Start: 111
• Page End: 116
• Publication Date: 2018-10
• Subjects: MVIC -- EMG normalization -- Voluntary activation -- Muscle activation; Electromyography -- Periodicals; Kinesiology -- Periodicals; Electromyography -- Periodicals; Movement -- physiology -- Periodicals; Muscles -- physiology -- Periodicals; Électromyographie -- Périodiques; Cinésiologie -- Périodiques; Electromyography; Kinesiology; Electronic journals; Periodicals; 616.740757
• DOI: 10.1016/j.jelekin.2018.07.002
• Languages: English
• ISSNs: 1050-6411

Abstract

Abstract: Objective: To determine if maximal isometric contraction (MVIC) method (i.e., ramp (MVICRAMP ) versus traditional MVIC) influences (1) maximal voluntary isometric torque (MVIT) production of the knee extensors, (2) electromyographic signal amplitude (EMGAMP ), and (3) EMG mean power frequency (EMGMPF ) of the rectus femoris and vastus lateralis in moderately-to highly-activated subjects. We hypothesized that EMGAMP would be greater during the MVICRAMP than MVIC muscle contractions, but that there would be no difference in MVIT. Approach: Twenty-five males (23.4 ± 3.4 y; % voluntary activation = 93.9 ± 5.1%) visited the laboratory and completed MVICRAMP s and MVICs. During all contractions, leg extensor torque and sEMG signals from the vastus lateralis (VL) and rectus femoris (RF) were recorded. Main results: There was no significant difference in the MVIT produced ( p = 0.65) or in EMGMPF ( p = 0.052) during MVICRAMP versus MVIC. However, EMGAMP was 18.1% higher during the MVICRAMP than MVIC ( p = 0.004). Significance: Maximal isometric muscle contraction method significantly influenced EMGAMP, and had a moderate effect on EMGMPF ( d = 0.49). Investigators who utilize MVICs to determine maximal EMG signal amplitude and frequency to normalize their EMG signals should be aware of these differences.