Affiliations: [a] Laboratório de Fisiologia do Exercício e Biomecânica (LaFEB), Departamento de Educação Física e Esportes, Escola Naval, Marinha do Brazil, Brasil | [b] Programa de Engenharia Biomédica, COPPE, Universidade Federal do Rio de Janeiro, Brasil | [c] Laboratório de Biomecânica, Programa de Pós-Graduação em Educação Física, EEFD, Universidade Federal do Rio de Janeiro, Brasil
Correspondence:
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Corresponding author: Roger Gomes Tavares Mello, Biomedical Engineering Program - COPPE/UFRJ, P.O. Box 68510, 21941-972 - Rio de Janeiro, RJ, Brasil. Tel.: +55 21 3938 8632; Fax: +55 21 3938 8591; E-mail:rogerbiomec@gmail.com
Abstract: BACKGROUND: Muscle activity is studied during trunk stabilization
exercises using electromyograms (EMG) in time domain. However, the frequency
domain analysis provides information that would be important to understand
fatigue process. OBJECTIVE: To assess EMG of lumbar multifidus (LM) and erector
spinae (ES) muscles, in time and frequency domains, during back bridge
exercise. METHODS: Nineteen healthy young men performed the exercise for one
minute and EMG was monitored by surface electromyography. Normalized root
mean square (RMS) value and spectral median frequency (MF) were compared
between beginning and final epochs of test. The dynamics of the MF during
whole test was also obtained by short-time Fourier transform. RESULTS: RMS values were about 30% of maximum voluntary
contraction, and LM muscle showed greater MF than ES, which did not decrease
at the final of exercise. However, the slope of MF was significant mainly
for LM. CONCLUSIONS: Muscle activation of 30% is sufficient to keep
lumbar stability and is suitable to improve muscular endurance. The
significance of MF slope without decreasing at the final of exercise
indicates challenging muscular endurance without imply on high fatigability.
Due to lower muscular demand, this exercise might be recommended for trunk
stabilizing for low back pain patients.
Keywords: Back muscles, electromyography, exercise therapy, rehabilitation
