Análise de parâmetros de força e resistência dos músculos eretores da espinha lombar durante a realização de exercício isométrico em diferentes níveis de esforço

Abstract

The low-back pain has demonstrated to be a common finding among athletes and particularly the overload in the lumbar column resulting from a strength or isometric resistance involvement of muscles of this segment as result of the muscular fatigue has been considered as important etiological factor for its development. In this context, tests used for the training evaluation of the lumbar spinae erector muscles are emphasized. In the present study, the analysis of the strength and isometric resistance parameters was used with the objective of evaluating responses of these muscles during maximal and sub-maximal voluntary isometric contractions (MVIC) in two situations: with fatigue and without fatigue induced by isometric exercise performed until exhaustion. Nine male healthy volunteers performed MVIC before and after vertebral column extension exercises supporting 5%, 10%, 15% and 20% of the MVIC. In each one of these situations, the electromyographic signal (EMG) of the iliocostalis and multifidus muscles as well as the strength level generated in the MVIC were recorded. Muscular fatigue was identified through the MVIC values decrease verification and median frequency (MF) of the EMG signals obtained after isometric exercise. The results demonstrated that while the strength was able to evidence muscular fatigue, the MF demonstrated in a statistically significant way the iliocostalis and multifidus muscles fatigue, and the multifidus muscles presented a higher muscular fatigue level. Interestingly, loads between 5% and 20% of the MVIC induced the same level of muscular fatigue. Thus, although the strength generated during vertebral column extension after isometric exercise-induced exhaustion remains unchanged, probably due to the action of accessory muscles, the overload on the vertebral column is developed as result of the vertebral column stability involvement resulting from the muscular fatigue identified after isometric exercise.

Influence of subcutaneous fat on mechanomyographic signals at three levels of voluntary effort

“…The volunteers performed three maximal voluntary contractions (MVC) of 5 s with 5 min interval between them to avoid possible effects of fatigue (Correa et al, 2011;Gonçalves and Barbosa, 2005). Verbal encouragement was given in all trials (Baptista et al, 2009), and the highest value obtained was used as reference to define the submaximal values of 40% of MVC and 70% of MVC.…”

Comparação da fadiga eletromiográfica dos músculos paraespinhais e da cinemática angular da coluna entre indivíduos com e sem dor lombar

“…Quando há déficit no desempenho deste grupo muscular, ocorre a instabilidade da coluna (4)(5) . Isto resulta em frouxidão ligamentar, alteração no controle muscular, dor e predispõe a fadiga muscular (6)(7) . A fadiga muscular é definida como falha ou diminuição da força durante atividades de sustentação ou repetição (8) .…”

Método Isostretching como tratamento da dor lombar

“…A sobrecarga mecânica na coluna lombar leva a um comprometimento da força e resistência isométrica de músculos estabilizadores dessa região, resultando na fadiga muscular (GONÇALVES;BARBOSA, 2005). Porém, o principal fator causal da dor lombar é o desequilíbrio na força muscular, associada à redução da mobilidade da coluna e encurtamento da cadeia posterior (FREITAS;GREVE, 2008), decorrente de uma postura incorreta ou compensatória por um longo período.…”