Functional and morphological changes in the quadriceps muscle induced by eccentric training after ACL reconstruction

Abstract

Objectives: The purpose of this study was to investigate the contributions of functional and morphological factors in the recovery of the quadriceps muscle after anterior cruciate ligament (ACL) reconstruction. Methods: Nine subjects (31.3±5.8 years) underwent eccentric exercise sessions twice a week for 12 weeks. Quadriceps muscle function was evaluated using an isokinetic dynamometer (isometric and eccentric peak torque) and electromyography (RMS). Morphological changes were measured using magnetic resonance imaging. Results:The initial evaluation showed a significant deficit in knee extensor torque in the involved limb and significant muscle atrophy along the length of the quadriceps. EMG activity was lower in all tested situations. Eccentric training significantly increased isokinetic torque (from 199±51 to 240±63, p<0.05, respectively) and quadriceps area, with the greatest hypertrophy in the proximal thigh region (from 169±27 to 189±25.8 cm 2 , p<0.01). The EMG activity of vastus medialis increased after the first six weeks of eccentric training. The increased extensor torque was correlated with quadriceps cross-sectional area (r=0.81, p<0.01) and EMG activity (r=0.69, p<0.05).After twelve weeks of training, there was a correlation only between torque and cross-sectional area (r=0.78, p<0.01). Conclusions: 1) eccentric training proved to be a potent resource for the quadriceps recovery, both morphologically and functionally, 2) the contributions of functional and morphological factors varied according to the length of training.Key words: anterior cruciate ligament; electromyography; magnetic resonance; quadriceps muscle. ResumoObjetivos: O propósito deste estudo foi avaliar as contribuições dos fatores funcionais e morfológicos na recuperação da força muscular do quadríceps femoral após reconstrução do Ligamento Cruzado Anterior (LCA). Métodos: Nove indivíduos (31,3±5,8 anos) foram treinados por meio de contrações excêntricas máximas, duas vezes por semana, durante 12 semanas. A função do quadríceps foi avaliada pela dinamometria isocinética (pico de torque isométrico e excêntrico) e pela eletromiografia (EMG). As alterações morfológicas foram mensuradas por meio de ressonância magnética (RNM). Na avaliação inicial, observou-se significativo déficit no torque extensor do joelho do membro acometido, com hipotrofia muscular de todo o quadríceps e redução na atividade EMG, quando comparado ao membro não-acometido. Resultados: O treinamento excêntrico produziu aumento no torque excêntrico a 30º/s (de 199±51 Nm para 240±63 Nm, p<0,05) e no volume muscular, sendo que maiores hipertrofias ocorreram na região proximal da coxa (de 169±27 para 189±25,8 cm 2 , p<0,01). A atividade EMG do Vasto Medial (VM) aumentou nas primeiras seis semanas de treinamento. O aumento no torque extensor demonstrou correlação positiva com o aumento no volume (r=0,81, p<0,01) e na atividade eletromiográfica (EMG) (r=0,69, p<0,05) nas primeiras seis semanas. Após 12 semanas de treinamento, houve correlação apenas entre o aumento d...

Effect of Eccentric Strengthening After Anterior Cruciate Ligament Reconstruction on Quadriceps Strength

“…Four relevant studies [5][6][7][8] were located and categorized as shown in Table 1 (based on Levels of Evidence, Centre for Evidence-Based Medicine, 2011).…”

“…Characteristic Gerber et al 5 Gerber et al 6 Coury et al 7 Brasileiro et al 8 the majority of participants had gains in quadriceps strength reported at both time points (Table 2). Eccentric strengthening programs initiated approximately 9 months postreconstruction also seem to positively influence quadriceps strength.…”

“…7,8 • All 4 studies [5][6][7][8] supported the use of eccentric strengthening to improve quadriceps strength after ACL reconstruction.…”

“…These studies were selected because they had a level of evidence of grade 3 7,8 or higher, 5,6 studied an eccentric-exercise intervention, and reported the effect of the intervention on quadriceps strength in the ACL-reconstructed limb.…”

“…6 It should be noted, however, that results from the 1-yearpostsurgery study 6 are a follow-up on the same cohort of ACL-reconstructed subjects from the initial study. 5 Although additional subjects were recruited and added to the data reported from the 1-year-postoperative study, 6 Gerber et al 6 Coury et al 7 Brasileiro et al 8 Participants 32 ACL-reconstructed patients randomly assigned to concentric (TRAD; n = 16; 7 female, 9 male; age 31.0 ± 9.8 y) or eccentric exercise (ECC; n = 16; 7 female, 9 male, age 29.4 ± 9.4 y) intervention. Subjects matched by surgical procedure, sex, and age.…”