Alterações funcionais e morfológicas do músculo quadríceps induzidas pelo treinamento excêntrico após reconstrução do LCA.
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Data
2004-12-10Autor
Brasileiro, Jamilsom Simões
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The anterior cruciate ligament (ACL) is the most commonly injured ligament in the knee and its
rupture results in pain, instability, muscle atrophy and weakness. The quadriceps femoris muscle
dysfunction is common before and after ACL reconstruction and can persist over years. A
detailed understanding of neuromuscular function after ACL reconstruction is critical to the
development of optimal rehabilitation strategies. The purpose of this study was to investigate the
contributions of functional and morphological factors, in the muscle recovery, after ACL
reconstruction. The effects of two therapeutic methods, usually utilized to recover muscle
strength were also evaluated: Neuromuscular Electrical Stimulation (NMES) and eccentric
exercise. Eight subjects (age = 31.3 ± 5.8 years) who had undergone ACL ligament
reconstruction (mean 9.4 ± 0.7 months after the surgery) were randomly assigned to either an
eccentric exercise associated with NMES (russian current) or only an eccentric exercise group.
Only the involved limb was trained 2 days a week, for 12 weeks. The uninvolved one was also
evaluated as reference. The quadriceps muscle function was evaluated by the measurement of the
knee extensor torque during isometric and eccentric isokinetic contractions (30 and 120º/s) and
by surface electromyography (EMG) of the Vastus Medialis Obliquos (VMO), Vastus Lateralis
(VL) and Rectus Femoris (RF) muscles. The quadriceps cross-sectional area (CSA) was
measured in six regions using Nuclear Magnetic Resonance Imaging (MRI-I). The initial
evaluation showed significant extensor torque deficit both in isometric and eccentric conditions
of the involved limb, compared to the contralateral one. There was significant muscle atrophy
along the quadriceps extension, mainly in the distal thigh region. The EMG activity was lower for
the VMO in all tested situations. NMES did not interfere in the gain of muscular strength, in any
of the evaluated functions. The eccentric training increased significantly the isometric (from 198
± 37 to 228 ± 48 Nm, p<0.05) and eccentric torque at 30 and 120º/s (from 227 ± 56 to 291 ± 65,
p< 0.01 and from 199 ± 51 to 240 ± 63, p< 0.05, respectively). Quadriceps cross-sectional area
also increased at all the evaluated regions for the involved limb, and the highest hypertrophy was
at the thigh proximal region (from 169 ± 27 to 189 ± 25,8 cm2, p< 0.01 ), when compared to the
distal region (form 31,5 ± 5,9 to 35,1 ± 6,1 cm2, p< 0.01). The EMG activity of VMO was
recovered after the first six weeks of eccentric training. In the same period, the increased extensor
torque showed correlation with the increased quadriceps cross-sectional area (r=0,81) and with
the recovery of motor unit activation (r=0.69). After twelve weeks of training, there was
correlation only between increased torque and cross-sectional area (r=0.78). In conclusion: 1)
eccentric training showed to be a potent resource in the recovery of both morphological and
functional factors of quadriceps, after ACL reconstruction; 2) NEMS did not interfere in the
rehabilitation of these individuals.