Neural changes in the spinal cord rights for different types of physical training / Adaptações neurais na medula espinhal de humanos para diferentes tipos de treinamento físico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Introduction: Neural adaptations with physical training have been widely studied. The spinal cord is a possible locus of adaptation. However, longitudinal studies that evaluate directly the spinal cord pathways have not been found in the literature. Therefore, all reports from the literature justify changes found in measured responses to exercise by hypotheses on spinal cord mechanisms. This study had the objective of measuring features of specific spinal cord pathways to check if they change according to the type of physical training. The pathways related to reciprocal inhibition (RI) and pre-synaptic inhibition (PSI) were investigated in subjects undergoing different trainings. Materials and Methods: For endurance training 25 soldiers were subjected to military training of the Brazilian Army. Evaluations were made three times, one previous to the beginning of the activity and twice post-training (within 3 and 9 months). Other 29 subjects were divided into: control group (with no training), maximal strength group and power group. They were subjected to 8 weeks of training with series of squat movements. The soleus H reflex conditioning with stimuli in the common peroneal nerve (CPN) was used to evaluate the spinal cord pathways. The interval between the conditioning and the test stimulus determine the assessment of RI, D1 inhibition and D2 inhibition (PSI). Other variables were also calculated: maximum voluntary isometric contraction from soleus and tibialis anterior and their electromyograms (EMG), electrical and mechanical Hmax/Mmax ratio and 3 inhibitions over the soleus EMG conditioned by stimuli to the CPN. The results were analyzed with paired t-student test for the military group and with two-way ANOVA to compare the maximal strength and power groups with the control group. Main Results: The military group had increased strength of the soleus and the TA muscles, with an increase in the RMS of the soleus EMG. This group also increased the torque generated by the Mmax-wave, without changes in Hmax/Mmax ratio. The military training significantly reduced D1 inhibition and showed tendencies to increase the PSI. The maximal strength group showed no differences in isometric strength, but had increased Hmax/Mmax ratio with concomitant reduction of RI and increased PSI. The power group increased isometric strength only for the soleus muscle. This group also improved the ability to generate torque by reflex pathways, with significant increase in the mechanical Hmax/Mmax ratio, with a reduction of PSI and increase of RI. Conclusions: These results show that spinal cord plasticity occurs in the inhibitory pathways of reciprocal inhibition, D1 inhibition and D2 inhibition (pre-synaptic inhibition), and that plasticity is dependent on the type of trained movement.

ASSUNTO(S)

neuronal plasticity physisical activity reciprocal inhibition inibição pré-sináptica medula espinhal inibição recíproca atividade física plasticidade neuronal spinal cord h reflex presynaptic inhibition reflexo h

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