Effects of electrical stimulation and stretching on the adaptation of denervated skeletal muscle: implications for physical therapy.

BACKGROUND: This review will describe the main cellular mechanisms involved in the reduction and increase of myoproteins synthesis commonly associated with muscle atrophy and hypertrophy, respectively.
OBJECTIVE: We analyzed the effects of electrical stimulation (ES) and stretching exercise on the molecular pathways involved in muscle atrophy and hypertrophy. We also described the main effects and limits of these resources in the skeletal muscle, particularly on the denervated muscle. DISCUSSION: Recently, our studies showed that the ES applied in a similar manner as performed in clinical practice is able to attenuate the increase of genes expression involved in muscle atrophy. However, ES was not effective to prevent the loss of muscle mass caused by denervation. Regarding to stretching exercises, their mechanisms of action on the denervated muscle are not fully understood and studies on this area are scarce. Studies from our laboratory have found that stretching exercise increased the extracellular matrix remodeling and decreased genes expression related to atrophy in denervated muscle. Nevertheless, it was not enough to prevent muscle atrophy after denervation.
CONCLUSIONS: In spite of the use of stretching exercise and ES in clinical practice in order to minimize the atrophy of denervated muscle, there is still lack of scientific evidence to justify the effectiveness of these resources to prevent muscle atrophy in denervated muscle.