Abstract
The purpose of this study was to evaluate the effects of electric stimulation as a countermeasure to prevent disuse atrophy of skeletal muscles by assessing energy metabolism in the working muscle by 31P-MRS. Sprague-Dawley rats were used and divided into three groups: control group (C), hindlimb suspended for 7 days (HS), and HS plus percutaneous electric stimulation for 7 days (ES). Electric stimulation for training of the gastrocnemius-plantaris-soleus (GPS) muscles was attained at 1Hz for 1 hour everyday. For 31P-MRS measurements, contraction of the GPS muscles was induced by electrical stimulation of the sciatic nerve at 0.25Hz for 10min following a 2-min rest, then the frequency was increased to 0.5 and 1.0Hz every 10min. During the stimulation, twitch forces were recorded by a strain gauge simultaneously. The energy metabolism in the working muscles was analyzed from the 31P-MR spectra. Maximum tension was measured at the muscle contraction induced by 0.25Hz; the wet weight of the whole GPS muscles was also measured. The weight of the whole GPS muscles decreased significantly (p<0.05) in HS and ES groups. The maximum twitch tension in HS was significantly smaller than that in C (p<0.05) while in ES it did not differ from that in C. The oxidative capacity of muscles decreased within one week in HS; however, it was maintained for one week when electric stimulation was applied to the suspended limb. These data indicated that twitch electric stimulation did not prevent atrophy, but prevented deterioration in the muscle functions, such as maximum tension and oxidative capacity. induced by disuse during one week.
