Functional and biochemical properties of chronically stimulated human skeletal muscle

Abstract

The present study was undertaken to investigate in a randomized controlled trial the effects of chronic (10 weeks, 4 h per day, 7 days per week) low-frequency (15 Hz) stimulation (CLFS) of the knee extensor and hamstring muscles of both legs in healthy volunteers via surface electrodes. A control group (n=10) underwent the same treatment (sham stimulation) as the CLFS-treated group (n=10), except that stimulation intensity was kept at a level which did not evoke contractions. Biopsy samples were taken before the onset and after cessation of stimulation from the right vastus lateralis muscle of all subjects. The biopsy samples were analyzed for changes in myosin heavy chain (MHC) isoforms and activities of citrate synthase (CS) and glyceraldehyde phosphate dehydrogenase (GAPDH) as markers of aerobic-oxidative and anaerobic pathways of energy metabolism, respectively. In addition, functional properties, i.e., oxygen consumption (VO(2)) and work capacity, were assessed. Sham stimulation did not affect the functional properties and had no detectable effect on MHC isoform and enzyme activity patterns. Conversely, CLFS induced changes in the MHC isoform pattern in the fast-to-slow direction with an approximately 20% decrease in the relative concentration of MHCIId/x (from 28% to 22%) and an approximately 10% increase in the relative concentration of MHCI (from 30% to 34%). In addition, CLFS led to a approximately 9% increase in the activity of CS concomitant with an approximatley 7% decrease in the activity of GAPDH. This increase in aerobic-oxidative capacity was accompanied by improved work capacity and VO(2) at the anaerobic threshold by 26% and 20%, respectively.

Skeletal muscle effects of electrostimulation after COPD exacerbation: a pilot study

“…Consistent with the results obtained in healthy males [31], paraplegic males [32] and chronic heart failure patients [33] after an electrostimulation programme, we observed an increase in type I fibre proportion and a decrease in type IIx fibre proportion in COPD patients after exacerbation. These changes are usually interpreted as transition from fast-to-slow fibre type.…”

Nonpharmacological treatment and relief of symptoms in COPD: Table 1—

“…Within the framework of PR, transcutaneous neuromuscular electrical stimulation (NMES) of the lower limb muscles increases muscular oxidative capacities [28]. Small controlled studies with this technique in severe and even bed-bound COPD patients have been reported [29][30][31][32][33][34][35].…”

Lack of functional effects of neuromuscular electrical stimulation on skeletal muscle oxidative metabolism in healthy humans

“…Kim et al (21) reported, after a NMES training program, no changes in citrate synthase activity and number of capillaries. Nuhr et al (35) showed an increase in the activity of citrate synthase associated with a decrease in the activity of glyceraldehyde phosphate dehydrogenase. Interestingly, these molecular adaptations were not associated with clear effects in vivo.…”

“…Perez et al (36) observed an increase of the mean number of capillaries of fast-twitch (type II) fibers, but only minimal muscle hypertrophy, and no significant changes in aerobic performance. On the other hand, Nuhr et al (35) reported an improved work capacity and O 2 uptake (V O 2 ) at the anaerobic threshold following NMES. Compared with voluntary contractions of the same intensity, it has been reported that contractions obtained by NMES are associated with a greater (30,32) or similar (33) metabolic demand, and with an increased blood flow during recovery (32,45).…”