Aim
Short periods of muscle disuse, due to illness or injury, result in substantial skeletal muscle atrophy. Recently, we have shown that a single session of neuromuscular electrical stimulation ...(NMES) increases muscle protein synthesis rates. The aim was to investigate the capacity for daily NMES to attenuate muscle atrophy during short‐term muscle disuse.
Methods
Twenty‐four healthy, young (23 ± 1 year) males participated in the present study. Volunteers were subjected to 5 days of one‐legged knee immobilization with (NMES; n = 12) or without (CON; n = 12) supervised NMES sessions (40‐min sessions, twice daily). Two days prior to and immediately after the immobilization period, CT scans and single‐leg one‐repetition maximum (1RM) strength tests were performed to assess quadriceps muscle cross‐sectional area (CSA) and leg muscle strength respectively. Furthermore, muscle biopsies were taken to assess muscle fibre CSA, satellite cell content and mRNA and protein expression of selected genes.
Results
In CON, immobilization reduced quadriceps CSA by 3.5 ± 0.5% (P < 0.0001) and muscle strength by 9 ± 2% (P < 0.05). In contrast, no significant muscle loss was detected following immobilization in NMES although strength declined by 7 ± 3% (P < 0.05). Muscle MAFbx and MuRF1 mRNA expression increased following immobilization in CON (P < 0.001 and P = 0.07 respectively), whereas levels either declined (P < 0.01) or did not change in NMES, respectively. Immobilization led to an increase in muscle myostatin mRNA expression in CON (P < 0.05), but remained unchanged in NMES.
Conclusion
During short‐term disuse, NMES represents an effective interventional strategy to prevent the loss of muscle mass, but it does not allow preservation of muscle strength. NMES during disuse may be of important clinical relevance in both health and disease.
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DOBA, FSPLJ, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Background:
Disuse leads to rapid skeletal muscle atrophy, which brings about numerous negative health consequences. Muscle disuse atrophy is, at least in part, attributed to a decline in basal ...(postabsorptive) muscle protein synthesis rates. However, it remains to be determined whether muscle disuse also impairs the muscle protein synthetic response to dietary protein ingestion.
Purpose:
We assessed muscle protein synthesis rates after protein ingestion before and after a period of disuse in humans.
Methods:
Twelve healthy young (24 ± 1 year) men underwent a 14-day period of one-legged knee immobilization by way of a full leg cast. Before and after the immobilization period, quadriceps cross-sectional area, muscle strength, skeletal muscle protein synthesis rates, and associated im (intramuscular) molecular signaling were assessed. Continuous infusions of l-ring-2H5phenylalanine were applied to assess mixed-muscle protein fractional synthetic rates after the ingestion of 20 g dietary protein.
Results:
Immobilization led to an 8.4% ± 2.8% (P < .001) and 22.9% ± 2.6% (P < .001) decrease in quadriceps muscle cross-sectional area and strength, respectively. Immobilization resulted in a 31% ± 12% reduction in postprandial muscle protein synthesis rates (from 0.046% ± 0.004% to 0.032% ± 0.006% per hour; P < .05). These findings were observed without any discernible changes in the skeletal muscle phosphorylation status of mammalian target of rapamycin or p70 ribosomal protein S6 kinase.
Conclusions:
A short period of muscle disuse impairs the muscle protein synthetic response to dietary protein intake in vivo in healthy young men. Thus, anabolic resistance to protein ingestion contributes significantly to the loss of muscle mass that is observed during disuse.
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