1. Introduction
skeletal muscle, cord injury, metabolic disorders
CHRONIC METABOLIC DISORDER, TYPE 2 DIABETES, IMPAIRED GLUCOSE TOLERANCE, METABOLIC DISORDERS
Maintaining healthy myofiber type and metabolic function early after spinal cord injury (SCI) may prevent chronic metabolic disorders. This study compares the effects of a 2–5 week combined (aerobic + resistance) neuromuscular electrical stimulation (Comb-NMES) regimen versus a sham control treatment on muscle protein signaling for glucose uptake, myofiber type distribution, and metabolic function. Twenty participants (31 ± 9 years of age) with an SCI (C4-L1, AIS level A–C) within 14 days of the SCI were randomly assigned to control (The prevalence of metabolic disorders (e.g., type 2 diabetes, impaired glucose tolerance, and abnormal lipid profiles) is higher in those with spinal cord injury (SCI) vs. age- and sex-matched non-injured individuals [In healthy humans, up to 70% of whole-body glucose metabolism occurs in skeletal muscle. The regulation of glucose homeostasis is dependent on a finely balanced relationship between (i) muscle sensitivity to insulin and (ii) insulin secretion [These observations support the idea that rather than attempting to reverse changes in the sub-acute or chronic stage of SCI, early interventions are likely to more effective in the prevention of deleterious muscle adaptations. One potential and promising strategy to improve skeletal muscle metabolism is neuromuscular electrical stimulation (NMES). NMES-resistance training has been shown to increase the size and distribution (type IIa) of myofibers [To identify effective strategies for improving metabolic profiles among individuals with SCI, we aimed to test the impact of an early intervention (14 days after SCI) of a combined (aerobic + resistance) NMES (Comb-NMES) intervention on muscle growth and type distribution, signaling processes involved in muscle glucose uptake, and systemic metabolic responses. We tested the following hypotheses: (1) Comb-NMES will effectively upregulate signaling proteins that promote GLUT-4 translocation; and (2) Comb-NMES will maintain greater muscle size and a healthy muscle fiber phenotype (similar distribution of type I, IIa, and IIx fibers); and (3) Comb-NMES will produce beneficial changes in serum glucose, insulin, and lipid levels.