Treadmill training–induced adaptations in muscle phenotype in persons with incomplete spinal cord injury

Abstract

Body weight-supported treadmill (BWST) training has been shown to improve ambulatory capacity in persons with a spinal cord injury (SCI); however, the effect that BWST training has on skeletal muscle phenotype is unknown. We aimed to determine whether 6 months (three sessions/week) of BWST training in neurologically stable persons with a traumatic spinal cord injury (ASIA C) alters skeletal muscle phenotype, ambulatory capacity, and blood lipid profile. Externally supported body weight decreased, and walking velocity and duration of the training sessions increased (all P Ͻ 0.05) as a result of training. Muscle biopsies revealed increases in the mean muscle-fiber area of type I and IIa fibers. Training induced a reduction in type IIax/IIx fibers, as well as a decrease in IIX myosin heavy chain, and an increase in type IIa fibers. Maximal citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase activity also increased following training. BWST training brought about reductions in plasma total (Ϫ11%) and low-density lipoprotein (Ϫ13%) cholesterol. We conclude that, in patients with a spinal cord injury, BWST training is able to induce an increase in muscle fiber size and bring about increases in muscle oxidative capacity. In addition, BWST training can bring about improvements in ambulatory capacity and antiatherogenic changes in blood lipid profile. Trauma to the spinal cord can cause motor and sensory dysfunction of varying degrees distal to the level of the lesion. The distal limb musculature below the level of trauma undergoes a pronounced atrophy 1,5,22,27 and a general "deconditioning" including a reduction in oxidative potential, 7,22 and a shift toward the fast, and specifically type IIx, fiber population. 1,7,14,23,28 These changes undoubtedly lead to a higher muscle fatigability. 12,15 Therapies aimed at improving the injury-induced deconditioning of skeletal muscle in persons with a spinal cord injury (SCI) are highly relevant due to the low quantity (due to atrophy) and oxidative capacity of the paralyzed skeletal muscle. 7,22 A number of studies have shown that, in persons with a complete SCI, functional electrical stimulation (FES) training is able to reverse the SCI-induced atrophy, increase muscle oxidative potential, and improve fatigue resistance. 7,12,15,18,23 Persons with an incomplete SCI frequently identify independent ambulation as one of their primary rehabilitation goals. 2,10 Although FES promotes important phenotypic changes in persons with SCI,7,12,15,18,23 there is no evidence that FES improves ambulatory capacity in persons with incomplete SCI. Body weight-sup-

Electrical Stimulation During Gait Promotes Increase of Muscle Cross-sectional Area in Quadriplegics: A Preliminary Study

“…The effect of gait on muscle CSA in spinal cord-injured patients was reported by few studies, which contrasts our results [14,24]. In one study, there was an increase of 4.9% in thigh muscle area and 8.2% in the lower leg after 12 months of gait training (three times a week, totaling 144 sessions) without NMES; however, this study included only incomplete spinal cord injuries, paraplegia and quadriplegia [14].…”

“…A reversal of muscle atrophy in acute patients with incomplete quadriplegia (American Spinal Cord Injury Association B and C) after 48 sessions of treadmill gait training twice a week also was reported [13]. Stewart et al [24] reported an increase in size of Types I and IIa fibers with restoration of the normal size of muscle fibers after 6 months of gait (68 sessions) without NMES beginning with 65% ± 3% and ending with 23% ± 5% of BWS in individuals with incomplete (American Spinal Cord Injury Association C) paraplegia and quadriplegia. NMES = neuromuscular electrical stimulation.…”

The effects of exercise training on physical capacity, strength, body composition and functional performance among adults with spinal cord injury: a systematic review

“…All were classified as level 4 or 5, with the exception of one level 2 trial. Training programs involving BWSTT, 32,34,35 FES cycling, 30,31,[36][37][38] FES ambulation, 39,40 neuromuscular electrical stimulation resistance training 41 and vibration exercise 42 produced significant increases in muscle mass, with training frequencies ranging from 2-7 Â per week, for 8-52 weeks duration. Of note, the level 2 trial showed significant increases in quadriceps muscle mass after 26 weeks of FES-assisted treadmill training, 2 times per week for 20 min per session.…”

Effect of Exercise on Disorders of Carbohydrate and Lipid Metabolism in Adults With Traumatic Spinal Cord Injury: Systematic Review of the Evidence

“…Only 3 subjects were assigned to each group, and no control group was included for comparison. There were 12 studies that reported carbohydrate-related outcomes (9,10,(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) (Table 1) and 15 that reported lipid-related outcomes (9,10,26,27,30,(35)(36)(37)(38)(39)(40)(41)(42)(43)(44) (Table 2). Only 1 study included cardiovascular morbidity as an endpoint (Table 2), and this was assessed using a survey instrument with variable levels of sensitivity and specificity when tested in able-bodied populations (45).…”