Musculoskeletal Plasticity After Acute Spinal Cord Injury: Effects of Long-Term Neuromuscular Electrical Stimulation Training

Abstract

Shields, Richard K., and Shauna Dudley-Javoroski. Musculoskeletal plasticity after acute spinal cord injury: effects of long-term neuromuscular electrical stimulation training. J Neurophysiol 95: 2380 -2390, 2006. First published January 11, 2006 doi:10.1152/jn.01181.2005. Maintaining the physiologic integrity of paralyzed limbs may be critical for those with spinal cord injury (SCI) to be viable candidates for a future cure. No long-term intervention has been tested to attempt to prevent the severe musculoskeletal deterioration that occurs after SCI. The purposes of this study were to determine whether a long-term neuromuscular electrical stimulation training program can preserve the physiological properties of the plantar flexor muscles (peak torque, fatigue index, torque-time integral, and contractile speed) as well as influence distal tibia trabecular bone mineral density (BMD). Subjects began unilateral plantar flexion electrical stimulation training within 6 wk after SCI while the untrained leg served as a control. Mean compliance for the 2-yr training program was 83%. Mean estimated compressive loads delivered to the tibia were ϳ1-1.5 times body weight. The training protocol yielded significant trained versus untrained limb differences for torque (ϩ24%), torque-time integral (ϩ27%), fatigue index (ϩ50%), torque rise time (ϩ45%), and between-twitch fusion (ϩ15%). These betweenlimb differences were even greater when measured at the end of a repetitive stimulation protocol (125 contractions). Peripheral quantitative computed tomography revealed 31% higher distal tibia trabecular BMD in trained limbs than in untrained limbs. The intervention used in this study was sufficient to limit many of the deleterious muscular and skeletal adaptations that normally occur after SCI. Importantly, this method of load delivery was feasible and may serve as the basis for an intervention to preserve the musculoskeletal properties of individuals with SCI.

An evaluation of the muscle-bone unit theory among individuals with chronic spinal cord injury

“…18 Consistent with our findings, when muscular activity of the plantar flexors was reintroduced in a study of seven people with motor complete SCI by an electrical simulation training program, there was an increase in trabecular BMD at the distal tibia. 19 In addition, a strong linear relationship has been reported between muscle CSA and BMC at the distal tibia site in children. 10 Although the associations were strongest between muscle and trabecular bone, we also found relationships between muscle and cortical bone.…”

Abdominal functional electrical stimulation to improve respiratory function after spinal cord injury: a systematic review and meta-analysis

“…As the thickness and hence strength of the abdominal muscles has been shown to be reduced in SCI, 38 one explanation for the chronic increases in FVC and PEF reported here is that even for patients with complete paralysis of the abdominal muscles, Abdominal FES training thickens and strengthens the abdominal muscles, altering the passive biomedical properties of the respiratory system. 10 Such strengthening of muscles after FES training has been demonstrated through a shift in the force frequency curve, 39 increased muscle blood supply 40 and muscle fibre type conversion towards more fatigue resistant fibres. 40,41 McLachlan et al 10 propose that this strengthening of the abdominal muscles leads to greater support of the abdominal contents, which act as a fulcrum as the diaphragm contracts, placing the diaphragm in a more efficient mechanical position to expand the lower lung after Abdominal FES training.…”

Human genome comparison of paretic and nonparetic vastus lateralis muscle in patients with hemiparetic stroke

“…In nondisabled volunteers, training can shift MHC to a slow profile with 60 percent MHC I, 30 percent MHC IIa, and 10 percent MHC IIx muscle fibers [29]. Similarly, functional electrical stimulation can shift the fast MHC isoform profile from SCI to a slow MHC profile [16,30]. Our laboratory is currently investigating whether an exercise intervention can reverse these MHC and MLC gene profiles in the paretic leg muscle after stroke.…”

“…Through insights from these genetic alterations in the paretic compared with the nonparetic leg muscles after stroke, we may develop therapeutic interventions that modify these altered gene expressions. Possible strategies could include pharmaceuticals [50][51], functional electrical stimulation [30,53], and aerobic or resistive exercise training. The beneficial effects of aerobic exercise training have been demonstrated in stroke [17,[54][55][56] and SCI rehabilitation programs [57][58][59][60].…”