A spinal cord injury (SCI) is a trauma-induced lesion to the spinal cord that totally or partially disconnects the central nervous system (CNS) from the muscles. This obliterates or reduces the ability to activate muscles below the level of the lesion, which can reduce muscle force production and thus impair physical function and profoundly compromise physical health and quality of life (QOL). Another important consequence of SCI is the development of spasticity, which represents one of the major complications that can affect functional ability and therefore QOL. Muscle strength training interventions such as resistance training can increase muscle force production and ameliorate symptoms of spasticity, and therefore improve physical health, function and QOL in people with SCI. Since neurally driven (i.e. voluntary) resistance training is limited in people with SCI, there is a requirement for muscle activation assistance. Neuromuscular electrical stimulation (NMES) is commonly used for this purpose, however a major problem associated with NMES is the rapid onset of muscle fatigue, which is largely caused by the simultaneous activation of the same motor units in repeated contractions, the random recruitment pattern (as opposed to the orderly recruitment from type I to Type II motor units in voluntary contractions), the unphysiologically high stimulation rates (e.g. > 20 Hz), and consequent muscle damage. With respect to overcoming these issues in the clinical setting, the use of wide pulse-width NMES (1000 μs) superimposed on tendon vibration seems a promising tool for eliciting greater peak muscle forces at lower stimulation intensities, thus inducing less fatigue.
The first purpose of the present research is to develop a new model of externally stimulated muscle strength training, possibly including ramped-frequency, wide pulse width (1000 μs) NMES superimposed on tendon vibration, which could elicit greater peak muscle force with less fatigue and thus allow for a greater total impulse (force × time) to be produced when compared to non-ramped frequency NMES without tendon vibration in people with and without SCI (Studies 1 and 2).
Subsequently, the second purpose of the research is to examine the effects of a 12-week externally stimulated (i.e. involuntary) muscle strength training program using a wide pulse-width NMES (1000 μs) protocol (developed in Studies 1 and 2) on muscle force production, symptoms of spasticity, functional capacity, physical health (i.e. muscle cross-sectional area, bone mineral density, systemic inflammation and lipid profile) and QOL when added to an existing activity-based exercise/rehabilitation program in people with SCI (Study 3).
This research will contribute to a better understanding of how different NMES resistance training interventions might elicit positive adaptive changes (i.e. muscle strength, hypertrophy) and thus improve physical function and health and QOL in people with SCI.
Spinal Cord Injuries Australia (SCIA).
Please leave a comment about your rating so we can better understand how we might improve the page.