Acute hemodynamic responses of spinal cord injured individuals to functional neuromuscular stimulation-induced knee extension exercise

Abstract

Abstract-The purpose of this study was to determine and compare acute hemodynamic responses of spinal cord injured (SCI) quadriplegics (quads), and paraplegics (paras) during a gradedintensity knee extension (KE) exercise test utilizing functional neuromuscular stimulation (FNS) of paralyzed quadriceps muscles. Seven quads and seven paras (N=14) performed a series of 4-minute stages of bilateral alternating FNS-KE exercise (approximately zero to 70 degree range of motion at the knee and 6 KEIminlleg) at ankle loads of 0, 5, 10, and 15 kglleg. Physiologic responses were determined with open-circuit spirornetry, impedance cardiography, and auscultation. Comparing rest with peak FNS-KE for both groups combined, FNS-KE exercise elicited significant (p< 0.05) increases in oxygen uptake (130 percent), pulmonary ventilation (120 percent), respiratory exchange ratio (37 percent), arteriovenous oxygen difference (57 percent), cardiac output (32 percent), stroke volume (41 percent), mean arterial pressure (18 percent), and rate-pressure product (23 percent). Heart rate increased significantly by 11 percent from the 5-to the 15-kglleg stages. Physiologic responses of quads and paras were very similar, except for lower (p < 0.05) arterial pressures, rate-pressure product, and peripheral vascular resistance in quads. This graded FNS-KE exercise up to the 15-kglleg load induced relatively small but appropriate increases in aerobic metabolism and cardiopulmonary responses that appear to be safe and easily tolerated by quads and paras. Arterial pressure needs to be monitored carefully in quads to prevent excessive hypertension or hypotension. Although FNS-KE exercise has been shown to elicit peripheral adaptations to improve muscle strength and endurance, it is probably not an effective central cardiovascular training tool for all but the least fit SCI individuals. This information is important for understanding the effects of FNS use during more complex activities such as cycling and ambulation.

Cardiovascular responses to an orthostatic challenge and electrical-stimulation-induced leg muscle contractions in individuals with paraplegia

“…ES-induced muscle contractions have been suggested to assist in the redistribution of blood from the paralysed lower limbs (Glaser 1994). This has been demonstrated indirectly by studies that have documented an increase in SV (Glaser et al 1987;Figoni et al 1991) or left-ventricular diastolic ®lling (Davis et al 1993), during ES-induced leg muscle contractions. Therefore, the secondary purpose of this study was to determine if ES-induced leg muscle contractions in paraplegic subjects were eective for reversing venous pooling during the performance of an orthostatic challenge.…”

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training

“…Adaptations occur months or years after the lesion, allowing a change in body position without hypotension (12). The adaptation process probably involves the action of the renin-angiotensin system, antidiuretic hormone, aldosterone and arginine vasopressin, which are crucial in the regulation of blood pressure (13,14).…”

Enhancement of whole body glucose uptake during and after human skeletal muscle low-frequency electrical stimulation

“…The use of ES has been traditionally employed for muscle strengthening, maintenance of muscle mass and strength, and restoring neuromuscular functions after stroke or spinal cord injury (28). ES can also cause cardiorespiratory activation (4,7,20,44). Furthermore, there is substantial evidence concerning the effects of ES on metabolic responses and fuel utilization in skeletal muscle (12,19,26,27,44).…”