Ashraf S Gorgey1, Justin Lawrence2. 1. Spinal Cord Injury and Disorders Center, Hunter Holmes McGuire VAMC, 1201 Broad Rock Boulevard, Richmond, VA 23249; and Department of Physical Medicine and Rehabilitation, Virginia Commonwealth University, Richmond, VA(∗). Electronic address: ashraf.gorgey@va.gov. 2. Spinal Cord Injury and Disorders Center, Hunter Holmes McGuire VAMC, and College of Health and Human Performance; Virginia Commonwealth University, Richmond, VA(†).
Abstract
BACKGROUND: Ventilation-to-carbon dioxide ratio is comparable with peak oxygen uptake in the prognosis of cardiovascular disorders. Currently, there are no established indices to determine the submaximal effects of functional electrical stimulation on cardiovascular performance in persons with spinal cord injury. OBJECTIVE: To determine the effects of an acute bout of functional electrical stimulation-lower extremity cycling on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization in people with motor complete spinal cord injury. DESIGN: Observational cross-sectional design. SETTING: Clinical laboratory setting. PARTICIPANTS: Ten individuals with motor complete spinal cord injury. METHODS: Participants were allowed to cycle until fatigue. The effects of functional electrical stimulation on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization were measured with a portable metabolic cart (COSMED K4b2). Body composition was determined with bioelectrical impedance. RESULTS: Resting and warm-up ventilation were 8.15 ± 3.5 L/min and 8.15 ± 2.8 L/min, respectively. Functional electrical stimulation increased ventilation significantly (14.5 ± 6.4 L/min), which remained significantly elevated (13.3 ± 4.3 L/min) during the recovery period. During resting and warm-up phases, the ventilation-to-carbon dioxide ratios were 41 ± 4.8 and 38 ± 5.4, respectively. Functional electrical stimulation decreased the ventilation-to-carbon dioxide ratio significantly to 31.5 ± 4, which remained significantly reduced during the recovery period (34.4 ± 3). Functional electrical stimulation relied primarily on carbohydrate utilization (188 ± 160 g/day to 574 ± 324 g/day; P = .001) with no changes in fat utilization (77.5 ± 28 g/day to 93.5 ± 133.6 g/day; P = .7) from resting to exercise periods. Significant relationships were noted between carbohydrate utilization during functional electrical stimulation and carbon dioxide (r = 0.98; P = .00010) production. The percentage whole body fat-free mass was negatively related to the exercise ventilation-to-carbon ratio (r = -0.66; P = .045). CONCLUSIONS: An acute bout of functional electrical stimulation resulted in a significant drop in the ventilation-to-carbon ratio, accompanied with a reliance on carbohydrate utilization and a diminished capacity to utilize fat as a substrate. Fat-free mass may be associated with a decrease in ventilation to carbon dioxide ratio and an increase in carbohydrate utilization in persons with spinal cord injury.
BACKGROUND: Ventilation-to-carbon dioxide ratio is comparable with peak oxygen uptake in the prognosis of cardiovascular disorders. Currently, there are no established indices to determine the submaximal effects of functional electrical stimulation on cardiovascular performance in persons with spinal cord injury. OBJECTIVE: To determine the effects of an acute bout of functional electrical stimulation-lower extremity cycling on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization in people with motor complete spinal cord injury. DESIGN: Observational cross-sectional design. SETTING: Clinical laboratory setting. PARTICIPANTS: Ten individuals with motor complete spinal cord injury. METHODS:Participants were allowed to cycle until fatigue. The effects of functional electrical stimulation on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization were measured with a portable metabolic cart (COSMED K4b2). Body composition was determined with bioelectrical impedance. RESULTS: Resting and warm-up ventilation were 8.15 ± 3.5 L/min and 8.15 ± 2.8 L/min, respectively. Functional electrical stimulation increased ventilation significantly (14.5 ± 6.4 L/min), which remained significantly elevated (13.3 ± 4.3 L/min) during the recovery period. During resting and warm-up phases, the ventilation-to-carbon dioxide ratios were 41 ± 4.8 and 38 ± 5.4, respectively. Functional electrical stimulation decreased the ventilation-to-carbon dioxide ratio significantly to 31.5 ± 4, which remained significantly reduced during the recovery period (34.4 ± 3). Functional electrical stimulation relied primarily on carbohydrate utilization (188 ± 160 g/day to 574 ± 324 g/day; P = .001) with no changes in fat utilization (77.5 ± 28 g/day to 93.5 ± 133.6 g/day; P = .7) from resting to exercise periods. Significant relationships were noted between carbohydrate utilization during functional electrical stimulation and carbon dioxide (r = 0.98; P = .00010) production. The percentage whole body fat-free mass was negatively related to the exercise ventilation-to-carbon ratio (r = -0.66; P = .045). CONCLUSIONS: An acute bout of functional electrical stimulation resulted in a significant drop in the ventilation-to-carbon ratio, accompanied with a reliance on carbohydrate utilization and a diminished capacity to utilize fat as a substrate. Fat-free mass may be associated with a decrease in ventilation to carbon dioxide ratio and an increase in carbohydrate utilization in persons with spinal cord injury.
Authors: Ashraf S Gorgey; Oksana Witt; Laura O'Brien; Christopher Cardozo; Qun Chen; Edward J Lesnefsky; Zachary A Graham Journal: Eur J Appl Physiol Date: 2018-12-11 Impact factor: 3.078
Authors: Ashraf S Gorgey; Zachary A Graham; William A Bauman; Christopher Cardozo; David R Gater Journal: J Spinal Cord Med Date: 2016-10-13 Impact factor: 1.985
Authors: Laura C O'Brien; Zachary A Graham; Qun Chen; Edward J Lesnefsky; Christopher Cardozo; Ashraf S Gorgey Journal: Spinal Cord Date: 2018-03-20 Impact factor: 2.772
Authors: Raymond E Lai; Matthew E Holman; Qun Chen; Jeannie Rivers; Edward J Lesnefsky; Ashraf S Gorgey Journal: PLoS One Date: 2022-03-11 Impact factor: 3.240