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Acute Responses of Functional Electrical Stimulation Cycling on the Ventilation‐to‐CO 2 Production Ratio and Substrate Utilization After Spinal Cord Injury
Author(s) -
Gorgey Ashraf S.,
Lawrence Justin
Publication year - 2016
Publication title -
pmandr
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.617
H-Index - 66
eISSN - 1934-1563
pISSN - 1934-1482
DOI - 10.1016/j.pmrj.2015.10.006
Subject(s) - functional electrical stimulation , ventilation (architecture) , medicine , spinal cord injury , carbon dioxide , anesthesia , stimulation , respiratory exchange ratio , respiratory minute volume , respiratory system , spinal cord , heart rate , chemistry , mechanical engineering , organic chemistry , psychiatry , blood pressure , engineering
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.