Carotid baroreflex control of heart rate and blood pressure during ES leg cycling in paraplegics

Abstract

This study investigated control of heart rate (HR) and mean arterial pressure (MAP) at rest and during electrical stimulation (ES) leg cycling exercise (LCE) in paraplegics (Para). Seven men with complete spinal lesions (T(5)-T(11)) and six able-bodied (AB) men participated in this study. Beat-to-beat changes in HR and MAP were recorded during carotid sinus perturbation. Carotid baroreflex function curves were derived at rest and during ES-LCE for Para and during voluntary cycling (Vol) for AB. From rest to ES-LCE, oxygen uptake (VO(2)) increased (by 0.43 l/min) and HR rose (by 11 beats/min), yet MAP remained unchanged. In AB, Vol increased VO(2) (by 0.53 l/min), HR (by 22 beats/min), and MAP (by 8 mmHg). ES-LCE did not alter the carotid sinus pressure (CSP)-MAP relationship, but it displaced the CSP-HR relationship upward relative to rest. No rightward shift was observed during ES-LCE. Vol by AB produced an upward and rightward displacement of the CSP-MAP and CSP-HR relationships relative to rest. These findings suggested that the carotid sinus baroreflex was not reset during ES-LCE in Para.

Exercise Responses during Functional Electrical Stimulation Cycling in Individuals with Spinal Cord Injury

“…This is in comparison with the current study, where participants were either paraplegics with spinal lesions below T4 or possessed ''incomplete'' spinal lesions (ASIA B or C). Raymond et al (31) have proposed that FES-LCE lacks a ''central command'' component of leg exercise and also lacks complete skeletal muscle afferent feedback due to the spinal cord lesion. Thus, the underlying mechanisms for sympathetically induced exercise cardioacceleration driving such exercise would be blunted or lacking, resulting in the low peak HR observed herein.…”

External power output changes during prolonged cycling with electrical stimulation

“…There is little information concerning external power output (PO) production during ES-LCE, which is probably related to methodological aspects. Many studies (2,5,7,8) have used commercially available ES-LCE systems, in which cycling cadence is a system-controlled parameter. ES current output to the leg muscles is regulated by a microprocessor, which aims at maintaining a cycling rate of 50 revolution per minute (rpm).…”

Identifying the role of group III/IV muscle afferents in the carotid baroreflex control of mean arterial pressure and heart rate during exercise

“…multiple levels of NP and NS) and suggest no influence of these sensory neurons on baroreflex gain (Raymond et al . ; Gallagher et al . ; Smith et al .…”