Effect of posture on heart rate control prior to and following dynamic leg exercise (881.8)

Abstract

Reflex control of cardiovascular function is paramount in maintaining homeostasis both before and after exercise. We investigated the influence of posture on arterial baroreflex function both before and after prolonged moderate to high intensity exercise. 9 healthy subjects (1 female) aged 24.4 years (±1.16) volunteered for protocol 1 of the study and 13 healthy subjects (3 female) aged 25.5 years (±0.88) volunteered for protocol 2. Each subject underwent graded exercise test either upright (UR) (protocol 1) or semi‐recumbent (SR) (protocol 2). During both protocols 1 and 2 neck pressure/neck suction protocols were performed at rest, exercising HRs of 120 and 150 bpm, and recovery. Reflex data for HR and MAP were analyzed and baroreflex curves were calculated. Repeated measure ANOVAs was performed and Neuman‐Keuls post hoc analysis was used when differences were detected. Significance was set at P<0.05. Significant differences were identified in operating point values of HR between SR and UR at rest (P<0.001), and between rest and recovery in both SR and UR (p<0.001). Differences were also identified in Carotid‐cardiac baroreflex response range and maximum gain between and within all conditions (p<0.05). Differences in the neural reflexive control of HR at rest and during recovery are related to postural changes in cardiopulmonary loading. Grant Funding Source: Supported by TACSM SRDA