Heart rate variability and the exercise pressor reflex during dynamic handgrip exercise and postexercise arterial occlusion.
BACKGROUND
The exercise pressor reflex is thought to be an important cardiovascular control mechanism that may be compromised in disease states such as congestive heart failure and other metabolic syndromes. The purpose was to describe the exercise pressor reflex by observing heart rate variability and blood pressure responses to handgrip-exercise and postexercise arterial occlusion.


METHODS
Continuous electrocardiography, arterial blood pressure, and pneumotachogram data were collected on 38 participants (age, 20 +/- 1 year) during spontaneous breathing, venous-occluded exercise (60% maximal voluntary contraction, 0.5 Hz) and immediate postexercise arterial occlusion. Data were analyzed for mean R-R interval, standard deviation of R-R intervals (SDNN), normalized low (0-0.15 Hz) frequency power (LFnu), mean arterial pressure (MAP), and respiratory rate.


RESULTS
During exercise, increases in respiratory rate (+4.55 +/- 6.48 breaths/min), LFnu (+9.39 +/- 16.83%), and MAP (+25.40 +/- 17.55 mm Hg) were observed. Mean R-R interval (-230.73 +/- 125.79 msec) and SDNN (-38.54 +/- 36.02 msec) decreased (P < 0.05). Respiratory rate (+0.12 +/- 4.61 breaths/min), SDNN (-17.89 +/- 64.41 msec), and LFnu (9.89 +/- 21.01%) recovered during forearm arterial occlusion (P < 0.05). However, Mean R-R interval and MAP remained elevated above spontaneous breathing (P < 0.05).


CONCLUSIONS
The sustained elevation in MAP during postexercise arterial occlusion suggests metaboreceptor-mediated heightened sympathetic activity. The increase in LFnu during exercise and its subsequent recovery during postexercise occlusion is consistent with dynamic exercise-induced parasympathetic withdrawal but a strong vagal activation upon cessation of dynamic activity despite persistent sympathetic activity originating from afferent input from the occluded forearm.
Kluess
Heidi A
HA
Department of Kinesiology, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Wood
Robert H
RH
D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D018737:Hand Strength / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010275:Parasympathetic Nervous System / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012119:Respiration; D013564:Sympathetic Nervous System / Q000502:physiology*