Dynamic exercise progressively decreased reflex tachycardia to neck pressure (P<0.05) but did not significantly alter the time to peak change in heart rate compared to rest (P>0.05).
p-value: p=>0.05
We compared the beat-to-beat responses of heart rate (HR) after brief activation of carotid baroreceptors in resting humans with the responses obtained during mild-to-moderate levels of dynamic exercise 25 and 50% of peak O2 uptake (VO2peak) to investigate the effect of exercise on baroreflex latency. Carotid baroreceptors were activated by a pressure pulse (5 s) of neck suction (NS, -80 Torr) and neck pressure (NP, +40 Torr) during held expiration. At rest the peak change in HR to NS/NP occurred during the first several heartbeats (1st-3rd beat), whereas during mild and moderate exercise peak HR responses occurred near the end of the NS/NP pulse (6th-8th beat). In contrast, time (s) to the peak change in HR was not different between rest and exercise (P > 0.05). Reflex tachycadia to NP progressively decreased during exercise (17 +/- 3, 10 +/- 1, and 4 +/- 1% of control, rest vs. 25% VO2peak, vs. 50% VO2peak, respectively, P < 0.05), and a strong positive correlation was found between the magnitude of the reflex tachycardia and a measure of HR variability (cardiac vagal tone index, r = 0.74, P < 0.0001). Reflex bradycardia to NS gradually increased during exercise (13 +/- 2, 17 +/- 2, and 18 +/- 2% of control, rest vs. 25% VO2peak, vs. 50% VO2peak, respectively, P = 0.10) and was negatively correlated with cardiac vagal tone (r = 0.42, P < 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)
Potts et al. (Wed,) reported a other. Dynamic exercise vs. Rest was evaluated on Time (s) to the peak change in heart rate (p=>0.05). Dynamic exercise progressively decreased reflex tachycardia to neck pressure (P<0.05) but did not significantly alter the time to peak change in heart rate compared to rest (P>0.05).