Title

Predictors of ambulatory post-exercise hypotension and heart rate recovery in adolescents with elevated and normal casual blood pressure using hierarchical linear modeling

Date of Award

2002

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Psychology

First Committee Member

Patrice G. Saab, Committee Chair

Abstract

The main purpose of this study was to describe blood pressure (BP) and heart rate (HR) recovery from maximal exercise using hierarchical linear modeling, and to document the phenomenon of post-exercise hypotension (PEH) in elevated and normotensive adolescents. Subjects were 75 elevated (n = 46) and normotensive (n = 29) boys and girls, ages 14--18. They performed a maximal treadmill exercise test during which maximal oxygen consumption, BP, and HR were measured. Shortly following exercise, subjects were fitted with ambulatory BP monitors. Systolic BP (SBP), diastolic BP (DBP), and HR were measured every 20 minutes following exercise for a 24-hour period. The duration and magnitude of post-exercise hypotension (PEH) were calculated for subjects in both BP groups, as well as for nine other cardiovascular disease (CVD) risk factors.During exercise, parallel increases in SBP and HR were observed for both BP groups, with the elevated adolescents having significantly higher levels of SBP, as compared to normotensives, at both baseline and maximal exercise. DBP remained unchanged from baseline levels for both BP groups. Elevated adolescents had a poorer aerobic fitness profile as indicated by their lesser VO2max, shorter exercise time, and lower METs at maximal exercise. These BP group differences, however, were not significant after controlling for BMI. Examination of Ratings of Perceived Exertion indicated that elevated adolescents perceived themselves as expending equal effort during maximal exercise as compared to normotensive adolescents.Across all subjects SBP PEH lasted for 0.45 hours (p < .05) with a maximum delta of 2.7 mm Hg below baseline (p < .05). DBP PEH did not occur significantly among a subset of 35 subjects whose DBP increased during exercise. At 1.43 hours post-exercise, HR was still 9.5 bpm above baseline HR levels (p < .05). There were no significant BP groups differences in post-exercise SBP or DBP recovery trajectories, nor were there BP group differences in SBP or DBP PEH duration and magnitude. The BP groups did have significantly different HR recovery trajectories, however, this did not translate to significant differences in HR recovery time towards baseline.Of the ten CVD risk factors, only Baseline SBP was positively associated with SBP PEH duration and magnitude. Three of the ten risk factors (Gender, Last Exercise DBP, and Baseline DBP) were positively associated with DBP PEH duration, however, after controlling for baseline DBP levels, only Gender differences remained significant. Race was the only CVD risk factor associated with HR time to recovery.These results document the occurrence of SBP PEH and elevated post-exercise HR, in adolescents, albeit for short durations, following a brief, yet intense period of exercise. The underwhelming association of PEH with CVD risk factors indicates that PEH does not appear to be a phenomenon associated with negative health. Furthermore, the small PEH durations and magnitudes found in this sample of adolescents implies that PEH has little clinical importance and is not a plausible explanation for the BP-lowering effects of chronic exercise. PEH may, however, be used as a tool to increase exercise adherence and motivation, but only in patients with high casual SBP. Future researchers should recognize the viability of hierarchical linear modeling and utilize its statistical advantages when describing and quantifying physiological recovery from challenge.

Keywords

Health Sciences, Recreation; Psychology, Physiological

Link to Full Text

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