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Clinical Trial
. 2020 Sep;8(18):e14581.
doi: 10.14814/phy2.14581.

Short-term water deprivation attenuates the exercise pressor reflex in older female adults

Affiliations
Clinical Trial

Short-term water deprivation attenuates the exercise pressor reflex in older female adults

Joseph C Watso et al. Physiol Rep. 2020 Sep.

Abstract

Older adults have reduced fluid intake and impaired body fluid and electrolyte regulation. Older female adults exhibit exaggerated exercise blood pressure (BP) responses, which is associated with an increased risk of adverse cardiovascular events. However, it is unclear if dysregulated body fluid homeostasis contributes to altered exercise BP responses in older female adults. We tested the hypothesis that short-term water deprivation (WD) increases exercise BP responses in older female adults. Fifteen female adults (eight young [25 ± 6 years] and seven older [65 ± 6 years]) completed two experimental conditions in random crossover fashion; a euhydration control condition and a stepwise reduction in water intake over three days concluding with a 16-hr WD period. During both trials, beat-to-beat BP (photoplethysmography) and heart rate (electrocardiogram) were continuously assessed during rest, handgrip exercise (30% MVC), and post-exercise ischemia (metaboreflex isolation). At screening, older compared to young female adults had greater systolic and diastolic BP (p ≤ .02). Accelerometer-assessed habitual physical activity was not different between groups (p = .65). Following WD, 24-hr urine flow rate decreased, whereas thirst, urine specific gravity, and plasma osmolality increased (condition: p < .05 for all), but these WD-induced changes were not different between age groups (interaction: p ≥ .31 for all). Resting systolic and diastolic BP values were higher in older compared to young adults (p < .01 for both), but were not different between experimental conditions (p ≥ .20). In contrast to our hypothesis, WD was associated with attenuated systolic BP responses during handgrip exercise (post hoc: p < .01) and post-exercise ischemia (post hoc: p = .03) in older, but not young, female adults. These data suggest that reduced water intake-induced challenges to body fluid homeostasis do not contribute to exaggerated exercise BP responses in post-menopausal female adults.

Keywords: aging; exercise pressor reflex; hypohydration.

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Conflict of interest statement

The authors report no competing interests regarding the current article.

Figures

FIGURE 1
FIGURE 1
In random crossover fashion, 15 female participants completed both a euhydrated control (CON) protocol and a water deprivation (WD) protocol prior to laboratory testing on day four. In the laboratory, we assessed beat‐to‐beat blood pressure and heart rate during a handgrip exercise trial and cold pressor test
FIGURE 2
FIGURE 2
Handgrip exercise. Summary data with individual data points are presented for cardiovascular responses during the final minute of handgrip exercise (HG). Open bars indicate the euhydrated control condition (CON) and closed bars indicate the water deprived condition (WD).Systolic and mean blood pressure (BP) responses were lower during the WD in older adults and were not different between conditions in young adults. Diastolic BP responses were lower in old compared to young adults during WD. Systemic vascular resistance and heart rate responses during HG were not different between age groups or conditions. Young compared to older adults had augmented cardiac output responses. * indicates significant main effect of age
FIGURE 3
FIGURE 3
Post‐exercise ischemia. Summary data with individual data points are presented for cardiovascular responses during the final minute of post‐exercise ischemia (PEI). Open bars indicate the euhydrated control condition (CON) and closed bars indicate the water deprived condition (WD). Systolic blood pressure (BP) was greater in older compared to young adults during CON. Systolic, mean, and diastolic BP responses were lower in WD in older adults, and not different between conditions in young adults. Systemic vascular resistance, heart rate, and cardiac output responses were not different between age groups or conditions
FIGURE 4
FIGURE 4
Age‐related differences in systolic blood pressure (BP) responses to handgrip exercise and post‐exercise ischemia after water deprivation (WD). Summary data (gray bars) with individual data points are presented for systolic BP responses (WD minus CON [euhydrated control condition]) during the final minute of handgrip exercise (left) and post‐exercise ischemia (right). These data indicate that the condition‐related differences in systolic BP responses were different between age groups. Specifically, the positive group mean for the young group suggests greater BP responses during WD whereas the negative group mean for the older group suggests greater BP responses during CON
FIGURE 5
FIGURE 5
Cold pressor test. Summary data with individual data points are presented for cardiovascular responses during the final minute of the cold pressor test (CPT). Open bars indicate the euhydrated control condition (CON) and closed bars indicate the water deprived condition (WD). Systolic, mean, and diastolic blood pressure (BP) responses during the CPT were not different between age groups or conditions. Systemic vascular resistance, heart rate, and cardiac output responses were also not different between age groups or conditions

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