JOURNAL OF WOMEN’S HEALTH Volume 25, Number 9, 2016 ª Mary Ann Liebert, Inc. DOI: 10.1089/jwh.2015.5307

Cardiorespiratory Fitness, Body Fatness, and Submaximal Systolic Blood Pressure Among Young Adult Women Vivek Kumar Prasad, MD, MPH, PhD,1 Clemens Drenowatz, PhD,1 Gregory A. Hand, PhD,2 Carl J. Lavie, MD,3 Xuemei Sui, MD, MPH, PhD,1 Madison Demello, MS,1 and Steven N. Blair, PED1,4

Abstract

Objectives: We examined the independent and combined associations of cardiorespiratory fitness (CRF), body fat (BF) percentage (BF%), and body mass index (BMI) with submaximal systolic blood pressure (SSBP) among young adult women. Materials and Methods: Analyses included a sample of 211 normotensive women with a BMI between 20 and 35 kg/m2; BF% was calculated using total BF measured from dual X-ray absorptiometry, CRF was assessed using a graded exercise test, and SSBP was measured at each stage. Results: There was a significant direct association of SSBP with BF% and BMI, whereas an inverse association between SSBP and CRF when adjusted for the covariates. There was no significant association between SSBP and BF% across the stages 1–3 with a borderline significant association at stage 4 when further adjusted for CRF, whereas no association at any of the stages when adjusted for BMI. A borderline significant association between SSBP and BMI was found at stage 1 and significant association at stages 2–4 when additionally adjusted for CRF, whereas the association disappeared at stages 1–2 when adjusted for BF%. The inverse association between SSBP and CRF was eliminated at stages 3–4 when further adjusted for BF% with borderline significant association at stages 1–2. The associations remained significant at the stages 1–2 but not at stages 3–4 after adjusting for BMI. Conclusion: CRF, BF%, and BMI seem to have critical roles in determining SSBP with CRF and BF% being more potent at lower intensity exercise, whereas BMI was more strongly associated at higher intensity exercise.

Introduction

T

here has been a consistent corroboration by a number of studies that elevated exercise blood pressure (BP) is a marker of incidence of hypertension later in life among normotensive individuals.1,2 In addition, both rate and extent of elevation of submaximal systolic blood pressure (SSBP) during the graded exercise test (GXT) are predictors for myocardial infarction.3 It has been reported that individuals with elevated SSBP had a 2.3-fold increased risk of developing any strokes and 2.3-fold increased risk of developing ischemic stroke.4 A previous study reported that exaggerated SSBP among normotensive individuals is a predictor of left ventricular (LV) hypertrophy (LVH) by a probability of 0.64,5 which is associated with cardiac end organ damage.

SSBP at low levels of exercise intensity corresponding to usual daily activities may be an important marker of LVH among hypertensive individuals.6 Moreover, an exaggerated exercise BP response has a prognostic value for cardiovascular (CV) damage and mortality, which may be attributed to impaired left ventricular diastolic function, increased peripheral resistance, and LVH.7 Cardiorespiratory fitness (CRF) and aerobic exercise training exhibit protective roles on SSBP.8,9 Low CRF is associated with higher BP during submaximal exercise among hypertensive and normotensive women.9 An investigation analyzing the relationship between SSBP and body fat (BF) has reported that a decrease in BF is associated with lower SSBP among older adults.10 CRF and BF are associated with CV risk factors,11–14 morbidity, and mortality.15–18 Considering

1

Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina. School of Public Health, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia. 3 Ochner Clinical Sch-UQ School of Medicine, New Orleans, Louisiana. 4 Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina. 2

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the different levels of CRF and fatness in the population, it is critical to understand the independent and combined effect of CRF and fatness on CV and overall health.12,13,18–20 Some analysis suggests that CRF can negate the detrimental effect of obesity on health,20,21 whereas others report that higher categories of CRF attenuate but are unable to eliminate the adverse association of fatness with CV prognosis.19,22,23 To the best of our knowledge, there is no study that assesses the independent and combined effects of fitness and fatness (body fat percentage [BF%] and body mass index [BMI]) on SSBP, and it is important to understand whether CRF is associated with SSBP irrespective of fatness. Moreover, it is also important to determine if BF% is able to eliminate the association between SSBP and BMI. We, therefore, examined the independent and combined associations of CRF and fatness (BF% and BMI) with SSBP among young adult women. Materials and Methods

currently diagnosed with/or taking medications for a major chronic health condition, resting BP exceeding 140 mmHg systolic and/or 90 mmHg diastolic BP, a fasting blood glucose level of greater than 145 mg/dL, stopped or started smoking in the previous 6 months, use of medications to lose weight or planned weight loss surgery. Furthermore, women were excluded with a history of depression, anxiety, and panic, or taking selective serotonin inhibitors for any reason. Finally, women who became pregnant or had planned birth in the previous 12 months and those who had begun or changed their birth control regimen in the previous 3 months were also excluded. Anthropometry

BMI was calculated from the average of two height and weight measurements. Body composition was measured using a dual X-ray absorptiometry (DXA) scanner and used to calculate BF%.

Participants and enrollment process

Exercise testing procedure

The sample for this analysis included 211 normotensive (resting BP