Raymond Blakely

Aerobic Exercise Attenuates an Exaggerated Exercise Blood Pressure Response in Normotensive Young Adult African-American Men

An exaggerated exercise blood pressure response (EEBPR) may be associated with an increased risk of hypertension. We hypothesized that aerobic exercise training can decrease EEBPR and the risk for hypertension by decreasing arterial resistance. We studied the effects of aerobic training on the submaximal exercise blood pressure (BP) of eight normotensive young adult African-American men with an EEBPR. Subjects were trained on a stationary bicycle at an intensity of 70% peak oxygen uptake (VO 2peak ), for 30 min, three times per week, for 8 weeks. BP, heart rate, cardiac output (CO), stroke volume (SV) and total peripheral vascular resistance (TPR) were measured at rest and during submaximal exercise at a work intensity of 50% VO 2peak. Significance of the training effects were evaluated by comparing the pre- and post-training measures ( t -test, p < 0.05). A 15% post-training increase in VO 2peak (34.6 - 1.4 to 40 - 1.4 ml/kg/min) and a 9.5 ml post-training increase in mean resting stroke volume were found. A 16.2 mmHg decrement in mean systolic BP, an 11.5 mmHg decrement in mean diastolic BP, a 120 dyne/s/cm 5 decrement in TPR and a 1.2 l/min increase in CO were detected during the posttraining submaximal exercise tests. These results suggest that reductions in TPR may attenuate the EEBPR of normotensive African-American males following an 8-week training regimen of stationary bicycling at 70% VO 2peak . Aerobic exercise training may, therefore, reduce the risk of hypertension in normotensive African-American males by the mechanism of a reduction in TPR. Because of the limited number of subjects, the results of this study should be interpreted cautiously pending confirmation by a larger controlled trial.

Effects of high-carbohydrate and high-fat dietary treatments on measures of heart rate variability and sympathovagal balance.

AIMS We tested the hypothesis that respiratory quotient (RQ) determines sympathovagal balance associated with metabolism of stored and dietary energy substrates. MAIN METHODS Six 18-20 year-old African-American males were studied after two control pretreatments of fasting and post-treatments of metabolizing high-fat and high-carbohydrate beverages. RQ, heart rate (HR), energy expenditure (EE) and blood pressure (BP) were recorded at rest and repeated 1 h-3 h after ingesting isocaloric high-carbohydrate and high-fat beverages. Sympathovagal modulation of HR was quantified by the low frequency/high frequency (LF/HF) ratio from fast Fourier transform (spectral) analysis of the electrocardiogram RR intervals during paced breathing at 0.2 Hz. Significance of differences of peak post-treatment values from controls was evaluated by analysis of covariance and of correlations by linear regression at P<0.05. KEY FINDINGS The high-carbohydrate and high-fat treatments increased RQ, EE, HR and LF/HF with significant interactions between covariates. LF/HF values were not significant after eliminating covariance of RQ, EE and HR for the control vs. high-fat and for the high-fat vs. high-carbohydrate and after eliminating covariance of EE and HR for the control vs. high-carbohydrate treatments. Across the RQ values, correlations were significant for EE and LF/HF. SIGNIFICANCE These findings imply that high RQ and sympathetic modulation produced by metabolizing carbohydrate is associated with high resting energy expenditure. We conclude that respiratory quotient may be an important determinant of the LF/HF ratio in the heart rate variability spectrum, likely, by a respiratory chemosensory mechanism.

Normal Exercise Blood Pressure Response in African-American Women with Parental History of Hypertension

Background:Genetic and environmental hypotheses may explain why normotensive persons at high risk of developing hypertension often exhibit greater cardiovascular reactivity to stressors than those at low risk. Methods:Pearson’s correlation was used to evaluate reproducibility and independent t test to compare the cardiovascular responses to 30 W of exercise of normotensive young adult African-American women with positive and negative parental histories (PH) of hypertension (PH+, n = 23; PH−, n = 20). Results:Correlations were significant for duplicate measurements. The effects of PH on blood pressure measured at rest and during exercise were not statistically significant (P > 0.1). A nearly significant trend for greater resting &OV0312;O2 (P = 0.08) was detected in the PH− than in the PH+ group (3.67 ± 0.18 versus 3.26 ± 0.14 mL/kg/min). Conclusion:A hyper-reactive blood pressure response to exercise, characteristic of the evolution of hypertension, may not be present among the normotensive female offspring of hypertensive African Americans. The significance of an 11% intergroup difference in the mean resting &OV0312;O2 observed in this study is unclear.

Blood pressure reactivity to mental stress and aerobic fitness in normotensive young adult African–American males with parental history of hypertension

Hypertension (HT) is the leading health problem in the adult African-American (AA) community and is associated with risk factors of stress, physical inactivity, and family history. We examined the influences of aerobic fitness and parental history of HT on blood pressure (BP) reactivity to mental stress in 60 normotensive young adult AA males. A 5-min mental arithmetic test was used as a provocative stress. Measurements of peak oxygen uptake (VO 2peak ) were used to classify physically active and inactive subjects into groups of high and low aerobic fitness. A questionnaire was used to evaluate parental BP histories. Reactivity of BP was indexed by differences in values (delta) measured during baseline and stress testing periods. Subjects with a parental history of HT (PH - ) had significantly higher baseline systolic BP and mean arterial BP (SBP, MABP) values than subjects with no parental history of HT (PH - ). Among the group of PH + subjects, BP reactivity to mental stress was as follows: the high aerobic fitness subgroup (VO 2peak = 54.6±1.2 ml/kg/min) (n = 15) exhibited a 7.3 ± 2.0 mmHg rise in SBP and a 3.2 ± 2.0 mmHg rise in MABP, and the low aerobic fitness subgroup (VO 2peak = 37.1 ± 0.7 ml/kg/min) (n = 15) had a 15.8 ± 2.0 mmHg rise in SBP and an 11.8 ± 2.0 mmHg rise in MABP (p<0.05), Among the group of PH - subjects with high and low aerobic fitness (n = 30, 15/group), no differences in BP reactivity to mental stress were found, These results suggest that a lifestyle of physical activity associated with a high level of aerobic fitness may attenuate BP reactivity to mental stress and reduce the risk of HT in AA men.