Sae Young Jae

Racial differences in central blood pressure and vascular function in young men

Young African-American men have altered macrovascular and microvascular function. In this cross-sectional study, we tested the hypothesis that vascular dysfunction in young African-American men would contribute to greater central blood pressure (BP) compared with young white men. Fifty-five young (23 yr), healthy men (25 African-American and 30 white) underwent measures of vascular structure and function, including carotid artery intima-media thickness (IMT) and carotid artery beta-stiffness via ultrasonography, aortic pulse wave velocity, aortic augmentation index (AIx), and wave reflection travel time (Tr) via radial artery tonometery and a generalized transfer function, and microvascular vasodilatory capacity of forearm resistance arteries with strain-gauge plethysmography. African-American men had similar brachial systolic BP (SBP) but greater aortic SBP (P<0.05) and carotid SBP (P<0.05). African-American men also had greater carotid IMT, greater carotid beta-stiffness, greater aortic stiffness and AIx, reduced aortic Tr and reduced peak hyperemic, and total hyperemic forearm blood flow compared with white men (P<0.05). In conclusion, young African-American men have greater central BP, despite comparable brachial BP, compared with young white men. Diffuse macrovascular and microvascular dysfunction manifesting as carotid hypertrophy, increased stiffness of central elastic arteries, heightened resistance artery constriction/blunted resistance artery dilation, and greater arterial wave reflection are present at a young age in apparently healthy African-American men, and conventional brachial BP measurement does not reflect this vascular burden.

Physical fitness predicts functional tasks in individuals with Down syndrome.

UNLABELLED Individuals with Down syndrome (DS) exhibit reduced strength and aerobic capacity, which may limit their ability to perform functional tasks of daily living. PURPOSE This study was conducted to examine the relationship between timed performance on functional tasks of daily living and age, knee isometric strength, and peak aerobic capacity in a group of individuals with DS. METHODS This was a cross-sectional study involving 35 individuals (27 +/- 7.5 yr) with DS. Participants completed an isometric test of knee extensor and flexor strength, an individualized exercise test to measure peak aerobic capacity, and three timed functional tasks of daily living, which included chair rise, gait speed, and stair ascent and descent. Multiple regression analyses were performed to examine the relationship between timed task performance and age, knee isometric strength, and peak aerobic capacity. RESULTS The multiple regression models explained 11-29% of the variance in timed task performance. Knee extensor strength was the most influential variable in predicting timed task performance (squared semipartial correlation coefficient [sr2] = 0.11-0.20), followed by aerobic capacity (sr2 = 0.10-0.14). Age was not a significant predictor of timed task performance. CONCLUSION These findings suggest that physical fitness (defined here as aerobic capacity and knee extensor strength) limits the ability of adults with DS to perform functional tasks of daily living. Randomized controlled trials should be performed to test the probable causal relationship between exercises designed to improve physical fitness and functional tasks of daily living.

Resistance exercise training reduces central blood pressure and improves microvascular function in African American and white men

OBJECTIVE African American men have stiffer large central arteries and impaired dilation of smaller peripheral arteries when compared to their white peers. The purpose of this study was to examine the effect of resistance exercise training (RT) on vascular function and central blood pressure (BP) in young (22 years) African American and white men. METHODS Vascular and hemodynamic measures were made in 19 African American and 18 white men at baseline and following 6-weeks of RT. Carotid BP and carotid/brachial artery beta-stiffness were measured by tonometry and ultrasonography, respectively. Aortic BP was measured by radial artery tonometry and a generalized transfer function. Aortic stiffness was measured by pulse wave velocity (PWV). Forearm blood flow (FBF) was measured by strain-gauge plethysmography before and during reactive hyperemia (RH) induced by 5-min of brachial artery occlusion. RESULTS There were similar reductions in central BP and similar increases in FBF-RH in both African American and white men following RT (p<0.05). There were no changes in brachial systolic BP, carotid stiffness, and aortic PWV in either group (p>0.05). There was an increase in brachial stiffness in African American but not white men following RT (p<0.05). CONCLUSIONS RT led to reductions in central BP and increases in microvascular endothelial function with no effect on central artery stiffness in both groups of young men. RT increased brachial stiffness in African American men. Measurement of conventional brachial BP does not capture the central hemodynamic and vascular response to exercise training due to disparate racial changes in regional vascular properties.

Exaggerated blood pressure response to exercise is associated with carotid atherosclerosis in apparently healthy men.

Objective Although an exaggerated systolic blood pressure (SBP) response to exercise is a predictor of future hypertension and cardiovascular mortality, the underlying mechanisms are not fully understood. We tested the hypothesis that an exaggerated SBP response is associated with carotid atherosclerosis in a cross-sectional study of 9073 healthy men (aged 47.8 ± 8.8 years). Methods Exaggerated SBP response was defined as an SBP of 210 mmHg or greater during a maximal treadmill test. Carotid atherosclerosis was defined as stenosis greater than 25% or intima–media thickness greater than 1.2 mm using B-mode ultrasonography. Results An exaggerated SBP response was present in 375 men (4.1%). The proportion of individuals with carotid atherosclerosis in the group with an exaggerated SBP response to exercise was higher than in the group with a normal SBP response (14.4 versus 5.3%, P < 0.001). In a multivariable logistic regression model, individuals with an exaggerated SBP (≥ 210 mmHg) response to exercise had a 2.02 times [95% confidence interval (CI) 1.33–3.05] increased risk of carotid atherosclerosis compared with individuals with an SBP response of less than 210 mmHg. The highest quartile (> 61 mmHg) group of relative exercise-induced increases in SBP showed a 1.57 (95% CI 1.18–2.08) greater risk of carotid atherosclerosis compared with individuals in the lowest quartile (< 38 mmHg) in the adjusted model. Conclusions These results suggest that an exaggerated SBP response to exercise is strongly associated with carotid atherosclerosis, independent of established risk factors in healthy men. It may be an important factor in evaluating hypertension related to target-organ damage.

C-reactive protein and cardiac vagal activity following resistance exercise training in young African-American and white men

African Americans have a greater prevalence of hypertension and diabetes compared with white Americans, and both autonomic dysregulation and inflammation have been implicated in the etiology of these disease states. The purpose of this study was to examine the cardiac autonomic and systemic inflammatory response to resistance training in young African-American and white men. Linear (time and frequency domain) and nonlinear (sample entropy) heart rate variability, baroreflex sensitivity, tonic and reflex vagal activity, and postexercise heart rate recovery were used to assess cardiac vagal modulation. C-reactive protein (CRP) and white blood cell count were used as inflammatory markers. Twenty two white and 19 African-American men completed 6 wk of resistance training followed by 4 wk of exercise detraining (Post 2). Sample entropy, tonic and reflex vagal activity, and heart rate recovery were increased in white and African-American men following resistance training (P < 0.05). Following detraining (Post 2), sample entropy, tonic and reflex vagal activity, and heart rate recovery returned to baseline values in white men but remained above baseline in African-American men. While there were no changes in white blood cell count or CRP in white men, these inflammatory markers decreased in African-American men following resistance training, with reductions being maintained following detraining (P < 0.05). In conclusion, resistance training improves cardiac autonomic function and reduces inflammation in African-American men, and these adaptations remained after the cessation of training. Resistance training may be an important lifestyle modification for improving cardiac autonomic health and reducing inflammation in young African-American men.

The effect of progressive resistance training on leg strength, aerobic capacity and functional tasks of daily living in persons with Down syndrome

Purpose. The purpose of this study was to examine the effect of progressive resistance training on leg strength, aerobic capacity and physical function in persons with Down syndrome (DS). Method. Thirty persons with DS (age 28 SD 8 years) were assigned to an intervention or control group. The intervention group performed resistance training 2 days per week for 10 weeks. Participants performed tests to measure isometric and isokinetic knee extensor and flexor peak torque, peak aerobic capacity and timed performance on chair rise, walking and stair ascent and descent. Result. Persons with DS receiving the intervention significantly increased their isokinetic knee extensor and flexor peak torque [[Absolute change (post minus pre-value) was 17.0 SD 29.6 and 12.6 SD 18.9 N m, respectively]] and isometric knee extensor peak torque at angles of 45° (2.9 SD 23.2 N m), 60° (3.0 SD 22.9 N m) and 75° (14.2 SD 30.0 N m). These changes were significantly greater than in the control group. In addition, the time to ascend (−0.3 SD 0.8 s) and descend (−0.6 SD 0.9 s) stairs significantly decreased in the intervention group compared to the control group. Conclusion. These findings show that progressive resistance training is an effective intervention for persons with DS to improve leg strength and stair-climbing ability.

Muscular strength is inversely associated with aortic stiffness in young men.

UNLABELLED Muscular strength is associated with reduced mortality. Paradoxically, strength training may increase central artery stiffness, a predictor of cardiovascular morbidity and mortality. However, the relationship between muscular strength and central arterial stiffness has yet to be defined. PURPOSE The purpose of this study was to determine the relationship between muscular strength and central arterial stiffness in young men. METHODS Central and peripheral pulse wave velocity (PWV), augmentation index, muscular strength, and aerobic capacity (V O2peak) were measured in 79 young men (mean +/- SD, age = 23 +/- 4 yr). Height, weight, and brachial blood pressure were also recorded. Muscular strength was determined using a one-repetition maximum bench press and normalized to bodyweight. Spearman correlations were used to determine the relationships between relative strength, aerobic fitness, and hemodynamic/vascular measures. RESULTS There was a significant negative correlation between central PWV and strength (r = -0.222, P < 0.05). The relationship remained significant when controlling for aerobic fitness (r = -0.189, P < 0.05). Muscular strength was significantly higher (P < 0.05) in men with low central PWV (5.2 +/- 0.4 m.s) compared with men with high central PWV (6.6 +/- 0.4 m.s). CONCLUSION These results show that there is a significant inverse association between muscular strength and aortic stiffness independent of aerobic fitness.

Effects of acute resistance exercise on arterial stiffness in young men.

Background and Objectives Increased central arterial stiffness is an emerging risk factor for cardiovascular disease. Acute aerobic exercise reduces arterial stiffness, while acute resistance exercise may increase arterial stiffness, but this is not a universal finding. We tested whether an acute resistance exercise program was associated with an increase in arterial stiffness in healthy young men. Subjects and Methods Thirteen healthy subjects were studied under parallel experimental conditions on 2 separate days. The order of experiments was randomized between resistance exercise (8 resistance exercises at 60% of 1 repeated maximal) and sham control (seated rest in the exercise room). Carotid-femoral pulse wave velocity (PWV) and aortic augmentation index as indices of aortic stiffness were measured using applanation tonometry. Measurements were made at baseline before treatments, 20 minutes, and 40 minutes after treatments (resistance exercise and sham control). Results There was no difference in resting heart rate or in arterial stiffness between the two experimental conditions at baseline. At 20 minutes after resistance exercise, heart rate, carotid-femoral PWV and augmentation index@75(%) were significantly increased in the resistance exercise group compared with the sham control (p<0.05). Brachial blood pressure, central blood pressure and pulse pressure were not significantly increased after resistance exercise. Conclusion An acute resistance exercise program can increase arterial stiffness in young healthy men. Further studies are needed to clarify the effects of long-term resistance training on arterial stiffness.

Complexity of force output during static exercise in individuals with Down syndrome

Force variability is greater in individuals with Down syndrome (DS) compared with persons without DS and is similar to that seen with normal aging. The purpose of this study was to examine the structure (in both time and frequency domains) of force output variability in persons with DS to determine whether deficits in force control are similar between individuals with DS and older adults. An isometric handgrip task at a constant force (30% of maximal voluntary contraction) was completed by individuals with DS (n = 29, age 26 yr), and healthy young (n = 26, age 27 yr) and older (n = 33, age 70 yr) individuals. Mean, standard deviation (SD), and coefficient of variation (CV) were used to analyze the magnitude of force output variability. Spectral analysis and approximate entropy (ApEn) were used to analyze the structure of force output variability. Mean force output for DS was lower than in young controls (P < 0.05) but no different from old controls. Individuals with DS had greater SD and CV than young and old controls (P < 0.05). The DS group had a significantly greater proportion of spectral power within the 0-to 4-Hz bandwidth than the young and older controls (P < 0.05). The DS group had significantly lower ApEn values than the young controls (P < 0.05), but there were no differences in ApEn between the DS group and the old controls (P > 0.05). In conclusion, young persons with DS demonstrate enhanced temporal structure and greater amplitude of low-frequency oscillations in the force output signal than age-matched non-DS peers. Interestingly, young persons with DS and older persons without DS have similar time-dependent structure of force output variability. This would suggest a possible link between premature aging and less complex force output in persons with DS.

Association between cardiorespiratory fitness and arterial stiffness in men with the metabolic syndrome

AIMS We tested the hypothesis that high cardiorespiratory fitness (fitness) is associated with lower levels of arterial stiffness in 1035 (age 52 ± 6 years) men with and without the metabolic syndrome. METHODS Arterial stiffness was derived from brachial-ankle pulse wave velocity (baPWV). Fitness was directly measured by peak oxygen uptake during a standard treadmill test. RESULTS Men with the metabolic syndrome (n = 168) had significantly higher baPWV than men without the metabolic syndrome (1424 ± 175 cm/s vs. 1333 ± 150 cm/s, p < 0.05). When separated according to quartiles of fitness, men with and without the metabolic syndrome in the highest quartile of fitness had significantly lower baPWV compared to men in the lowest quartile of fitness (p < 0.05). Fitness was inversely correlated with baPWV in men with (p = -0.29, p < 0.05) and without the metabolic syndrome (p = -0.22, p < 0.05). There was no differences in baPWV levels between fit men with the metabolic syndrome and unfit men without the metabolic syndrome (fit/MetS; 1366 ± 140 vs. unfit/no MetS; 1401 ± 194 cm/s, p = 0.81). CONCLUSIONS These results demonstrate that high fitness is inversely associated with arterial stiffness in men with and without the metabolic syndrome. Increased arterial stiffness in the metabolic syndrome is attenuated by high fitness.