Lack of age-associated elevations in 24-h systolic and pulse pressures in women who exercise regularly

Ageing and the Autonomic Nervous System

The vertebrate nervous system is divided into central (CNS) and peripheral (PNS) components. In turn, the PNS is divided into the autonomic (ANS) and enteric (ENS) nervous systems. Ageing implicates time-related changes to anatomy and physiology in reducing organismal fitness. In the case of the CNS, there exists substantial experimental evidence of the effects of age on individual neuronal and glial function. Although many such changes have yet to be experimentally observed in the PNS, there is considerable evidence of the role of ageing in the decline of ANS function over time. As such, this chapter will argue that the ANS constitutes a paradigm for the physiological consequences of ageing, as well as for their clinical implications.

Sex differences in mechanisms of arterial stiffness

Arterial stiffness progressively increases with aging and is an independent predictor of cardiovascular disease (CVD) risk. Evidence supports that there are sex differences in the time course of aging-related arterial stiffness and the associated CVD risk, which increases disproportionately in postmenopausal women. The association between arterial stiffness and mortality is almost twofold higher in women versus men. The differential clinical characteristics of the development of arterial stiffness between men and women indicate the involvement of sex-specific mechanisms. This review summarizes the current literature on sex differences in vascular stiffness induced by aging, obesity, hypertension, and sex-specific risk factors as well as the impact of hormonal status, diet, and exercise on vascular stiffness in males and females. An understanding of the mechanisms driving sex differences in vascular stiffness has the potential to identify novel sex-specific therapies to lessen CVD risk, the leading cause of death in males and females. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Influence of single bout of aerobic exercise on aortic pulse pressure

PURPOSE

Regular aerobic exercise has come to the forefront of non-pharmacological treatment for hypertension. In this line, post-exercise hypotension may have a potential tool for efficient blood pressure management. However, less is known about the influence of acute aerobic exercise on aortic pulse pressure (PP), an important property underlying the pathophysiology of cardiovascular disease. We tested the hypotheses that aortic PP would be attenuated with a single aerobic exercise and that its extent would be associated with the delayed return of reflected wave and the leg vasodilatory capacity.

METHODS

In 23 apparent healthy men (22 ± 4 years), hemodynamic variables and aortic pulse wave velocity (PWV) were measured before and 20 and 50 min after a 60-min bout of cycling exercise at moderate intensity (corresponding to 65-75 % heart rate reserve). Aortic pressure was estimated from applanation tonometrically measured radial arterial pressure waveform via general transfer function. Peak calf vascular dilatory capacity was measured with the ischemic exercise-induced hyperemia (via venous occlusion plethysmography).

RESULTS

Finger, brachial, and aortic PP were significantly attenuated following the exercise. At 20 min after the exercise cessation, individual changes in aortic PWV significantly correlated with corresponding changes in aortic PP (r = 0.541, P < 0.05), but this correlation was no longer significant at 50 min after the exercise cessation. Peak calf vascular dilatory capacity was not associated with change in aortic PP.

CONCLUSIONS

We conclude that in young men the aortic PP would be attenuated with the moderate-intensity dynamic exercise partly due to the delayed return of reflection wave from periphery.

Edward F. Adolph Distinguished Lecture: The remarkable anti-aging effects of aerobic exercise on systemic arteries

Cardiovascular diseases (CVD) remain the leading cause of morbidity and mortality in modern societies, and advancing age is the major risk factor for CVD. Arterial dysfunction, characterized by large elastic artery stiffening and endothelial dysfunction, is the key event leading to age-associated CVD. Our work shows that regular aerobic exercise inhibits large elastic artery stiffening with aging (optimizes arterial compliance) and preserves endothelial function. Importantly, among previously sedentary late middle-aged and older adults, aerobic exercise improves arterial stiffness and enhances endothelial function in most groups and, therefore, also can be considered a treatment for age-associated arterial dysfunction. The mechanisms by which regular aerobic exercise destiffens large elastic arteries are incompletely understood, but existing evidence suggests that reductions in oxidative stress associated with decreases in both adventitial collagen (fibrosis) and advanced glycation end-products (structural protein cross-linking molecules), play a key role. Aerobic exercise preserves endothelial function with aging by maintaining nitric oxide bioavailability via suppression of excessive superoxide-associated oxidative stress, and by inhibiting the development of chronic low-grade vascular inflammation. Recent work from our laboratory supports the novel hypothesis that aerobic exercise may exert these beneficial effects by directly inducing protection to aging arteries against multiple adverse factors to which they are chronically exposed. Regular aerobic exercise should be viewed as a "first line" strategy for prevention and treatment of arterial aging and a vital component of a contemporary public health approach for reducing the projected increase in population CVD burden.

Vascular health in the ageing athlete

The demographics of ageing are changing dramatically such that there will be many more older adults in the near future. This setting is projected to produce a new 'boomer-driven' epidemic of physiological dysfunction, disability and risk of chronic degenerative disorders, including cardiovascular diseases. Standing out against this dreary biomedical forecast are Masters athletes, a group of middle-aged and older adults who engage in regular vigorous physical training and competitive sport. Compared with their sedentary/less active (untrained) peers, Masters athletes who perform endurance training-based activities demonstrate a more favourable arterial function-structure phenotype, including lower large elastic artery stiffness, enhanced vascular endothelial function and less arterial wall hypertrophy. As such, they may represent an exemplary model of healthy or 'successful' vascular ageing. In contrast, Masters athletes engaged primarily/exclusively in intensive resistance training exhibit less favourable arterial function-structure than their endurance-trained peers and, in some instances, untrained adults. These different arterial properties are probably explained in large part by the different intravascular mechanical forces generated during endurance versus resistance exercise-related training activities. The more favourable arterial function-structure profile of Masters endurance athletes may contribute to their low risk of clinical cardiovascular diseases.

Distal shift of arterial pressure wave reflection sites with aging

An early return of reflected waves, the backward propagation of the arterial pressure wave from the periphery to the heart, is associated with the augmentation of central pulse pressure and cardiovascular risks. The locations of arterial pressure wave reflection, along with arterial stiffening, have a major influence on the timing of the reflected wave. To determine the influence of aging on the location of a major reflection site, arterial length (via 3D artery tracing of MRI) and central (carotid-femoral) and peripheral (femoral-ankle) pulse wave velocities were measured in 208 adults varying in age. The major reflection site was detected by carotid-femoral pulse wave velocity and the reflected wave transit time (via carotid arterial pressure wave analysis). The length from the aortic valve to the major reflection site (eg, effective reflecting length) significantly increased with aging. The effective reflecting length normalized by the arterial length demonstrated that the major reflection sites were located between the aortic bifurcation and femoral site in most of the subjects. The normalized effective reflecting length did not alter with aging until 65 years of age and increased remarkably thereafter in men and women. The effective reflecting length was significantly and positively associated with the difference between central and peripheral pulse wave velocities (r=0.76). This correlation remained significant even when the influence of aortic pulse wave velocity was partial out (r=0.35). These results suggest that the major reflection site shifts distally with aging partly because of the closer matching of impedance provided by central and peripheral arterial stiffness.

Resistance Training Effects on Arterial Compliance in Premenopausal Women

Endurance training has been shown to increase arterial compliance; however, the effect of resistance training is unclear. Purpose: The purpose of this study was to examine the effect lower body resistance training on arterial compliance in healthy premenopausal women. Methods: Thirty-two women were assigned to a resistance training group (n = 21) or a control group (n = 11). Large (C1) and small (C2) arterial compliance (Pulse Contour Analysis) were measured at baseline and after twelve weeks of training. Results: Two-way (group × time) repeated measured ANOVA did not detect significant group, time effects or group × time interactions for small arterial compliance (P > 0.05). There was a significant time effect for large arterial compliance (P < 0.05), which increased in both groups. Conclusions: In contrast to previous studies in men, which found decrease in arterial compliance with resistance training, no decrease in arterial compliance was observed.

Habitual exercise and arterial aging

Aging affects the function and structure of arteries and increases the risk of cardiovascular diseases (CVD). In healthy sedentary adults, aging is associated with increased stiffness (reduced compliance) of large elastic arteries; impaired vascular endothelial function, including reductions in endothelium-dependent dilation (EDD), release of tissue-type plasminogen activator (fibrinolytic capacity) and endothelial progenitor cell number and function; increased intima-media wall thickness (IMT); and peripheral vasoconstriction (decreased basal leg blood flow). Habitual physical activity/increased aerobic exercise capacity is associated with reduced risk of CVD. Compared with their sedentary peers, adults who regularly perform aerobic exercise demonstrate smaller or no age-associated increases in large elastic artery stiffness, reductions in vascular endothelial function, and increases in femoral artery IMT. A short-term, moderate-intensity aerobic exercise intervention (brisk daily walking for 12 wk) improves carotid artery compliance and can restore vascular endothelial function in previously sedentary middle-aged and older adults. Reduced oxidative stress may be an important mechanism contributing to these effects. Habitual resistance exercise increases (high-intensity) or does not affect (moderate-intensity) large elastic artery stiffness, and prevents/restores the age-associated reduction in basal leg blood flow independent of changes in leg fat-free mass. Habitual exercise favorably modulates several expressions of arterial aging, thus preserving vascular function and possibly reducing the risk of CVD.

Effect of aging on baroreflex function in humans

Arterial blood pressure (BP) is regulated via the interaction of various local, humoral, and neural factors. In humans, the major neural pathway for acute BP regulation involves the baroreflexes. In response to baroreceptor activation/deactivation, as occurs during transient changes in BP, key determinants of BP, such as cardiac period/heart rate (via the sympathetic and parasympathetic nervous system) and vascular resistance (via the sympathetic nervous system), are modified to maintain BP homeostasis. In this review, the effects of aging on both the parasympathetic and sympathetic arms of the baroreflex are discussed. Aging is associated with decreased cardiovagal baroreflex sensitivity (i.e., blunted reflex changes in R-R interval in response to a change in BP). Mechanisms underlying this decrease may involve factors such as increased levels of oxidative stress, vascular stiffening, and decreased cardiac cholinergic responsiveness with age. Consequences of cardiovagal baroreflex impairment may include increased levels of BP variability, an impaired ability to respond to acute challenges to the maintenance of BP, and increased risk of sudden cardiac death. In contrast, baroreflex control of sympathetic outflow is not impaired with age. Collectively, changes in baroreflex function with age are associated with an impaired ability of the organism to buffer changes in BP. This is evidenced by the reduced potentiation of the pressor response to bolus infusion of a pressor drug after compared to before systemic ganglionic blockade in older compared with young adults.

Blood pressure responses to lifestyle physical activity among young, hypertension-prone African-American women

BACKGROUND

Physical inactivity and obesity increase the risk for hypertension, and both are more prevalent in African-American than Caucasian women. Regular physical activity serves as an important intervention for reducing cardiovascular risk, yet the ideal physical activity profile to meet the needs of young, sedentary African-American women remains unclear. We performed a randomized, parallel, single-blind study to examine the effect of lifestyle physical activity (LPA) on blood pressure indices in sedentary African-American women aged 18 to 45 years with prehypertension or untreated stage 1 hypertension.

METHODS

The primary intervention was an 8-week individualized, home-based program in which women randomized to Exercise (n = 14) were instructed to engage in lifestyle-compatible physical activity (eg, walking, stair climbing) for 10 minutes, 3 times a day, 5 days a week, at a prescribed heart rate corresponding to an intensity of 50% to 60% heart rate reserve. Women in the No Exercise group (n = 10) continued with their usual daily activities. Mean changes in cuff, ambulatory, and pressure load indices were compared using paired t tests, and physical activity adherence was expressed as percentages.

RESULTS

Women in the Exercise group had a significant reduction in systolic blood pressure (-6.4 mm Hg, P = .036), a decrease in diastolic blood pressure status to the prehypertensive level (90.8 vs 87.4 mm Hg), and greater reductions in nighttime pressure load compared with the No Exercise group. Adherence to LPA was exceedingly high by all measures (65%-98%) and correlated with change in systolic blood pressure (r = -0.620, P = .024).

CONCLUSION

The accumulation of LPA reduced cuff, ambulatory, and pressure load. The accumulation of LPA appears well tolerated and feasible in this sample of young African-American women, demonstrated by the overall high adherence rates. Given the excess burden of pressure-related clinical sequelae among African Americans and the strong correlation between pressure load and target organ damage, LPA may represent a practical and effective strategy in this population.

Is autonomic support of arterial blood pressure related to habitual exercise status in healthy men?

We determined if the tonic autonomic nervous system (ANS) contribution to arterial blood pressure (BP) maintenance in humans is related to habitual endurance exercise status. Twenty-three healthy young (age 18-31 years) males, 11 endurance exercise-trained and 12 untrained, were studied. Maximal oxygen consumption was higher (P < 0.001) and resting heart rate and body fatness were lower (P < 0.05) in the exercise-trained men. Plasma noradrenaline concentrations and BP decreased from baseline levels in response to ganglionic blockade (intravenous trimethaphan) in both groups (all P < 0.001). The absolute (Delta mmHg: systolic = -35 +/- 2 vs. -32 +/- 4; diastolic = -13 +/- 2 vs. -10 +/- 2; mean = -21 +/- 2 vs. -17 +/- 3) and relative (Delta%: systolic = -35 +/- 2 vs. -31 +/- 3; diastolic = -26 +/- 3 vs. -20 +/- 3; mean = -31 +/- 2 vs. -26 +/- 3) decreases in BP were not significantly different between the endurance-trained and untrained men. There were no significant group differences in the heart rate, stroke volume, cardiac output or systemic vascular resistance (conductance) responses to trimethaphan. Systemic vascular alpha-adrenergic sensitivity (slope of the increase in mean BP with incremental phenylephrine infusion during ganglionic blockade) also did not differ in the two groups (endurance-trained: 3.2 +/- 0.5; untrained: 3.2 +/- 0.7 mmHg (ng phenylephrine)(-1) (ml plasma)(-1)). In the pooled sample, the decrease in mean BP during trimethaphan was related to baseline and changes in plasma noradrenaline concentrations (r = 0.58-0.65, P < 0.001) and alpha-adrenergic sensitivity (r = 0.49, P < 0.02). Our results suggest that the endurance exercise-trained state is not obviously associated with altered ANS support of BP in healthy young men. Basal sympathetic nervous system (SNS) activity and alpha-adrenergic vascular sensitivity are significant physiological correlates of ANS support of BP in this population.

Exercise and hypertension

Epidemiologic studies have consistently revealed inverse associations between physical activity (or fitness) and hypertension. There are hypotensive benefits to exercise training found across a number of aerobic and progressive resistance training modalities. Optimal exercise prescriptions remain unclear, but hypotensive benefits have been noted for mild to vigorous ranges of exercise intensity, for as few as three exercise sessions per week and durations as short as 20 minutes. Hypertensive subjects appear to experience greater reductions than normotensive subjects. Exercise interventions may be safely and effectively used with mild to moderate as well as severe levels of hypertension. The incorporation of physical activity with other lifestyle interventions provides multiple benefits to hypertensive patients that extend beyond a reduction in blood pressure.

Regular aerobic exercise modulates age-associated declines in cardiovagal baroreflex sensitivity in healthy men

1. Cardiovagal baroreflex sensitivity (BRS), the arterial baroreflex-mediated change in the R-R interval per unit change in systolic blood pressure, decreases with advancing age in sedentary adult humans. We determined the effects of regular aerobic exercise on the age-related decline in cardiovagal BRS. 2. In the cross-sectional study, 133 healthy men 18-79 years of age who were either sedentary, performing moderate aerobic exercise, or endurance exercise trained were studied. Among the sedentary men, cardiovagal BRS (phase IV of Valsalva's manoeuvre) was progressively lower (P < 0.05) in the middle-aged ( approximately 33 %) and older ( approximately 60 %) groups compared with the young group. In contrast, cardiovagal BRS was similar in the young and middle-aged men in the moderate exercise and endurance-trained groups. Cardiovagal BRS was lower (P < 0.05) in the older exercising men, but the magnitude of decline across age ( approximately 30 %) was only half as great as that in sedentary men. Cardiovagal BRS was 40-75 % greater (P < 0.05) in middle-aged and older men who exercised regularly compared with their sedentary peers. 3. In the intervention study, a 3 month aerobic exercise intervention (primarily walking) increased cardiovagal BRS by an average of 25 % (P < 0.05) in 13 previously sedentary middle-aged and older (56 +/- 1 years) healthy men. 4. Our results demonstrate for the first time that regular aerobic exercise: (1) attenuates the age-associated decline in cardiovagal BRS; and (2) partially restores the loss of cardiovagal BRS in previously sedentary middle-aged and older healthy men.