Aging exaggerates blood pressure response to ischemic rhythmic handgrip exercise in humans

Associating frailty and dynamic dysregulation between motor and cardiac autonomic systems

Frailty is a geriatric syndrome associated with the lack of physiological reserve and consequent adverse outcomes (therapy complications and death) in older adults. Recent research has shown associations between heart rate (HR) dynamics (HR changes during physical activity) with frailty. The goal of the present study was to determine the effect of frailty on the interconnection between motor and cardiac systems during a localized upper-extremity function (UEF) test. Fifty-six individuals aged 65 or above were recruited and performed the previously developed UEF test consisting of 20-s rapid elbow flexion with the right arm. Frailty was assessed using the Fried phenotype. Wearable gyroscopes and electrocardiography were used to measure motor function and HR dynamics. In this study, the interconnection between motor (angular displacement) and cardiac (HR) performance was assessed, using convergent cross-mapping (CCM). A significantly weaker interconnection was observed among pre-frail and frail participants compared to non-frail individuals (p < 0.01, effect size = 0.81 ± 0.08). Using logistic models, pre-frailty and frailty were identified with sensitivity and specificity of 82%-89%, using motor, HR dynamics, and interconnection parameters. Findings suggested a strong association between cardiac-motor interconnection and frailty. Adding CCM parameters in a multimodal model may provide a promising measure of frailty.

Age-related alterations in the cardiovascular responses to acute exercise in males and females: role of the exercise pressor reflex

Autonomic adjustments of the cardiovascular system are critical for initiating and sustaining exercise by facilitating the redistribution of blood flow and oxygen delivery to meet the metabolic demands of the active skeletal muscle. Afferent feedback from active skeletal muscles evokes reflex increases in sympathetic nerve activity and blood pressure (BP) (i.e., exercise pressor reflex) and contributes importantly to these primary neurovascular adjustments to exercise. When altered, this reflex contributes significantly to the exaggerated sympathetic and BP response to exercise observed in many cardiovascular-related diseases, highlighting the importance of examining the reflex and its underlying mechanism(s). A leading risk factor for the pathogenesis of cardiovascular disease in both males and females is aging. Although regular exercise is an effective strategy for mitigating the health burden of aging, older adults face a greater risk of experiencing an exaggerated cardiovascular response to exercise. However, the role of aging in mediating the exercise pressor reflex remains highly controversial, as conflicting findings have been reported. This review aims to provide a brief overview of the current understanding of the influence of aging on cardiovascular responses to exercise, focusing on the role of the exercise pressor reflex and proposing future directions for research. We reason that this review will serve as a resource for health professionals and researchers to stimulate a renewed interest in this critical area.

Exaggerated exercise pressor reflex in male UC Davis type 2 diabetic rats is due to the pathophysiology of the disease and not aging

Introduction: Studies in humans and animals have found that type 2 diabetes mellitus (T2DM) exaggerates the blood pressure (BP) response to exercise, which increases the risk of adverse cardiovascular events such as heart attack and stroke. T2DM is a chronic disease that, without appropriate management, progresses in severity as individuals grow older. Thus, it is possible that aging may also exaggerate the BP response to exercise. Therefore, the purpose of the current study was to determine the effect of the pathophysiology of T2DM on the exercise pressor reflex independent of aging. Methods: We compared changes in peak pressor (mean arterial pressure; ΔMAP), BP index (ΔBPi), heart rate (ΔHR), and HR index (ΔHRi) responses to static contraction, intermittent contraction, and tendon stretch in UCD-T2DM rats to those of healthy, age-matched Sprague Dawley rats at three different stages of the disease. Results: We found that the ΔMAP, ΔBPi, ΔHR, and ΔHRi responses to static contraction were significantly higher in T2DM rats (ΔMAP: 29 ± 4 mmHg; ΔBPi: 588 ± 51 mmHg•s; ΔHR: 22 ± 5 bpm; ΔHRi: 478 ± 45 bpm•s) compared to controls (ΔMAP: 10 ± 1 mmHg, p < 0.0001; ΔBPi: 121 ± 19 mmHg•s, p < 0.0001; ΔHR: 5 ± 2 bpm, p = 0.01; ΔHRi: 92 ± 19 bpm•s, p < 0.0001) shortly after diabetes onset. Likewise, the ΔMAP, ΔBPi, and ΔHRi to tendon stretch were significantly higher in T2DM rats (ΔMAP: 33 ± 7 mmHg; ΔBPi: 697 ± 70 mmHg•s; ΔHRi: 496 ± 51 bpm•s) compared to controls (ΔMAP: 12 ± 5 mmHg, p = 0.002; ΔBPi: 186 ± 30 mmHg•s, p < 0.0001; ΔHRi: 144 ± 33 bpm•s, p < 0.0001) shortly after diabetes onset. The ΔBPi and ΔHRi, but not ΔMAP, to intermittent contraction was significantly higher in T2DM rats (ΔBPi: 543 ± 42 mmHg•s; ΔHRi: 453 ± 53 bpm•s) compared to controls (ΔBPi: 140 ± 16 mmHg•s, p < 0.0001; ΔHRi: 108 ± 22 bpm•s, p = 0.0002) shortly after diabetes onset. Discussion: Our findings suggest that the exaggerated exercise pressor reflex and mechanoreflex seen in T2DM are due to the pathophysiology of the disease and not aging.

The exercise pressor reflex: An update

The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.