Relationship between aortic augmentation index and blood pressure during metaboreflex activation in healthy young men

Muscle metaboreflex adaptations to exercise training in health and disease

Abnormalities in the muscle metaboreflex concur to exercise intolerance and greater cardiovascular risk. Exercise training benefits neurocardiovascular function at rest and during exercise, but its role in favoring muscle metaboreflex in health and disease remains controversial. While some authors demonstrated that exercise training enhanced the sensitization of muscle metabolically afferents and improved neurocardiovascular responses to muscle metaboreflex activation, others reported unaltered responses. This narrative review aimed to: (a) highlight the current evidence on the effects of exercise training upon cardiovascular and autonomic responses to muscle metaboreflex activation; (b) analyze the role of training components and indicate potential mechanisms of metaboreflex adaptations; and (c) address key methodological features for future research. Though limited, accumulated evidence suggests that muscle metaboreflex adaptations depend on the individual clinical status, exercise modality, and training duration. In healthy populations, most trials negated the hypothesis of metaboreflex improvement due to chronic exercise, irrespective of the training duration. Favorable changes in patients with impaired metaboreflex, particularly chronic heart failure, mostly resulted from long-term interventions (> 16 weeks) including aerobic exercise of moderate to high intensity, performed in isolation or within multimodal training. Potential mechanisms of metaboreflex improvements include enhanced sensitivity of channels and receptors, greater antioxidant capacity, lower metabolite accumulation, increased functional sympatholysis, and muscle perfusion. Future research should investigate: (1) the dose-response relationship of training components within different exercise modalities to elicit improvements in individuals showing intact or impaired muscle metaboreflex; and (2) potential and specific underlying mechanisms of metaboreflex improvements in individuals with different medical conditions.

Exaggerated Aortic Pulse Pressure and Wave Amplitude During Muscle Metaboreflex Activation in Type 2 Diabetes Patients

BACKGROUND

Peripheral mean arterial pressure (MAP) responses to muscle metaboreflex activation using postexercise muscle ischemia (PEMI) in type 2 diabetes patients (T2D) are contradictory. Given that aortic pulse pressure (PP) and wave reflections are better indicators of cardiac load than peripheral MAP, we evaluated aortic blood pressure (BP) and wave amplitude during PEMI.

METHODS

Aortic BP and pressure wave amplitudes were measured at rest and during PEMI following isometric handgrip at 30% maximum voluntary contraction (MVC) in 16 T2D and 15 controls. Resting aortic stiffness (carotid-femoral pulse wave velocity, cfPWV) and fasting blood glucose (FBG) were measured.

RESULTS

Increases in aortic MAP (Δ26 ± 2 mmHg vs. Δ17 ± 2 mmHg), PP (Δ15 ± 2 mmHg vs. Δ10 ± 1 mmHg), augmentation index (AIx) (Δ8.2 ± 1.0% vs. Δ4.5 ± 1.3%), augmented pressure (AP) (Δ11 ± 1 mmHg vs. Δ5 ± 1 mmHg), forward (Pf) (Δ9 ± 1 mmHg vs. Δ5 ± 1 mmHg), and backward pressure waves (Pb) (Δ10 ± 1 mmHg vs. Δ5 ± 1 mmHg) responses to PEMI were greater in T2D than controls (P < 0.05). Aortic PP, but not MAP, response to PEMI was correlated to Pf (r = 0.63, P < 0.001) and Pb (r = 0.82, P < 0.001) responses and cfPWV (r = 0.37, P < 0.05).

CONCLUSIONS

Aortic BP and pressure wave responses to muscle metaboreflex activation are exaggerated in T2D. Aortic PP during PEMI was related to increased wave reflection, forward wave amplitude, and aortic stiffness in T2D patients.

Muscle metaboreflex activation via postexercise ischemia as a tool for teaching cardiovascular physiology for undergraduate students

The cardiovascular responses to exercise are mediated by several interactive neural mechanisms, including central command, arterial baroreflex, and skeletal muscle mechano- and metaboreflex. In humans, muscle metaboreflex activation can be isolated via postexercise ischemia (PEI), which increases sympathetic nerve activity and partially maintains the exercise-induced increase in arterial blood pressure. Here, we describe a practical laboratory class using PEI as a simple and useful technique to teach cardiovascular physiology. In an undergraduate exercise physiology class ( n = 47), a traditional 4-h lecture was conducted discussing the neural control mechanisms of cardiovascular regulation during exercise. Thereafter, eight students (4 men and 4 women) were selected to participate as a volunteer of a practical laboratory class. Each participant performed 90 s of isometric handgrip exercise at 40% of maximal voluntary contraction, followed by 3 min of PEI. Arterial blood pressure and heart rate were measured by digital monitors at rest and during isometric handgrip, PEI, and recovery. In addition, blood samples were collected from the tip of the exercising finger for blood lactate analyses. After the laboratory class, a survey was given to determine the perceptions of the students. The findings demonstrate that this laboratory class has proved to be highly popular with students, who self-reported a significant improvement in their understanding of several aspects of cardiovascular regulation during exercise.