Exercise Pressor Reflex: Mechanisms, Components And Effects

Exercise pressor reflex has the ability to enhance exercise performance of an individual by enhancing the activities of sympathetic nervous system. It helps to bring about cardiovascular changes through reflex action within the individual. It mainly occurs when the skeletal muscles contract due to excessive exercise. Wan et al. (2020) states that the cardiovascular responses are determined by 3 control mechanisms- central command, baroreflex and exercise pressor reflex. Out of these, the exercise pressor reflex is triggered by the underlying physiological factors that consist of mechano and metabo reflexes. Group III and IV afferents are mainly involved during this activity. Grotle et al. (2020) have described the process in details through their study. Muscle contraction due to reception of stimulus occurs in case of mechano reflex action while formation of metabolic byproducts in muscles trigger metabo reflex action. Thus, this essay delves deep into the mechanism, components and effects of the exercise pressor reflex.

Exercise pressor reflex plays a vital role in increasing arterial blood pressure by enhancing the sympathetic nervous system activity leading to several cardiovascular changes. Grotle et al. (2020) states that the alterations of autonomic nervous system occur during exercise to maintain the metabolic needs of the muscles. Excessive vasodilation occurs within the working muscles preventing lowering of blood pressure.

The pressor reflex stimulated by exercise helps in circulation of blood, increases the sympathetic activity and decreases the parasympathetic activity of the body. Muscles respond to different kinds of stimuli, that is, mechanical stimuli and metabolic stimuli. As per the findings of Grotle et al. (2020), group III myelinated afferents are found to respond to the mechanical one while the unmyelinated group IV afferents respond to the metabolic ones. Thus, the authors noted two components of exercise pressor reflex, that is, mechanoreflex and metaboreflex, that are stimulated by rhythmic or intermittent muscle contraction and metabolic byproducts respectively. Components Of The Exercise Pressor Reflex Example Paper

Both high and low level of exercise have been found to generate reflexes. Grotle et al. (2020) observed that the muscle mass amount, intensity and mode of exercise have significant influence on exercise pressor reflex. Low cardiovascular responses are evoked by rhythmic exercise while more cardiovascular responses are noticed in case of isometric exercise. As it exacerbates the blood pressure response, it might be a threat to people with compromised cardiovascular health, as appropriate cardiovascular treatments may not have any significant effect in reducing it. Fadel (2015) observed the stimulating factors of mechano reflexes and metabo reflexes in increasing blood pressure. These nerve reflexes are found to increase ventricular contractility, heart rate and stroke volume, thus, enhancing cardiac output. Vasoconstriction in muscles helps to activate alpha-adrenergic receptors. It restricts blood flow in muscles and thus, balances the increase of blood pressure. Wright et al. (2021) observed that K_v7 channels excite neuronal activity in working muscles helping in the control of cardiovascular diseases.

Cardiac regulation is enhanced by autonomic nervous system in children, who performs exercises on a regular basis, which has been observed in Speer et al. (2019). It enhances their cardiac output. Sidhu et al. (2015) observed that in young adults, the mean arterial pressure fluctuates due to exercise pressor reflex. They also observed the increase in the leg vascular conductance of young adults. Peripheral hemodynamics is compromised in the elderly population.

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Effects Of The Exercise Pressor Reflex On Cardiovascular Responses

The differences and changes in cardiac output due to exercise are visible between young people and the elderly. Sidhu et al. (2015) noted that aging is a natural phenomenon, which does not change the effects of group III and IV afferent muscles that mainly contribute to regulate the mean arterial pressure. In case of young people, changes in cardiac output are noticed that, predominantly, helps in changing the mean arterial pressure, occurring due to exercise pressor reflex. But as the heart becomes weak in the elderly, the activation of peripheral vasomotor muscles helps to indicate the exercise pressor reflex in them. Another difference noticed is the role of group III and IV afferent muscles in increasing leg vascular conductance at the time of exercise in the younger generation while peripheral hemodynamics induced by exercise are compromised in the elderly population. The authors also stated that the cardiac output decreases with age that shows the effect of exercise on the peripheral and central hemodynamics. It shows the functional decline of group III and IV afferents due to fentanyl blockade in older individuals. This blockade occurs due to impaired autonomic regulation of heart. As these issues arise due to aging, so, Sardeli et al. (2017) investigated the cardiovascular risks like cardiac autonomic imbalance and excessive blood pressure elevation during resistance exercise by the elderly. They observed that high load and low volume in resistance exercise is a much safer practice than the low load one as it prevents blood pressure rise. Spranger et al. (2015) also observed the benefits of blood flow restriction training on the elderly and patients with compromised cardiac health, and helps prevent muscle mass loss.

Spranger et al. (2015) observed health benefits in patients due to blood flow restriction training. The effects of exercise pressure reflex in different diseases like diabetes, heart failure and hypertension have been observed by Grotle et al. (2020). The authors have also accounted for some other diseases like chronic kidney disease, peripheral artery disease, obesity, Parkinson’s disease and chronic pulmonary disease, that are found to be related to exercise pressor reflex. As a part of this study, the main focus is on the effects of exercise pressor reflex on hypertension.

Hypertension is an important concern across the world. Grotle et al. (2020) observed the increase in the health issue among 45% of the population in the US. It is often associated with deaths of individuals from stroke and heart diseases. The authors observed its increased incidence in elderly, who are engaged in these exercises. Mizuno, Mitchell and Smith (2016) explained the mechanism of blood pressure elevation during exercise. Altered mechano and metabo reflexes have been observed by the authors in hypertension. Mechano reflexes increase heart rate and blood pressure significantly while metabo reflexes keep the blood pressure unchanged.

Vianna and Fischer (2019) investigated the cause of rise of blood pressure during exercise. As per their findings, as there is an increase in the energy utilization rate, hence, to compensate the loss of energy delivery of oxygen to the muscles are increased, which in turn increases the cardiac output.

Exercise Pressor Reflex In Young And Elderly Populations

Smith et al. (2019) explained the effects of menopause, sex, and menstrual cycle on female exercise pressor reflex. Exercise pressure reflex may cause hormone fluctuation in both pre and post-menopausal women. They have also observed rise in estrogen levels due to exercise. Sardeli et al. (2017) observed high load exercise resistance in adult males.

Conclusion

Exercise pressor reflex has a vital role in increasing blood pressure in the individual as a response to extensive exercise. The two components- mechano and metabo reflexes act in response to the received stimuli. Mechano reflex is often found to exaggerate the exercise pressor reflex to such an extent that it might result into heart failure while metabo reflex while metabo reflex restricts blood flow in the muscles. People of every age group experience the effects of exercise but it affects the elderly population the most. As the heart activity is generally lowered with age, it weakens the heart. The activation of peripheral vasomotor muscles indicates the impact of exercise pressor reflex. It has both advantages and disadvantages on the health of the elderly. The benefits include muscle mass loss prevention while the negative impacts include the appearance of different diseases like different diseases like diabetes, heart failure and hypertension. As not many studies were found to explain its effects on gender-specific issues, hence, future research have an opportunity to shed light in this arena.

References

Fadel, P.J., 2015. Reflex control of the circulation during exercise. Scandinavian journal of medicine & science in sports, 25, pp.74-82.

Grotle, A.K., Macefield, V.G., Farquhar, W.B., O’Leary, D.S. and Stone, A.J., 2020. Recent advances in exercise pressor reflex function in health and disease. Autonomic Neuroscience, 228, p.102698.

Sardeli, A.V., do Carmo Santos, L., Ferreira, M.L.V., Gaspari, A.F., Rodrigues, B., Cavaglieri, C.R. and Chacon-Mikahil, M.P.T., 2017. Cardiovascular responses to different resistance exercise protocols in elderly. International journal of sports medicine, 38(12), pp.928-936.

Sidhu, S.K., Weavil, J.C., Venturelli, M., Rossman, M.J., Gmelch, B.S., Bledsoe, A.D., Richardson, R.S. and Amann, M., 2015. Aging alters muscle reflex control of autonomic cardiovascular responses to rhythmic contractions in humans. American Journal of Physiology-Heart and Circulatory Physiology, 309(9), pp.H1479-H1489.

Smith, J.R., Koepp, K.E., Berg, J.D., Akinsanya, J.G. and Olson, T.P., 2019. Influence of sex, menstrual cycle, and menopause status on the exercise pressor reflex. Medicine and science in sports and exercise, 51(5), p.874.

Speer, K.E., Naumovski, N., Semple, S. and McKune, A.J., 2019. Lifestyle Modification for Enhancing Autonomic Cardiac Regulation in Children: The Role of Exercise. Children, 6(11), p.127.

Spranger, M.D., Krishnan, A.C., Levy, P.D., O’Leary, D.S. and Smith, S.A., 2015. Blood flow restriction training and the exercise pressor reflex: a call for concern. American Journal of Physiology-Heart and Circulatory Physiology, 309(9), pp.H1440-H1452.

Vianna, L.C. and Fisher, J.P., 2019. Reflex control of the cardiovascular system during exercise in disease. Current Opinion in Physiology, 10, pp.110-117.

Wan, H.Y., Weavil, J.C., Thurston, T.S., Georgescu, V.P., Hureau, T.J., Bledsoe, A.D., Buys, M.J., Jessop, J.E., Richardson, R.S. and Amann, M., 2020. The exercise pressor reflex and chemoreflex interaction: cardiovascular implications for the exercising human. The Journal of physiology, 598(12), pp.2311-2321.  Components Of The Exercise Pressor Reflex Example Paper