Effects of aging on abdominal muscle reflexes during exercise

Anatomical and functional changes of the cardiovascular system during healthy aging

As we age in good health, the cardiovascular system undergoes many anatomical and functional changes. Specifically, aging is associated with changes in myocardial contractility, impaired cardiac autonomic regulation due to adrenergic desensitization, vascular dysfunction, and changes in barometric reflexes. in blood. It is possible, however, that some of these alterations are in fact acceptable secondary adaptations that confer optimal autonomically controlled cardiovascular responses to these basic physiological changes in humans. the elderly (Sprranger et al., 2015). Age-related changes in this system may play an important role in reducing the cardiovascular response to physical activity in older adults. Indeed, the energizing response to exercise may be diminished in the elderly, according to a small number of studies that include manual exercise as well as post-exercise circulatory congestion. The following essay describes the effects of aging on the abdominal reflexes.

Muscle contraction is triggered by activating receptors that respond to mechanical strain or even to metabolic byproducts produced during skeletal muscle training, as it is aptly called. “Supercharged response to exercise”. . The stimulation of these receptors leads to the generation of somatosensory signals, which are then transmitted to the central nervous system by afferent fibers of groups III and IV (mainly sensitive to mechanically) and unmyelinated group IV (mostly metabolically sensitive) (Stone & Kaufman, 2015). Heart rate as well as blood pressure increase when afferent muscle fibers are activated during contraction, and this is due to increased sympathetic nerve activity, which is the main cause. This reflex has been the subject of much research over the past 70 years and has contributed significantly to our knowledge of the mediation of the basic cyclic adaptations that occur during exercise. . More attention has been paid to this reflex in recent years because of its potential association with an excessive cardiovascular response to exercise in the diagnosis of heart failure and hypertension (Smith et al. events, 2019). It has been suggested that overactivity of the pressor reflex during exercise is associated with reduced exercise tolerance as well as an increased risk of serious cardiac events as well as stroke at the time of exercise. exercise scores in both pathological conditions.

Although vascular conductivity can increase fivefold during exercise, brain input from skeletal muscle response keeps blood pressure steady or increases during activity. In both electrically induced and voluntary activities, the exercise pressure reflex is represented by identical heart rate and blood pressure responses. Studies using drugs that inhibit afferent neurons of the muscles of the lower extremities have shown an association of hypertensive muscle response to exercise in maintaining tight cardiovascular control. during dynamic exercise (Grotle, et al., 2020). When exercise is performed with a decrease in nerve input, these trials demonstrate that the increase in blood pressure and cardiac output is impaired.

Additional research has shown that electrically induced exercise with paralyzing epidurals, as well as equivalent induced activity in paralyzed patients, has no effect on blood pressure (BP) (Fadel , 2015). Furthermore, when electrical exercise is performed in quadriplegic patients, blood pressure decreases accordingly. Blood pressure does not rise during activity with a paralyzed leg, despite the fact that electrical muscle stimulation increases lactate production and decreases muscle glycogen levels. Thus, pressure reflex exercise stimulates sympathetic activity and maintains perfusion pressure by restricting blood flow to the abdomen. However, due to the reflex “reset” the modulation of the arterial pressure receptor on blood vessel conductivity, blood flow to the skin, brain, as well as muscles can also be affected during exercise. . Blood pressure (BP) is the most closely adjusted cardiovascular variable during exercise.

Exercise Pressor Response And Its Role In Maintaining Cardiovascular Control During Exercise

In a study conducted by Troy A. et al., in 2003, scientists investigated the effects of aging on people’s abdominal muscle reflexes during exercise, which they found to be positive pole. It is unclear whether aging affects this response, despite the fact that it is a key determinant in the regulation of exercise currents. The mismatch between muscular effort and blood flow causes the reflex to be activated. The reflex is thus activated according to a pattern in which the amount of work performed remains constant while the external impedance to the muscle current increases. (Nystoriak and Bhatnagar, 2018). We wanted to see whether age affects the blood pressure response to reflex engagement, whether sympathetic nervous system responses to reflex engagement differ in older and older adults. young or not. The results of this study support the hypothesis that muscle reflexes become less effective with age.

Due to physical activity, the sympathetic nervous system is engaged. This helps redistribute blood flow to activate muscles and prevent blood pressure (BP) from falling too low. Sympathetic activation is mediated by two brain systems: the central command system, which includes a predictive mechanism, and a muscular reflex known as the exercise pressure reflex. This is needed to trigger a muscle response as the fine afferent fibers in the contracting muscle are physically and metabolically responsive increasing overall firing. In forearm activity, muscle reflexes are activated when muscles become fatigued and when there is a mismatch between blood supply and energy needs.

The present study looked at the effects of aging on the abdominal muscle reflexes during exercise in humans, and the results were promising. It is unclear whether aging affects this response, despite the fact that it is an important determinant in the control of exercise flow. The mismatch between muscular effort and blood flow causes the reflex to be activated. For this reason, to trigger the reflex, a model was used in which the level of work was kept constant while the amount of external resistance to muscle flow gradually increased (Mcleod, Stokes & Phillips). They wanted to see if age affects blood pressure responses to reflex engagement, whether sympathetic nervous system responses to reflex engagement differ in young and old people. Are not. The results of this study support the hypothesis that muscle reflexes become less effective with age.

Researchers in another paper investigated the effects of aging on the role of group III/IV afferent muscle reflex-mediated exercise on cardiovascular response at the time of vigorous exercise active, which is a single-leg knee straightener that uses fentanyl in the shell to temporarily weaken the afferent muscle. . feedback at the time of the dynamic one-leg knee extension exercise. In the absence of adverse effects on the cardiovascular system at rest, fentanyl blockade reduces both cardiac output and quality of life during exercise in young adults, but in older adults, the reduction in cardiac output significantly less drug-induced cardiac arrest without affecting QL (Chrysostomou, et al., 2014). LVC and SVC in the elderly increased after fentanyl blockade, but decreased in the younger population. The contribution to the overall blood pressure response to exercise in groups III/IV remained age-matched, although significant age-related changes were observed. On the other hand, feedback-related afferent systems that contribute to the MAP response to exercise appear to be affected by age.

Significance Of Exercise Pressor Reflex In Heart Failure And Hypertension

With respect to the barometric reflex on exertion, while cardiac output appears to account for most of the Class III/IV-MAP-mediated response in young adults, neurofeedback to the heart declines with age, similarly Thus, the SVC change becomes intermediately dominant. Exercise stress reflexes in the elderly. It should be noted that at the peripheral hemodynamic level, while group III/IV- mediated feedback clearly contributes to the promotion of LVC during exercise in young adults (Chrysostomou, et al., 2014). ) then these afferent factors seem to be responsible for the decrease in obsolete LVC. Despite the fact that the present study cannot rule out the possibility of a sex-related change, this finding may be useful in explaining the restricted peripheral vasodilatation associated with exercise. to aging.

Conclusion

To summarize what has been said above, more than seven decades have been devoted to the study of “response to urgent exercise”. Increased exercise barometric reflex has been postulated to be associated with lower exercise tolerance as well as an increased risk of serious cardiac events and stroke at the time of exercise in patients. heart failure and high blood pressure, respectively. The compression reflex of the exercise is an important factor in controlling the exercise flow during activity. Although this is one of the most tightly controlled cardiovascular variables during exercise – and can be influenced by it as well as age – little is known about the effects of aging on this reaction. Blocking fentanyl reduces cardiac output and quality of life (QL) in young adults exercising at high intensity. In the elderly, drug-induced reductions in cardiac output are significantly less severe and do not affect quality of life. Due to fentanyl blockade, the LVC and SVC of the older population increased, but they decreased in the younger population.

References

Chrysostomou, V., Kezic, J. M., Trounce, I. A., & Crowston, J. G. (2014). Forced exercise protects the aged optic nerve against intraocular pressure injury. Neurobiology of Aging, 35(7), 1722-1725.

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

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

Mcleod, J. C., Stokes, T., & Phillips, S. M. (2019). Resistance exercise training as a primary countermeasure to age-related chronic disease. Frontiers in Physiology, 645.

Nystoriak, M. A., & Bhatnagar, A. (2018). Cardiovascular effects and benefits of exercise. Frontiers in cardiovascular medicine, 135.

Smith, J. R., Koepp, K. E., Berg, J. D., Akinsanya, J. G., & 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), 874.

Spranger, M. D., Krishnan, A. C., Levy, P. D., O’Leary, D. S., & 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), H1440-H1452.

Stone, A. J., & Kaufman, M. P. (2015). The exercise pressor reflex and peripheral artery disease. Autonomic Neuroscience, 188, 69-73.