The Exercise Pressor Reflex: Should We Be Concerned? Part 1

 

Demand is coming-Are you ready?

The Exercise Pressor Reflex: Should We Be Concerned? Part 1
Nicholas M. Licameli, PT,DPT

 

A barrier to the widespread implementation of BFR exercise, especially in the elderly and those with obesity (Dipla, 2012), diabetes (Grotle, 2019) as well as cardiovascular conditions such as hypertension (HTN) (Greaney, 2013), heart failure (HF) (Spranger, 2015), and peripheral artery disease (PAD) (Spranger, 2015), is the exaggerated cardiovascular response to exercise, specifically the exercise pressor reflex (EPR).  The EPR has two functional components: the muscle metaboreflex (reduction oxygen/blood flow to muscle tissue and the accumulation of metabolites) and the muscle mechanoreflex (mechanical distortion of group III afferents due to tissue compression during skeletal muscle contraction (Kaufman, 1984) in direct proportion to the intensity of the exercise (Adreani, 1997, Kaufman, 1983,  (Boushe, 2010, McCloskey, 1972, Mitchell, 1983).  Both components act to increase sympathetic nerve activation (SNA) during exercise.  

 

Along with central command and the arterial baroreflex, the EPR causes the autonomic cardiovascular response to exercise and subsequent increases in heart rate (HR), cardiac output (CO), cardiac contractility, and blood pressure in direct proportion to the intensity of the intensity of the exercise (Spranger, 2015).  In other words, the harder the exercise, the greater the response.  In a study of submaximal cycling, Osaki, et al showed increases in MAP, SBP, DBP, rate-pressure product, and total systemic peripheral resistance with higher exercise intensities (% VO2 max).

 

Now what????  Are there ways to modulate the EPR without sacrificing the effectiveness of something like BFR?  C’mon now…you didn’t actually think I was going to leave you empty handed and put the stake into BFR, did you?  

 

To limit the effects of the EPR, consider (1) avoiding exercises that require a strong valsalva maneuver, (2) selecting cuff pressures that are on the low end of the range of effectiveness and using intermittent BFR, (3) choosing dynamic over static exercises while avoiding failure, (4) and performing exercises that use small muscle groups rather than large muscle groups.  

 

Stay tuned for Part 2, where we will dive into each of these topics and more in greater detail!  See you then!

 

References

Adreani CM, Hill JM, Kaufman MP. Responses of group III and IV muscle afferents to dynamic exercise. J Appl Physiol 82: 1811–1817, 1997.

 

Boushel R. Muscle metaboreflex control of the circulation during exercise. Acta Physiol (Oxf) 199: 367–383, 2010.


 

Dipla K, Nassis GP, Vrabas IS. Blood pressure control at rest and during exercise in obese children and adults. J Obes. (2012) 2012:147385. doi: 10.1155/2012/147385.

 

Greaney JL, Matthews EL, Boggs ME, Edwards DG, Duncan RL, Farquhar WB. Exaggerated exercise pressor reflex in adults with moderately elevated systolic blood pressure: role of purinergic receptors. Am J Physiol Heart Circ Physiol. (2014) 306:H132–41. doi: 10.1152/ajpheart.00575.2013.

 

Grotle A-K, Stone AJ. Exaggerated exercise pressor reflex in type 2 diabetes: potential role of oxidative stress. Auton Neurosci. (2019) 222:102591. doi: 10.1016/j.autneu.2019.102591.

 

Kaufman MP, Longhurst JC, Rybicki KJ, Wallach JH, Mitchell JH. Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats. J Appl Physiol 55: 105–112, 1983.

 

McCloskey DL, Mitchell JH. Reflex cardiovascular and respiratory responses originating exercising muscle. J Physiol 224: 173–186, 1972. 

 

Mitchell JH, Kaufman MP, Iwamoto GA. The exercise pressor re- flex—its cardiovascular effects, afferent mechanisms, and central path- ways. Annu Rev Physiol 45: 229–242, 1983.

 

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 physiology309(9), H1440–H1452. https://doi.org/10.1152/ajpheart.00208.2015



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