Circulatory responses of both heart rate and blood pressure shift during modality, intensity, and frequency of the exercise being performed due to two major physiological reasons. The first reason is in regards to skeletal muscle blood flow. The metabolic demands of the muscles being contracted during exercise must be matched by blood flow (Joyner & Casey, 2015). The second regulating factor is systemic control of arterial pressure. The pressure needs to adequately perfuse to all of the other organs in the body (Joyner & Casey, 2015).
Transition from Rest to Exercise
At the onset of training, oxygen consumption increases triggering an increase in heart rate, stroke volume and cardiac output. As oxygen consumption increases , oxygen from the hemoglobin in the flowing blood is extracted at enhanced rate as an immediate way to increase supply (Sarelius & Pohl 2011).
In order for the a steady state plateau to occur in heart rate, stroke volume and cardiac output, work rate must remain constant and below that individual’s lactate threshold (Powers & Howley, 2015). The combination of vagal withdrawal and increased sympathetic nerve activity to the heart are responsible for the increase in heart rate (Joyner & Casey, 2015).
Emotional Response
Both heart rate and blood pressure can also be affected by an individual’s emotional state via increased sympathetic responses. This increased sympathetic response does not however seem to affect peak heart rate and blood pressures during exercise, only pre exercise levels (Powers & Howley, 2015).
Incremental Exercise
In the case of incremental climbing exercise bouts, as oxygen uptake increases, so do both heart rate and cardiac output in direct proportion. Another response happens in the muscles in which increased blood flow brings more oxygen to allow for ATP synthesis (Powers & Howley, 2015). Systolic pressure increases during exercise, which causes an increase in arterial blood pressure. Double product occurs because of the increased work the heart undergoes heart (Powers & Howley, 2015). Double product is a great measurement for prescribing exercise protocols for those with artery blocks (Powers & Howley, 2015).
Intermittent Exercise
The greatest level of variability is seen interval style training pending a number of variables which all affect heart rate and blood pressure recoverability (Powers & Howley, 2015). Recovery of each is highly dependent upon the individual’s level of fitness in addition to the duration and intensity of the activity and duration and intensity of the recovery period. In most instances a full recovery can be made if variables such as temperature and humidity are cool and low (Powers & Howley, 2015).
Prolonged Exercise
In contrast with prolonged training, cardiac output, stroke volume, and heart can all be maintained at one constant level, given that the exercise performed is done so at a constant work rate (Powers & Howley, 2015). The longer the duration of this style of exercise the lower stroke volume levels become. Heart rate, however, begins to increase with greater frequency, a process known as the cardiovascular drift. The cardiovascular drift occurs due to a reduction in plasma volume caused by elevated body temperatures on dehydration (Powers & Howley, 2015). Stroke volume is reduced due to reduced venous return to the heart caused by reductions in blood plasma. This reduction in stroke volume and elevation in heart rate occurs at greater level when the individual exercising is exposed to hot and humid conditions (Powers & Howley, 2015).
Arm vs leg training
Depending on the muscle groups being utilized during the activity, variances can be seen between upper and lower extremity in regards to heart rate and blood pressure, increased sympathetic output occurs with the upper extremity use causing the greatest increases at a given oxygen uptake (Powers & Howley, 2015). Inactivated muscle groups have increased vasoconstriction, which causes and increase in blood pressure (Powers & Howley, 2015).
Recovery from exercise
At the completion of the exercise session, pending the duration and intensity level, heart rate, stroke volume and cardiac volume all gradually return to baseline (Powers & Howley, 2015). Highly conditioned athletes can experience rapid recovery in those three aforementioned areas due to their heart rates not climbing as high as untrained individuals (Powers & Howley, 2015). This adaptation is seen among trained individuals as their cardiopulmonary systems are much more adapted to training modalities and varying intensity levels. It should be noted that the temperature at which the individual is training at will affect heart rate recovery following exercise. Individuals exposed to elevated heat temperatures or humidity will see a delayed drop to resting levels in their heart rate (Powers & Howley, 2015).
Sources:
Joyner, M.J., & Casey, D.P. (2015). Regulation of increased blood flow (hyperemia) to muscles during exercise: A hierarchy of competing physiological needs. Physiological Reviews, 95(2), 549-601. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4551211/
Powers, S.K., & Howley, E.T. (2015). Chapter nine circulatory responses to exercise. Exercise physiology: Theory and application to fitness and performance (9th ed.) (pp. 185-212). New York, NY: McGraw-Hill Education.
Sarelius, I., & Pohl, U. (2011). Control of muscle blood flow during exercise: Local factors and integrative mechanisms. Acta Physiol, 199(4), 349-365. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157959/
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