Diastolic blood pressure rise during isometric exercise

Dear Ask The Doctor:  I am a 20 year old male with an unremarkable medical history who intensely exercises my upper body four times per week. I am generally in excellent physical condition, with a resting heart rate of 60BPM, and blood pressure in the vicinity of 120/80. Normally when I am at peak intensity of exercise, my pressure is around 140/65 with a heart rate of 150BPM. Seeing as my diastolic pressure normally drops when exercising, today I was quite perplexed when it rose. This occurred when I decided to do some bicycling, as I do not normally train my legs and wanted to change that. After 20 minutes of cycling at a moderate to lightly intense rate, my blood pressure was 178/99, with a heart rate of 140. The diastolic rise alarmed me, so I stopped. My question is thus: Can elevated diastolic pressure in this case be attributed to the fact that I was exercising untrained muscles, which would have underdeveloped vasculature compared to my normally trained muscles, resulting in suboptimal vasodilation and a general lack of capillaries/other vessels to distribute the blood flow? Thanks for any insight you can give.
 

Dear Patient:  Cardiovascular changes during isometric exercise (such as resistance cycling, resistance or weight training) differ from those during dynamic exercise. Static exercise causes compression of the blood vessels in the contracting muscles, leading to a reduction in the blood flow in them. Therefore, total peripheral resistance, which normally falls during dynamic exercise, does not fall and may, in fact, increase, especially if several large groups of muscles are involved in the exercise. Because the total peripheral resistance does not decrease, the increase in heart rate and cardiac output is less and an increase in the systolic, diastolic, and mean arterial pressure is more compared with those seen with dynamic exercise. Therefore that is why your diastolic pressure rose significantly in comparison to your normal blood pressure measurements.

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