What conditions can cause exercise intolerance?

Question

Hello doctor,

I am a 47-year-old female weighing 147 pounds. My heart rate is 52 beats per minute when I wake up in the morning. During the day, my resting heart rate ranges from 75 to 82 beats per minute. After a 5 km walk (which takes me 37 minutes), my heart rate reaches 195 to 200 beats per minute, and during high-intensity exercise, it can go as high as 205 beats per minute. I experience delayed onset muscle soreness two to three days after a significant exercise session. I often feel fatigued and suffer from lightheadedness and tremors after exercising, which I find to be hard work. I have anemia and take ferrous fumarate (with ferritin levels between 30 and 35 ng/mL), but all other blood work is normal. A cardiogram did not reveal any issues. Are there any specific dietary aspects I should pay attention to? What is your opinion on my exercise and heart rate zones? Are there any specific tests I should request?

Please advise.

Answer 1

Hello,

Welcome to icliniq.com.

The overall picture indicates exercise intolerance, as you should not have a heart rate exceeding 200 beats per minute during exercise. The primary cause here appears to be anemia, which you need to address before starting any exercise program. Additionally, the muscle soreness you are experiencing may be due to rhabdomyolysis, a condition characterized by muscle breakdown resulting from very intense exercise. Along with an anemia workup, I recommend a thyroid profile, as thyroid issues can also lead to myopathy (muscle disease).

I hope this helps you.

Thank you.