Hello! Welcome and thank you for asking on HCM! Regarding your concern, I would explain that it is normal to have an increased heart rate during physical activity, especially when you are not performing regularly physical activity and your body can be over-stressed by the physical exercise. The episodes of blackouts after going for runs are a little concerning. They could be related to a low blood pressure (orthostatic hypotension), low blood glucose, hyperventilation or cardiac arrhythmia. I recommend you to consult with your GP for a careful physical examination, a resting ECG, a chest X ray study and some blood lab tests : -complete blood count - thyroid hormone levels - blood electrolytes - kidney and liver function tests - fasting glucose. A treadmill test may be necessary to exclude possible cardiac arrythmia related to physical exercise. You should discuss with your doctor on the above mentioned issues. Hope to have been of help! Best regards! Dr. Iliri