Hello. Thank you for asking on HCM. I understand your concern. Normal heart rate standardized for the population worldwide is 60-100 beats per minute. During moderate to strenuous activity heart rate tends to go significantly high, because of the heart working hard to adapt and supply the body properly in case of physical stress. As such, there is a formula dedicated to this. During physical activity, heart rate goes up to 220 - age. In your case, up to 158 beats per minute. My opinion is that there is nothing to worry about, unless this increase is heart rate is also accompanied with irregularity of the heartbeats. You should also remember that, during the day there are a lot of diurnal and nocturnal hormonal level changes in the human organism, which affect, directly or indirectly, the vagal and sympathetic tone, which are directly linked to the changes of heart rate. I hope I was thorough in my answer. Take care. Best regards.