Greetings.

I'm 63 years old and parallel to the topic I am about to expand upon, am trying to self-diagnose what are still mysteries in my overall health in the past two years. On our favorite two-wheel instrument, my strength dropped suddenly last year in May by about 10% - and never recovered. Without a better theory, I chalked that up to an aging burst. However, throughout, my average heart rate was always in the mid to upper 140s, and my maximum around 166 or so....until.

Suddenly, about a month ago, I lost ten beats, both on my average and the maximum. I assure you this is not over-training (my regimen year-to-year is almost robotic) and also not a burst in fitness (or I'd not have maintained the power and speed loss).

Can anyone think of any medical reason for this heart rate loss? Thanks