I am a 26 year old male, non-smoker. My normal resting heart rate is between 42-50. I have lost 30 pounds through exercise over the past 6 months and I now weight what I should, 158 I am 5'9". My heart rate was still in that range six months ago though. My real question is, MAny afternoons I get uncontrollably tired, head nodding to the side, unable to keep it up. One day about a month ago, i decide to check my pulse during one of these episodes, it was 36, subsequent checks during these episodes confirmed that my heart rate drops to 35-40 range when I feel this tiredness. Being 26, and not a world class ahtlete, should I be concerned. My GP says I am too young to have a low heart rate effect my energy level, he did an EKG and it was normal. Any advice is much appreciated.