By "low 40s" I mean 42-45 when I first wake up in the morning. I wore a heart rate monitor at work a few weeks ago, and my HR sitting at my desk can drop to 52. To what do I attribute it? Hours of hard work at the other end of the heart rate scale. Spend enough time at 90% of your max, and the ticker gets really strong! As much as I like cycling, I hate doing it in snow and ice, so in the winter I do interval training in a pool. That's good exercise too, but not everyone has access to a pool.