I am currently training for a 24 hour mountain biking event in may. I will be on a 4 person team and will be riding approximately 6 hours during the event. I have done this event twice in the past and have done well. I am hoping to be more scientific in my training this year. I do most of my training on my road bike and use a HRM. I'm looking for tips on heart rate training or web sites/books that you recommend. Any help would be appreciated.