Most athletes will admit that from time to time it is hard to monitor and maintain a specific intensity in their training. Many tools and technologies have been harnessed to gauge the level of intensity that the athlete trains at. Some of these tools or physiological metrics are more scientific than others. Some of these tools require very expensive machinery and laboratory tests. A metric tool that I have found to be very helpful in my own training, and a useful tool in the training of the athletes I coach is heart rate zone training.
Mark Allen, a several time winner of the Ironman Championship in Kona, Hawaii is an evangelist for the heart rate training. He has authored numerous articles and books about the subject area of heart rate and training zones, and could be considered one of the foremost experts in this area. Most of the methodology that I use when designing a training program is the very same philosophy that Allen teaches in his own coaching and writing. I found an article that was written pretty recently by Mark, discussing the topic of heart rate zone training. http://www.duathlon.com/articles/1460At
Let me put a disclaimer on this article, in that heart rate can be variable considering ones age, health condition, level of athleticism, and wellness (sick or ill). Heart rate can also vary by sex, week of menstral cycle, weather conditions, and other implications. Heart rate monitoring must be conducted within the framework of safe medical clearance as well as consideration for any extenuating circumstances. I hope you enjoy this article. Please feel free to contact me with questions or comments.
All the best,