Darren Jones also had a question about heart rates:As well as using the Concept 2, my wife and I ride bicycles as part of cross-training, and do so wearing heart rate monitors. When going up a decent sized hill, she (28 years old, not overweight, but not as fit as she would like) frequently has a heart rate of more than 100% of maximum rate as defined by the usual 220 minus age equation. This also happens to us both when doing a 2000m test. What recommendations could you make regarding sustaining very high output levels for non-professional sportspeople?Tel says: A measure of your physical condition is your ability to do prolonged work close to your max heart rate. As a result of training, anaerobic threshold is pushed up to around 85% of heart rate max. The heart also benefits and increases the amount of blood it is able to pump around each beat. This means that for a given task, as you get fitter your heart rate will come down or alternately you will be able to do more work at a given heart rate. Unless you have some heart or circulatory problems I do not believe there is any danger in going flat out. Training at the higher heart rate will have the most impact on your cardio-vascular system with low heart rate exercise improving muscular efficiency. It's all in the Concept 2 training book that you can get off our web-site.