------------------------ The Karvonen formula is the gold standard for training zones. It is based on your Reserve Heart Rate, the difference between your maximum HR and your Rest HR, rather than only the max heart rate. 50% to 60%: Recovery and weight loss zone. 60% to 70%: The heart starts to benefit from the exercise. Slow and long distance exercise. Fat is the primary fuel and therefore good zone for weight loss. 70% to 80%: Aerobic zone - This is the optimal zone to workout in to increase your cardio-respitory capacity or the bodies ability to transport oxygenated blood to the muscle cells and carbon dioxide away from the cells. 80% to 90%: Cross over from aerobic training to anaerobic. Training in this zone will improve performance and dealing with Lactic acid. Training in this zone is felt as hard. 90% to 100%: Red Line Zone - You will only be able to train in this zone for short periods of time. You should not train at this level unless you are very fit. In this zone lactic ...