The Karvonen formula is one of the bests that can be used to define your heart rate zones and anaerobic threshold. It is based on the heart rate reserve , so it takes into account both your resting heart rate and maximum heart rate. Therefore it gives a much better result than the formulas that use only the maximum heart rate.
During long-lasting activities you will lose water and some important electrolytes — salts and minerals — through sweat, and burn a lot of calories . Therefore it is important to refuel during and after such activities. This drink will help you to hydrate and to replenish electrolytes.