Fuel according to time and not distance! What’s important to understand is that even though you may be burning 500+ calories/hour, your body physiologically can only process 200-300 calories per hour. So, in general, we recommend starting off with 200-300 calories/24oz (c.700ml) of water/hour for 2+ hour workouts, and 100-200 calories/24oz (c.700ml) of water/hour for activities less than 2 hours. Listen to your body. If you are feeling hungry dial up the amount of calories, if feeling overly satiated/full, dial it back. The right amount may also vary based on the conditions (think temperature and humidity) and length and your intensity (how long, how hard, how far). When it’s hotter than your usual training temperature, keep the same calorie rate per hour, but increase water to thirst.