2) it is ideal to start quality training runs well-hydrated. This is challenging for very early morning runs because you don’t necessarily want to guzzle a gallon of water before the run. In fact, that’s not recommended at all. Try to drink in the range of 10-16 oz fluid when you wake up. As the outside temperatures begin to increase with the approaching summer, it is important to drink fluid during your runs over 75 mins. There is no exact formula that works for everyone, so pay attention to thirst and honor it. However, be aware that the stomach cannot efficiently absorb over 28 oz of fluid per hour. Sodium can help with water absorption and a touch of carbohydrate can help with sodium absorption. If you’re getting a sloshy stomach often, there likely is an absorption issue that is related to overall amount of fluid you are consuming, type of electrolyte you are consuming, or timing of intake.
3) It is possible you are under-consuming or overdoing it with electrolytes (specifically sodium, which is the primary electrolyte we lose in our sweat) and plain water consumption. There is a potential performance effect. How much fluid you need and sodium supplementation you need depends on your personal sweat rate (which is straightforward to measure yourself throughout the training season) and your sweat sodium concentration. The latter can be measured with testing equipment and is a non-exercise test. (Ewen, Ellen Moeller did this with me if you want to ask her about it - if she’s comfortable talking about the test). The physiology of everyone’s sweat glands is different and as such, some of us are more ‘salty’ sweaters than others. Combined with a heavy sweat rate (we recognize those runners by the fact they are dripping with sweat and clothes are drenched!), this can mean a need for a specific hydration and electrolyte strategy.