By: Christopher D. Jensen, PhD, MPH, RD
Nutrition & Epidemiology Researcher

Both dehydration and overhydration can have a negative impact on workouts and adversely affect the health of your clients. How can you as a personal trainer help your charges hydrate properly before, during, and after workouts? Here are 10 useful suggestions to implement when working with your clientele:

• Encourage starting workouts well hydrated.If a client is carrying a fluid deficit from an earlier workout, chances are good that he or she will become dehydrated at their next exercise session. You can help prevent this by advising clients to get into the habit of consuming 14–20 fl oz (400–600 ml) of water 2–3 hours before exercise. Suggest that they carry a water bottle or sports bottle to class, on errands, at home, or on the job, and that they take sips regularly.
• Teach how to monitor hydration status. By monitoring urine volume and color before working out, your clients can judge for themselves whether they’re sufficiently hydrated. Large amounts of clear or light-yellow urine equate to being well hydrated. Small volumes of dark urine suggest more fluids are needed before heading to the gym.
• Explain the hydration zone. Let your clients know that when it comes to hydrating during exercise, the goal is to avoid gaining weight (a sign that they’ve consumed too much fluid) and avoid losing more than 2% of their pre-exercise body weight (the level of fluid loss beyond which athletic performance is undermined). This is the hydration zone, where individuals perform at their best and avoid the adverse health effects of dehydration and overhydration. So a client whose typical pre-exercise weight is 150 lbs (68 kg) should be hydrating during exercise at a rate where body weight stays between a high of 150 lbs (68 kg) and a low of 147 lbs (about 67 kg) (cont’d) Sweat Rate calculator.