We all love Grand Cayman’s climate, but exercising in the heat brings additional challenges, not least of which is hydration. Many of us struggle to maintain optimum hydration even while sedentary. Adding exercise into the mix brings added complications.
Preparation is key and we should try to start our workout optimally hydrated by including hydration in our daily dietary considerations. Consuming 0.5 ounce to 1 ounce of water per pound of body weight per day is an often quoted ideal, but the right amount for us becomes evident from monitoring our hydration.
If we’re dehydrated, our urine is dark coloured and smelly. Completely clear urine can be a sign of over-hydration. The colour of our urine should be slightly yellow.
If we start our workout hydrated, then staying hydrated during short workouts can rely on water alone, but for longer 60-minute-plus efforts and for post-workout rehydration, additional electrolytes are required. The body’s need to be refuelled also begins after 45–60 minutes, so both energy and hydration can be efficiently boosted using energy drinks that include electrolytes. Failure to replenish our electrolytes can lead to reduced sodium levels and hyponatremia.
It’s not possible to stay completely hydrated during our workout as the body cannot absorb fluid as fast as we sweat it out, so we will get dehydrated. The ability to absorb fluid into the bloodstream varies by individual from about 0.6 litres to 1.2 litres per hour and will vary depending on the intensity and type of workout. Sweat rates during exercise can also vary widely from 1 litre to 3 litres per hour.
Our goal is to stay hydrated enough to avoid reduced performance without detracting from our efforts by stopping too often to drink or urinate. While the amount of dehydration that has to occur before performance is reduced is not globally agreed, it will vary between individuals and at some point dehydration will become a problem for us and needs to be mitigated. A good initial strategy might be to drink when thirsty, but stay within the 0.6 litre- to 1.2-litre-per-hour range.
To assess the success of our hydration strategy and determine post-workout rehydration needs, a useful guide can be to measure our weight before and after a workout. The difference won’t be due to fat loss, but will approximately reflect our fluid deficit. A hard effort in the heat can lead to a 3 per cent loss in body weight; running a 26.2-mile marathon can result in a 5 per cent weight loss. Given a litre of water weighs about 1 Kg (a pint weighs about a pound) it’s easy to calculate our fluid deficit. We will need to drink more than this amount to rehydrate as not all consumed fluid will be absorbed.
If we can reduce this deficit for subsequent workouts by consuming more fluid and electrolytes without additional toilet stops, then we have improved our hydration strategy and most likely our performance, too.
Tony Watts is a 50-something-year-old fitness fan who teaches cardiovascular and weight/resistance training classes at gyms on Grand Cayman.