I recently wrote about the 2013 (EAH) and key points to consider when it comes to maintaining hydration status. Research that has been published in 2012, and 2013 has discussed the concept of drinking to thirst. The key point to keep in mind is how do people interpret the concept of “drinking to thirst?” It can be interpreted very differently. For this article, it means to drink when you are thirsty.
Waiting to drink until you feel the sensation of thirst assumes quite a few things: a) you will be alert enough to distinguish the sensation of thirst or differentiate the difference between thirst and hunger, and b) you have the luxury of having fluids available at the moment you are thirsty. My first point is specific to anyone racing a half or full ironman in hot conditions (e.g. Florida, Hawaii, Louisville) and has experienced heat so extreme they cannot think straight, their internal core temperature feels like lava from heat radiating off the pavement, and they border on nausea. During those conditions you have so many body parts sending feedback to your brain, that you aren’t sure if you are thirsty or not – but you know you must be because you haven’t stopped sweating for four hours! Training and preparing your fueling/hydration strategy in those conditions will help you manage the feeling of steam coming out of your ears, and will also help you determine how much fluid/carb you can take in and actually assimilate. So, we do recommend a timing strategy for hydration in triathlon which is also noted in this article in Nutrition Review. The article recognizes my first point of concern and notes, “In athletes whose thirst sensation is untrustworthy or when external factors such as psychological stress or repeated food intake may blunt thirst sensation, it is recommended to program fluid intake to maintain exercise-induced body weight loss around 2% to 3%.”
As a cyclist you can carry fluids on your bike and plan on where you can refill them to keep to a set schedule of fluid intake. Again, a set strategy (in addition to knowing your body) is recommended since often times we under estimate our sensation of thirst. On hot, dry days in Colorado with a slight breeze, it’s easy to not drink for a hour because you dont feel thirsty. Instead, you are paying attention to a headwind and don’t particularly feel thirsty. Most runners carry hand held water bottles with them when they go out for a ‘long run’ which allows them the luxury of having fluid available if they feel thirsty – and if they don’t, they don’t drink. Its simple.
While I was attending the American College of Sports Medicine (ACSM) Annual Meeting this past June, there were several abstracts posted on this topic as well. The posters represent graduate level research completed on runners who may run for two hours and not drink anything. However, the students I spoke to, generally did this based on their own personal desire not to drink and it may or may not have affected their performance. The mental aspect to running without drinking is an entirely other topic. Completing long runs without drinking may have a small role in your overall training plan if you are a marathon racer and need to put yourself under the physiologic strain comparable to what you might have in a race. However, when it comes to triathlon and the run is the last leg – a very long leg – after a day’s worth of sweat loss, you do not want to be playing games. Of course, you do want to listen to your body as best as you can; just refer to Macca’s account of his saving grace using Cola in the World Champs.
When it comes to performance decrements related to percentage of body weight loss, I generally don’t pay much attention to the 2-4% parameters because most athletes I work with, especially in the southeastern states, have sweat rates higher than 5% weight lost, which is always significant. You cant prevent weight loss from sweating, only minimize it.