Do Sweat the Small Stuff


My dad taught me not to sweat the small stuff – a key to managing anxiety and stress in life. It’s worked for him as he’s still a practicing family doctor at age 82 and as sharp as a tack with few health issues. But what about real sweating – losing fluids in sport! What impact does it have on sports performance? Here is a summary of a very recent review published in the highly-credentialed Nutrition Reviews journal highlighting that we shouldn’t lose anymore than 2-3% of our body weight in fluids before we decrease performance. Moreover, this review throws doubt over many of the long-held beliefs regarding fluid replacement needs in athletes.

Historically, research suggested suggested that fluid loss of anymore than 2% loss of body weight impairs endurance performance under any conditions and that athletes should always drink before feeling thirsty to maximize endurance performance. However, there is recent evidence suggesting that cycling time trial performance is not affected by up to 4% of body weight loss and that drinking when thirsty maximizes endurance performance. Moreover, a 2011 study published in the British Journal of Sports Medicine  showed that the marathon times of 643 runners were inversely correlated to their end-of marathon body weight loss. That is, the greater their body weight loss, the faster they ran!

The Research

This paper rightly questions how well-published and strongly-adghered to fluid replacement guidelines are often based on laboratory-based (vs real world) studies often using fixed power output time trials (vs the real world where pacing and changes of speed are normal) and often using testing methods with poor reliability such as time to exhaustion at a set speed. The review highlights five recent studies that simulate real-world racing conditions. None of these studies showed any difference in performance between being dehydrated less than 2% or greater than 2% in body weight. In fact a couple of studies have suggested that the greater the body weight loss, the better the endurance performance. This has been shown in marathon runners, Ironman triathletes, and 24-hr ultramarathoners. The review also highlighted that Haile Gebrselassie won the 2009 Dubai marathon after a body weight loss of 9.8%. While this information shouldn’t be interpreted as supporting becoming dehydrated to enhance endurance performance, it does question the current guidelines that maintaining body weight loss to no greater than 2% of body weight is critical to endurance performance.

The New Guidelines?

This peer-reviewed and well-researched review provides guidelines to help athletes, coaches and sport health practitioners with guidelines for developing safe hydration plans for endurance athletes. These include:

  1. Be well-hydrated before exercise: It’s been well-documnetd that many athletes start exercise dehydrated and that doing this decreases performance. In the last 2 hours before exercise, athletes should drink fluids when they feel the need but should be around 5-10 mL/kg body weight of sports drink or water. They should drink to the point of having two pees before competition and ensure that the pees are straw yellow or clear that indicates they are hydrated.
  2. Drink according to your thirst: no more, no less: This is an individual sensation but normally means a dry and sticky mouth and throat. Nerves and food intake can sometimes cause this as can very dry weather. Plan ahead and trial a hydration plan in training, ideally in conditions that replicate the conditions of the goal event.
  3. Limit fluid intake in events shorter than one hour: Research consistently shows that fluid intake has no bearing on performance in endurance events shorter than one hour. Gut upsets can occur in some people whan taking in fluids during high intensity endurance events typically shorter than 60  minutes.  As an option, consider mouth rinsing with 20-25 mL of sports drinks for 5-10 seconds every 8-10 minutes.  

Always try before you buy – more father advice! Practice the guidelines above for yourself before doing it in competition. Also remember that these are guidelines and that you as an individual neeed to determine, usually by trial and error, what works best for you.

There are some specific suggestions on hydrating as an older athlete that are discussed in Chapter 11 (Exercising in the heat and cold) of my book The Masters Athlete that is now available as a pdf or as separate chapter pdf’s. Check it out – it’s the most comprehensive book for older athletes that has ever been published.

Goulet, E. (2012). Dehydration and endurance performance in competitive athletes. Nutrition Reviews. 70(Supplement 2): S132-S136.