Hydration for the Next big Race

Nutrition and hydration has a crucial role to play when it comes to training for the next big race.

How Hydrated are you?? . Just as there are many ways and means to take in fluids (water, sports drinks, and water-containing foods all come to mind), an easy and cheap way to check approximate hydration status from the comfort of your own bathroom. By simply noting the color and volume of your urine you can gauge whether you need to drink more (or maybe less). Dark-colored urine of a relatively small volume is an indication of dehydration and should signal you to drink more fluids throughout the day or during your run.

2. Hydrate before heading out. In general, consider following this recommendation adapted from The American College of Sports Medicine’s Position Stands. Exercise and Fluid Replacement: Drink approximately 30ml per every 5kg of body weight four hours before running, and if profuse sweating is expected, drink ~17ml per every 5kg of body weight 2 hours before a run. Give yourself time to use the bathroom before you head out.

3. What is Your game plan. While some experts recommend you stay hydrated by simply drinking when thirsty, others suggest you develop a customized plan by performing a sweat test. To stay better hydrated during long, hot runs (or even windy, frigid runs, for that matter), you need to perform a sweat test. Weighing yourself before and after exercise is the most effective way to gauge your fluid needs. Any weight loss corresponds with fluid loss, so try to drink enough to replenish that weight. (Weight gain could mean you are drinking more than you need.)

4. Recognize your losses. Electrolytes are lost both in sweat and in urine. Some athletes lose a lot of electrolytes while others don’t, and there’s wide range of the amount lost. As you can see in the table below, sodium and chloride are lost in larger amounts than potassium, magnesium, and calcium, as well. The values listed represent the amount of electrolytes contained in a liter of sweat. Keep in mind that individual athletes lose varying amounts of sweat, so use the table below as a ballpark reference. sodium-potassium balance can be compensated by Intake of Coconut water in the first week of the race.

Table adapted from Sports Nutrition: A Practice Manual for Professionals, 5th Edition.

5. If you can replace sweat losses during the run, research shows that you’ll better optimize cardiovascular, thermo regulatory and performance responses. Use your sweat test results to determine how much fluid you need each hour. If you’re going for a leisurely run or a run that lasts less than an hour, you can stay hydrated with water every few kilometers. If you’re a salty sweater, cramp-prone or going longer than an hour, you might want try adding some electrolytes to your water. There are a few options out on the market, and a select few are listed in the table below. If you’re going for a long and taxing run, you might want to opt for a carbohydrate-containing sports drink rather than water and electrolytes alone.

Not all drinks take the same amount of time to reach your bladder. This fact, a team of researchers write in a recent American Journal of Clinical Nutrition article, “is of real clinical and practical benefit in situations in which free access to fluids is limited or when frequent breaks for urination are not desirable.”

As it turns out, there are a lot of factors that affect how quickly you pee out a given drink. For example, drinks with lots of calories or electrolytes tend to be retained in the body for longer, while diuretics like caffeine and alcohol speed things along. How much you drink at a time also has an influence. And despite all the folk-wisdom out there, there’s very little actual data comparing different drinks.

To address this gap, researchers led by the University of Loughborough’s Ron Maughan, along with colleagues from Bangor University and the University of Stirling, UK, recruited 72 subjects to test 13 different drinks (each subject tested water plus three other drinks). At each testing session, the subjects drank a liter of the chosen beverage, then collected all their urine for the next four hours.

The result is a “beverage hydration index” that compares how much of the drink was retained after two hours compared to a liter of water. (They used two hours because most of the urine had been passed by then, and it represents a more realistic time interval between drinks than four hours.)

So, without further ado, here’s the data:

A higher bar indicates more fluid retained. The dashed line represents twice the coefficient of variation away from water, meaning you can be relatively confident it’s a real effect above that line. ORS is retained well followed by Skimmed milk, Full fat milk and orange juice.

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