It’s marathon season, and one thing almost all runners worry about at some point during their training is the best way to hydrate during the race. It’s one thing to practice during long training runs, but things can feel completely different out on the course.
I recently caught up with Dr. Bob Murray, a marathon runner and the leader of POWERADE’S sports science program, to find out more about proper hydration, hyponatremia, and drinking water versus a sports drink.
Running Examiner: What is the best hydration tip you could give to marathon runners?
Dr. Murray: My advice to marathoners is simple: drink to minimize weight loss, but don’t over-drink. To become skilled at drinking enough while running, the easiest approach is to periodically weigh yourself before and after long training runs. If you’ve lost more than a couple pounds, you should increase your fluid intake the next time out. If you’ve gained weight, that’s a clear sign that you’ve consumed too much and need to cut back on future runs.
After weighing in and out a few times, most athletes develop a good sense of how much they need to drink to minimize weight loss.
Running Examiner: What are the most common hydration mistakes you see marathon runners making?
Dr Murray: Most marathoners don’t fully understand the performance benefits of staying well hydrated and so drink too little, finishing races dehydrated, sapping performance as a result. A few marathoners over-do hydration, drink too much, dilute their blood sodium levels, and become hyponatremic.
Running Examiner: There has been a lot written about hyponatremia over the past couple of years. How concerned do runners need to be about drinking too much during a marathon?
Dr. Murray: There’s really no need for marathoners to be concerned about hyponatremia, but there is a need to be aware of it. Drinking too much water has killed marathoners, six since 1993, one more reason why marathoners should drink to minimize weight loss, but avoid over-drinking.
Running Examiner: A recent study in the British Journal of Sports Medicine suggested that the fastest marathon runners actually drank less and get more dehydrated, with little negative impact. How does that fit into things?
Dr. Murray: That particular study showed that those who finished the marathon in under 3 hours were usually more dehydrated than those who finished in 4 hours or more. That’s not surprising since faster runners sweat more and, like most athletes, tend to under-drink during exercise, in part because running fast makes it difficult to drink.
Slower runners often walk through aid stations, are on the course longer, sweat less, and so dehydrate less. The authors of this study believe that because faster marathoners are often dehydrated, that dehydration does not impair performance and in fact may help performance. I believe that if faster marathoners dehydrated less, they’d be even faster marathoners.
This year in North America there are over 160 marathon races between September and year’s end, meaning hundreds of thousands of marathon contestants. Very few of those runners will become hyponatremic and even fewer will require medical attention. That said, hyponatremia can be deadly, so it’s a good for marathoners to recognize that over-drinking is unnecessary and unhealthy.
Running Examiner: Most marathon aid stations offer both water and a sports drink like Powerade. Should runners be switching it up at each water stop, or just taking in the sports drink?
Dr. Murray: Any marathoner interested in getting the most out of his or her body should favor a good sports drink over plain water. For example, Powerade ION4 provides benefits that plain water can’t match. Powerade ION4 is mostly water, but its carbohydrates and electrolytes provide energy for muscles and help maintain blood volume during exercise, two important boosts to performance.
To fuel muscles during a marathon, the goal is to consume 30 to 100 grams of carbohydrate each hour. That’s the equivalent of 16 to 48 oz of Powerade each hour. For runners who don’t sweat much, 16 oz (500 ml) of Powerade each hour may be enough to keep them well hydrated. If they want more carb energy, they can pop a gel pack or some chews each hour. Heavier sweaters may require 32 oz (1000 ml) to 48 oz (1500 ml) each hour to minimize weight loss. If they rely on Powerade to meet those fluid needs, they’ll consume all the carbohydrate energy they need to power performance.
Running Examiner: Just how important is hydrating after the race?
Dr. Murray: The importance of hydrating after a race depends on how you’re feeling. If you are really feeling out of sorts, it’s best to head to the med tent for a quick exam to make certain that nothing serious is wrong. For the majority of marathoners, even for those who are dehydrated, there’s no real rush to rehydrate. Normal eating and drinking over the next 24 to 72 hours is usually sufficient to restore hydration. After all, few marathoners are going to be doing long training runs the day after a race, so post-race rehydration is not critical unless you’re severely dehydrated and feeling awful.
For all of the latest running news, tips, and gear reviews, please subscribe to the National Running Examiner. Updates are also available on Facebook at Running and Marathon News and on Twitter @RunWrite.