Saturday, February 28, 2015

Dehydration Article in WSJ: CTS Response

This was in the weekly CTS email in response to a Wall Street Journal article re hydration. I had read the original article pretty much thought the same things noted below, namely that taking in fluids just because you think you should doesn't work and riding well into dehydration will likely affect performance in long events. It’s back! There are a few article topics that pop back up into mainstream media every year or two, like “too much exercise will kill you” and “you shouldn’t eat carbohydrates during exercise”. This week it was the “you’re drinking too much during exercise” chestnut that made it into The Wall Street Journal. There’s plenty of great information in the article, but as with so many of these articles it’s important to figure out how the information applies to you. The gist of the article (and I encourage you to read it first-hand) is that the long-held guidelines regarding hydration – consume enough fluids to prevent bodyweight loss greater than 3% during activity – are outdated because new research shows that athletes don’t experience a drop in performance when they lose that much bodyweight – and more – during exercise. The aim is to move athletes away from drinking on a schedule to drinking based on sensations of thirst. And they raise the specter of hyponatremia to drive home the point that overconsumption could kill you. FirstOffice_462x462COACHING SPECIAL: FIRST MONTH FOR $15! CTS is 15 years old! To celebrate, your first month of coaching is just $15! Offer is valid on all coaching package levels for new coaching signups in the month of February! I have no disputes with the science presented in the WSJ piece, but even with the addition of some new studies we’ve seen this information and these recommendations before. In fact there was a piece by Alex Hutchinson (Sweat Science) from 2013 that covered the science and debate quite well. My issue – then, now, and the next time this comes up – is that there’s no one-size-fits-all solution for hydration. Here are some perspectives to take into consideration when thinking about if and how the WSJ article applies to you: ELITE ATHLETES TAKE RISKS TO WIN RACES Some of the examples cited in the article include the fact that Dean Karnazes runs cool-weather marathons without drinking, that Meb Keflezighi (winner of the Boston Marathon) loses 3-4% of his bodyweight and still wins, and that faster marathon finishers lose more bodyweight during races than slower marathon runners. The inference is that if the top performers can lose more weight than the long-standing guidelines and still perform and win, then you can too. But part of what makes an elite athlete an elite athlete is the ability to psychologically and physically endure more than average athletes can and certainly more than novices are prepared to. Years of practice and trial and error have taught them how to gauge their intensity and manage their fluid intake. They also know that losing too much fluid weight and overheating could destroy their performance, but they push that limit as far as they can in order to win. It’s the old “In order to win you have to risk losing” mantra. But it’s not wise to extend that expectation to middle-of-the-pack or back-of-the-pack marathoners, triathletes, and cyclists. IT’S NOT THE WEIGHT, IT’S THE HEAT So, why does it matter how much water you lose during exercise? It matters because the fluid in your body is what gets pushed out onto the skin as sweat to evaporate and help you manage core temperature. The higher your workload (faster pace), the more heat you generate. When core temperature rises, motivation to continue at a high workload diminishes, even before there is a physical response to reduce workload. A cool environment, water poured on the athlete, or ice packs can reduce the reliance on sweat for this cooling. This can enable an athlete to blunt the increase of core temperature despite a significant loss in total body fluid weight. In the Sweat Science article referenced above Alex Hutchinson cites a study that didn’t show a change in performance or a big increase in rectal temperature during a cycling time trial in 33C (91.4 degrees Fahrenheit) heat when subjects were 0%, 2%, or 3% dehydrated. But the time trials were only 25km (approx. 15miles) and the athletes were continually infused with fluids to maintain their level of dehydration. In the real world the issue of controlling core temperature is complicated by the fact that events are often much longer than 15 miles, environmental conditions change (it gets hotter or colder during the event), and athletes have to remember to replenish fluids and have them available. LOSING WATER WEIGHT MAKES YOU LIGHTER, AND BEING LIGHTER IMPROVES PERFORMANCE. The statement above is paraphrased from the WSJ article, and it’s correct. Talking to Jason Koop, my top ultrarunning coach, he tells his athletes that the percentage weight loss is about equal to the performance gain. Basically, once you lose 2% of your bodyweight during a run you can sustain a pace that’s 2% faster. The impact is likely greater for runners than cyclists, though, because runners have to lift their bodyweight with every stride. The problem is, there’s a balance point involved here. Up to a point, losing some water weight might be advantageous because your power to weight ratio will go up. But then the core temperature problem catches up to you and power/pace drops, eliminating the advantage. And what’s worse, getting an athlete back to optimal function after they’ve tipped over that edge isn’t quick. If you have already optimized everything else and you’re still looking for that edge that might get you a PR or a win, then mild dehydration for weight loss might be an option. But for most athletes there are a lot of other steps that can improve race-day performance before needing to accept the risks involved in this strategy. Tour of California Race Experience The Tour of California route has been announced! Check out the video and then come and ride every stage with me, experience VIP access to the course and the finish areas, and share your meals with the pro teams. Space is getting very limited for this trip but you can still get in on this Bucket List event if you act now! THE HUMAN BODY HAS NO WATER GAUGE So, let’s assume that slight dehydration is actually good for performance but that overheating and excessive fluid loss is bad for performance. In the middle of a race how are you going to determine your hydration status? A scale? Pee sticks? Rectal thermometer? When it comes to workload we can measure power output and pace, but the body has no water gauge. Tim Noakes says to use the sensation of thirst. I think the sensation of thirst is useful, but it is just one factor in determining how much fluid to consume and when. There are a lot of variables to consider: ambient temperature and humidity, changing temperatures during the day, the duration of the event, athlete’s intensity level, the availability of fluids, the athlete’s ability to carry fluids, etc. Is your sensation of thirst so attuned you can account for all these variables? And perhaps the bigger issue is whether an athlete will actually respond to the sensation of thirst! Athletes get tired. They get fixated on holding a wheel or staying at a certain pace. They forget to drink; they forget they’re thirsty. Sometimes they just don’t care that they’re thirsty or they remember they’re thirsty when there’s no water available. A hydration strategy or schedule is not about pounding fluids or drinking despite signs you don’t need to. It’s about making sure athletes are engaged enough to make the decision to drink or not to drink, and to make sure they have fluids available when they need them. Availability is less of a problem in road marathons where you’re never more than a mile from water. But it’s huge consideration in ultramarathons, road cycling and MTB events, and Ironman triathlons (at least the cycling leg). IF YOU TAKE AWAY NOTHING ELSE… Hydration is extremely individual and the best thing you can do is start with a strategy or schedule and adjust as needed based on the environment, your intensity, your sweat rate, and what your body is telling you. On the grand scale of hydration guidance, you can think of purposeful dehydration for improved performance and the risk of hyponatremia as the opposite ends of the spectrum, and there’s a huge range of options between these extremes. Over the years I have gathered a pretty good sense for the audience this blog reaches. On average you are a group of reasonably experienced and educated athletes who train consistently and compete or participate in several events each year. If that description describes you, then there is plenty of room between those extremes to find what works best for you. Your risks of hyponatremia are remote and there are better ways to improve your performance than purposely dehydrating yourself during your next race. Have a Great Weekend, Chris Carmichael CEO/Head Coach of CTS

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