Human performance vs survival: what is optimal hydration

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Here we are, summer approaching with the warm temperatures I love the most. But with summer comes the fear mongering about dehydration, as well the gimmicks and snake oil being sold promising to bring you to your best performance. As I have discussed on a previous podcast, the risk of over drinking is very real, and far outweighs the potential harm of drinking too little. However, it goes deeper than that, because really, no one goes out anymore with the intention of not drinking. We get thirsty and we drink what’s available, just like Paleo did for tens of thousands of years. The difference is, he didn’t have water stops and hydration packs, nor was his aim to PR. Survival was the name of the game, and he did it well; I use he here, because men typically hunted. My objective in this latest article is to present some evidence as well as thought provoking experience and commentary to the endless hydration debate, and make my own recommendations on hydrating for performance.

In the beginning…

Modern man has lived and died by his wits and physiology. Let’s face it, we’re top of the food chain and unraveling this world at record pace. But at least some of us will survive because we’re built for it. I ascribe and truly believe that our physiology is designed to survive and overcome, not fail at the slightest imbalance. Yet it continues to amaze me that we’ll buy into the “mommy instincts” and yet ignore the precision of our internal thirst

Survival vs Catastrophe: what is your perspective?

When considering hydration guidelines the first thing we need to do is decide whether we believe the human body is a supremely adaptable machine that is capable of surviving in nearly any earthly environment (has evolution has proven), or it is flawed and not very “smart”, ready to catostrophically fail in any extreme (as Gatorade and some of their funded scientists have suggested). If you believe the latter, then drink as much as possible and do not read any further.

Obviously, lab and real world experience has shown us that the former is true, and that very few cases of sport related dehydration leading to severe injury or death have been reported; take care in not confusing dehydration with heat related incidents, because the two are not causally related. This is an important point, because many cases of heat related illness occur, and over drinking leads to far more injuries/deaths than dehydration has. Further, as Tim Noakes points out in his book Waterloggedsymptoms often blamed on dehydration (lethargy, headache, confusion and dizziness, nausea, edema, fainting) are not related to dehydration at all, but may in fact be symptoms of hyponatremia; in other words, using an IV could actually kill someone believed to be dehydrate! Moreover, when someone crosses the finish line and faints, it is related to exercise-induced low blood pressure. Before we start injecting drugs into them, try lying them down and elevating their feet. It is likely they will recover within minutes. While they’re lying there, ask them if they are extremely thirsty. If the answer is no, they are not likely “dehydrated”.

Why does this relate to Paleo? Because, humans are overbuilt with redundancies. Paleo, and even contemporary hunter-gatherers, are able to walk and run 8-12 hrs on a hunt with little or no water and not die. Even if we try to make the case that they are more fit and better adapted, all we are really doing is arguing for better training, not more water stations.

FACT: before the 1980’s few people ran a marathon in more than 3 1/2 hrs, but few people ran marathons.

I am sorry if I offend anyone, but we have created an industry of coddled conditioning where “everyone can do it” and finishing is the only goal, no matter how slow. Now I’m not saying that only fast people should compete. However, setting real performance goals with specific times and training plans to compliment one’s ability and meet their goals is the path to real success. Anyone can just finish. We (the fitness-related industry that includes many bad trainers and coaches) half put together innumerable half-assed approaches to help people meet the minimum standard often by lowering the bar; consider that the pull-up has been replaced by the bar hang! It’s also worth noting that many runners gain weight while training with marathon training teams. Research presented at the ACSM annual meeting (sorry, I cannot find a link to the abstract) suggested that excessive feeding during and after training leads to a weight gain of up to 12 lbs. For anyone running a 9 min/mile or slower in training, 200-300 kcal per hour should be more than adequate fuel.

Sweating away your performance

In my life as a cyclist, I made the most of resources had and if I was dehydrated it was not by choice. Which is why many of the drinking recommendations are folly, because many cyclists simply cannot meet those unnecessary recommendations. The belief that a 2% loss in body weight leads to diminished performance is arguable, particularly when we examine real world performance data. Noakes reviews several lines of field data from the IM South Africa and marathon performances. It all points in one direction; the fastest finishers tend to lose the most weight. One specific example is from the the 2008 Berlin Marathon where Haile Gebrselassie set a marathon world record. During the Dubai Marathon, which he also won, he drank 0.83 L/hr, sweated at an estimated 3.6 L/hr, and lost nearly 10% of his body weight! Based on what I learned in college, Haile should have died in that race.

Obviously Gebrselassie is a supreme athlete, but he is still human, and thus no different from you or I. So how could we lose so much weight and not suffer for it? The answer likely lies in one of the longest modern recommendations for endurance athletes, carbohydrate loading. For every gram of stored glycogen in the body, there are 3 grams of water stored with it. When the glycogen is used, the water remains in the body and can be used as such. To put it another way, we need to be sure that the weight loss we are seeing is actually from water we have ingested and stored in the body as plasma. If we assume that carb loading leads to 500 g of glycogen, then total pre-race weight gain would be 2 kg, or nearly 5 lbs. If we drain all those stores during a hard race and sweat out the water stored with it; for a 140 lb athlete, that’s 3.5% body weight. Add another loss of 1.5% for plasma in sweat and you’re at 5%. For a guy Haile’s weight, he could still store at least 500 g of carb, but at 123 lbs its closer to 4%. The point is that the 2% loss just does not hold up in the real world, partly because sweat rate is tied to metabolic rate more than temperature and hydration does not impact actual cooling ability. Again, we are talking about correlations here, not causal factors.

Paleo meets the modern world

The purpose of this article has been to make us all think about what we need to do to survive versus perform optimally. I believe there is a mountain of data that supports the fact that you can compete with little fear of dehydration health impairment; i.e., dehydration is not dangerous in an event lasting 2 hrs or less, or conducted at a slow pace (i.e., 4+ hr marathon). However, this does not mean you do not need to drink anything. The fact is, thirst is an adequate signal for drinking. I have days when I am less thirsty and drink less, and days when I’m “dying of thirst” and drink more. In XTerra race situations, I use my estimated sweat rate (an overestimate to begin with) to determine how much fluid I need for the bike and carry that much fluid in my hydration pack, but also carry at least one 24 oz water bottle (my extra “thirsty” fluid). During running races of 1 hr or less, I rarely drink much at all, and in more than 1 hr, I drink to thirst. Everyone’s thirst level is different, so if you want, calculate your sweat rate and track your fluid intakes and see what works best for you. Because at the end of the day, the best strategy is the one tailored to the individual!

NOTE: I recommend reading Tim Noakes Waterlogged to at the least gain another perspective to the heavily weighted Pro-Gatorade version of the hydration debate. It costs just $10 as an e-book.

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