heed2Great and timely piece from Hammer Nutrition’s fueling expert, Steve Born.

Optimum nutritional support for endurance athletics means consuming the right amount of the right nutrients at the right time. You can neither overload nor undersupply your body without compromising athletic performance and incurring detrimental results.

Of all the entities of fueling—calorie intake, electrolyte replenishment, and fluid consumption—it is the latter that I believe is the most important to figure out and nail down. Why? Because it is improper hydration that has the most serious consequences attached to it. Consume too many calories? Your stomach will rebel with all sorts of unpleasant consequences (bloating, vomiting, diarrhea, etc.) Consume too much salt? Among other things, your body will exhibit—and you will experience—bloating as well as extremely unpleasant and performance-inhibiting edema-like symptoms of water retention.

Botch it on the fluid intake, however, and you can run into some very serious problems. If you don’t drink enough water, you’ll suffer from painful and performance-ruining dehydration. Drink too much, however, and you’ll not only end up with impaired athletic performance, you may even be flirting with potentially life-threatening water intoxication.

One of the most respected researchers on hydration, Dr. Tim Noakes, studied the effects of thousands of endurance athletes and noted that the front-runners typically tend to dehydrate, while over-hydration occurs most often among middle to back-of-the-pack athletes. Both conditions lead to hyponatremia (low blood sodium), but through different processes. Excess water consumption causes what is known as “dilutional hyponatremia,” or an overly diluted level of sodium and electrolytes in the blood. This is as bad as under-hydrating in regard to increased potential for muscular cramping, but has the added disadvantages of stomach discomfort, bloating, and extra urine output. And, as mentioned earlier, in some unfortunate circumstances, excess hydration can lead to severe physiological circumstances, including death.

Another expert on hydration, Dr. Ian Rogers, suggests that between 500-750 milliliters/hour (about 17-25 fluid ounces/hour) will fulfill most athletes’ hydration requirements under most conditions. I believe all athletes would benefit from what Dr. Rogers says: “The American College of Sports Medicine in its position statement, currently recommends a fluid intake during exercise of 600-1200 mls/hr. The fluid intake of most of the reported cases of exercise associated hyponatremia has been at the middle or upper end of this range challenging this as an appropriate fluid intake. A more realistic intake is likely to be 500-750mls/hr. While the old mantra, ‘If you don’t drink you die’ is not yet dead, it has certainly been challenged. We can no longer assume that excess fluid taken during prolonged exercise will just be passed out in the urine. Like most things in life, balance is the key and the balance is likely to be at a fluid intake not much above 500 mls per hour in most situations, unless predicted losses are very substantial.”

How much fluid should you drink?

• For lighter-weight athletes or those exercising in cooler temperatures, 16-18 oz./ hr. (approx. 473-532 ml) may be perfect.

• Average-size athlete, average temps – 20-25 oz./hr. (approx. 590-740 ml/hr.) is an appropriate fluid intake for most athletes under most conditions.

• Heavier athletes or athletes competing in hotter conditions may consider intakes upwards of 28 oz./hr. (approx. 830 ml/hr).

For satisfying hydration requirements prior to a workout or race, there have been a number of recommendations presented over the years. These are the two that we believe to be the most sensible, the ones that will satisfy hydration needs without putting you at the risk for over-hydration:

• One liter of fluid (about 34 ounces) in the two hours prior to the start (about 17 ounces/500 milliliters per hour), ceasing consumption about 20-30 minutes before you begin the workout or race.

• 10-12 ounces (approx. 295-355 milliliters) of fluid each hour up to 30 minutes prior to the start (24-30 ounces total fluid intake).

Keep in mind that even though these are our recommendations; you need to determine what works best for your system and the particular logistics of the race or training session ahead.

Fluid intake suggestions apart from the workout or race

For your regular daily hydration needs (that is, in addition to your exercise-induced needs), no research has conclusively arrived at an RDA for fluids, but about 0.5-0.6 fluid ounces per pound of body weight (roughly 33-39 ml/kg) is a more accurate standard than the eight glasses a day commonly recommended for everyone. Multiplying your body weight in pounds by 0.5-0.6 will give you the figure, in fluid ounces, which you should aim for daily. Metrically, you’ll multiply your body weight in kilograms by about 33-39 and that’ll give you a good estimate, in milliliters, of what you should be drinking daily.

Caveat: If you have not been following this recommendation consistently, you’ll want to start increasing your daily water consumption gradually until you reach your target amount. If you increase your fluid intake too quickly it will overwhelm your body with too much fluid too soon, which may increase the potential for hyponatremia.


Paraphrasing Dr. Bill Misner, “The human body has so many survival safeguards by which it regulates living one more minute, that when we try too hard to fulfill all its needs we interfere, doing more harm than good. To suggest that fluid replenishment can happen at the same rate it is spent during exercise is simply not true. The goal of fueling during endurance exercise is to postpone fatigue, not to replace all the fuel, fluids, and electrolytes lost during the event. It can’t be done, though many of us have tried.”

Keeping in mind Dr. Misner’s words of wisdom, follow our guidelines to help you get your fluid intake amounts dialed in. You’ll feel better all throughout the day, you’ll enter a workout or race properly hydrated, and you’ll stave off both dehydration and over-hydration during exercise, which translates into improved performance.

Republished with permission. I’m a Hammer Nutrition sponsored athlete and I use a number of these products in my own training. Feel free to post questions! If you’re a first-time Hammer user, I have a referral code! You’ll save 15% on your first order and receive a goodie bag with about $100 in free sample products!