By Steve Born
At Hammer Nutrition, we consistently deal with many fueling myths, and I’d rate the replace what you lose approach as probably the worst offender of all. Many organizations and alleged experts continue to recommend that athletes need to replace what they expend during exercise in equal or near-equal amounts, hour after hour. They cite data such as you lose up to two grams of sodium per hour, burn up to 900 calories hourly, and sweat up to two liters an hour to defend their position. Even worse, sometimes they don’t give any numeric guidelines, just vague statements like take salt tablets or drink as much as you can. Sadly, far too many athletes fuel their bodies exactly this way and they get only poorer-than-expected results or a DNF to show for their efforts.
The figures that the replacement proponents cite are often valid: a vigorously exercising athlete, especially a big guy, can really expend significant amounts of fluids, calories, and sodium. We don’t argue at all with most expenditure figures. However, expenditure just isn’t the appropriate measure to guide your fueling, it is what you can effectively assimilate. Don’t go by what you burn/lose, but rather what the body can reasonably absorb and process during any given period of time.
The statements on page 15 from Dr. Bill Misner represent our position on what proper fueling is all about. What this means is that the body cannot replace fluids and nutrients at the same rate it depletes them.
“To suggest that fluids, sodium, and fuels-induced glycogen replenishment can happen at the same rate as it is spent during exercise is simply not true. Endurance exercise beyond 1-2 hours is a deficit spending entity, with proportionate return or replenishment always in arrears. The endurance exercise outcome 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.”
“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.”
Yes, the body needs your assistance in replenishing what it loses, but that donation must be in amounts that cooperate with normal body mechanisms, not in amounts that override them. Here’s an important fact to keep in mind: at an easy aerobic pace, the metabolic rate increases 1200-2000% over the sedentary state. As a result, the body goes into survival mode, where blood volume is routed to working muscles, fluids are used for evaporative cooling mechanisms, and oxygen is routed to the brain, heart, and other internal organisms. With all of this going on, your body isn’t terribly interested in handling large quantities of calories, fluids, and electrolytes; its priorities lie elsewhere.
Your body already knows it is unable to immediately replenish calories, fluids, and electrolytes at the same rate it uses/loses them, and it has the ability to effectively deal with this issue. That’s why we don’t recommend trying to replace hourly losses of calories, fluids, and electrolytes with loss amounts. Instead, we recommend smaller replenishment amounts that cooperate with normal body mechanisms. We’ll discuss this in more detail later in the article.
What does research show regarding replenishment?
The “Loss vs. Assimilation” table below is a suggested comparison showing approximated upper values for what is lost during prolonged endurance exercise to the maximal amount that can be successfully absorbed, replaced, and routed into the energy cycle for the average-size endurance athlete (160-165 lbs/72.5-75 kg) who is fit and acclimatized.
Loss vs. AssimilationWhat can your body really handle? |
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| SUBSTANCE | RATE LOSS/hr | ASSIMILATION RATE |
| Fluids (ml) | 1000-3000 (30-90 oz) | 500-830 (17-28 oz) |
| Sodium (mg) | 2000 | 500-700 |
| Calories | 700-900 | 240-280 |
| Below are the corresponding replenishment values that we have observed for the averagesize endurance athlete (160-165 lbs/72.5-75 kg) who is fit and acclimatized (+/-5%): | ||
| SUBSTANCE | IDEAL REPLENISHMENT | |
| Fluids | 20-33% | |
| Sodium | 20-35% | |
| Fuels (Calories) | 17-28% | |
| References: | ||
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As you can see, there is a tremendous difference between what is lost and what can effectively be replenished during exercise. For calories, on average only 17-28% of what is utilized (burned) can be efficiently replenished. In general, fluids are replenished at a rate of only 20-33% of what is spent, and sodium 20-35%. What’s important to keep in mind is that the body is keenly sensitive to this, recognizing its inability to replenish what it loses at anywhere near the rate that it’s losing it.
For example, body fat stores satisfy upwards of two-thirds of energy requirements, very easily making up the difference between what is burned and what the body can accept in replenishment. For the majority of athletes, calorie oxidation rate and gastric absorption rate typically allow for no more than 240-280 calories per hour, at the most, to be consumed for successful gastric absorption to energy transfer. Consuming greater than that amount increases the potential for a number of stomach/digestive distress issues.
In regards to body fluid volume and serum sodium concentration, both are controlled to a degree by hormone pathways between the brain and internal organs. As Dr. Misner stated, the body has remarkably complex and efficient built-in survival safeguards that very capably deal with the difference between what it loses and what it can accept in replenishment. The various systems involved are complex, but the bottom line is that only a relatively small consumption will keep you going. On the other hand, over-consumption can easily throw the systems out of whack.
This is why we are so adamant about the less is best way of fueling. For example, if you err on the not enough side in regards to calories, that’s a very easy problem to fix, you simply consume more calories. However, if you over-supply your body with too many calories, that’s a much harder (and longer) problem to resolve (at the very least you’ll have to deal with an upset stomach for quite awhile). The simple truth is that once excess amounts of calories, fluids, and/or sodium are in your body they’re not coming out, at least not the way that you want them to! Bottom line? Over-supplying your body will absolutely not enhance athletic performance but will most definitely inhibit-or-ruin it.
Of course, there are many individual variations that you will need to consider (age, weight, training/racing stress, fitness, acclimatization levels, weather conditions) to determine what works best for you. Some athletes will need less than these suggested amounts, a handful slightly more. Certain circumstances require flexibility; for instance, hot weather and high-impact exercise, such as the run portion of a long-distance triathlon. Hot weather usually means lower hourly calorie intake, a slightly higher fluid intake, and an increased electrolyte intake. High impact exercise such as running does better with roughly 30%-50% lower caloric intake per hour than what you’d consume during a less jarring exercise such as cycling.
All of this said, the figures listed make good starting points for determining your ideal intakes for varying conditions and circumstances. As far as calorie intake is concerned, we highly recommend that you use our weight-specific dosage suggestions, which are listed in the article THE HAMMER NUTRITION FUELS – What they are and how to use them in the supplement to this guide.
Fueling variability among athletes
There is no “one size fits all”!
The data from athletes who suffered poor performance due to fueling-related problems
- Fluid intake was almost always over 30 fluid ounces (887ml)/hour.
- Body weight at finish was hyper-hydrated with weight gain from 1-2%, or dehydrated at over 3% body weight loss.
- Excess calorie consumption, at or greater than 240-280 cal/hr, primarily from simple sugared-based fuels, causing stomach shutdown.
- High sodium diets. Athletes who consume this type of diet are predisposed to higher sodium intake during an event than the low sodium purist.
- Ultra distance athletes who suffered cramps, sour stomach, malaise, and/or hyponatremia in the last half of their event often did not train adequately at race-level fluid/fuel/electrolyte dosing, or the athlete used a different fueling protocol than in training. Athletes need to not only train appropriately leading up to their race, they also must test, evaluate, and fine-tune their fueling plan in training prior to using it in a race.
The data from athletes reporting success (no fuel-related, performance-inhibiting problems and consistent energy levels)
- Fluid intake was at or under 28 fluid ounces (828ml)/hour.
- Electrolyte intake via Endurolytes was between 3-6 capsules/hour, with 4 capsules/hour being the most often reported dose.
- Calorie intake was at 120-150/hour or less.
- Body weight at finish decreased no more than 2-3%.
What you should derive from all of this is that while there is no one size fits all fueling formula, there are some good guidelines in terms of what has been shown to be successful for athletes and also consistent observations (read: fueling errors) noted from athletes who had unsuccessful races.
Our Fueling Recommendations
Based on what science has shown us, plus over two decades of working with athletes, we have determined the following ranges as ideal for most athletes, the majority of the time, for maintaining optimal exercise performance:
| Fluids: | Sodium Chloride: | Calories: |
| 16-28 oz/hour | 100-600 mg/hour (1-6 Endurolytes) |
120-150/hour |
Summary
Proper fueling is consuming the least amount necessary to keep your body doing what you want it to do hour after hour.
We have been advocating the less is best recommendation for over two decades. Sadly, many athletes continue to listen to consume what you lose propaganda, arguing that nutrients and water need to be replaced immediately. This is neither true nor possible; fluids, calories, and electrolytes cannot be replaced 100%, or even 50%. As a result of following this flawed advice, athletes continue to experience cramping, vomiting, gastric distress, diarrhea, and other problems. The safe rule of thumb is to replenish at about one-third of loss values, obviously adjusting as conditions dictate.
As you read through our other fueling-related articles, you’ll see this principle applied repeatedly and further details given. It might seem like we’re banging the same drum all the time, but when it comes to fueling, we cannot emphasize enough that less is better than more. Rather than attempting to resolve your fueling requirements by replacing hourly loss with hourly intake, we suggest small doses, generally about a third of what is lost, if not lower. In conjunction with long-standing research regarding this subject, over two decades of successful experience with athletes testifies to the reliability of the less is best and fuel in cooperation with your body concepts. Yes, there are people who can complete events on high intakes of fluids, calories, and electrolytes, but the overwhelming majority of athletes are impaired or stopped by such fueling protocols. Athletes who do use less see their fueling-related problems end and their performance improve dramatically.
That’s why our battle cry is Less is Best! Remember, the goal of fueling is NOT to see how much you can consume and get away with before your body rebels, you end up getting sick, and your performance goes in the tank. Proper fueling is consuming the least amount necessary to keep your body doing what you want it to do hour after hour. And if you do err on the not enough side, that’s a much easier problem to resolve than an uh oh, I overdid it problem. We’re pretty darn sure that once you get away from those 500-700 calorie and liter-of-fluid-an-hour regimens, your body will perform much better, you’ll feel better, and you’ll get the results you trained so hard for.
