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The 10% Rule


"Finishing an ultramarathon is simple. All you have to do is not stop." That zinger comes from my latest book, but when you think about it, it really is true. Many endurance sports boil down to one thing: persisting until you reach the finish line. The challenge, of course, is how to reach that finish line as quickly as possible but still reach it. That's where the 10% Rule comes in.

Developed over years of strenuous research (i.e., many respectable finishes, with a few DNF's sprinkled in as educational lessons), I now use the guiding principle when racing to always keep 10% in energy reserves. On race day, I always remind myself to obey this rule or potentially face the consequences. Now, don’t interpret this as simply meaning to go slow. On the contrary, the concept is to push as hard as possible during each race stage, bumping up against that 10% energy reserve threshold throughout but never crossing over... until the finish.

Once you feel that strong gravitational pull from the finish line, the 10% Rule goes out the window. The idea is to push like a crazy person and give everything you've got, arriving at the finish and either puking your brains out or collapsing (special bonus points for both).

Try it on your next race and see if it helps you (feel free to skip the puking and collapsing part; that apparently is my specialty).

While the 10% Rule applies from the start, I make sure I'm 100% ready before the gun goes off. This includes taking 3 Race Caps Supreme, Fully Charged, Endurance BCAA+, and Anti-Fatigue Caps to help prolong my endurance from the very start. I continue using these throughout the race, along with other Hammer Nutrition products like HEED and Endurolytes Extreme. Assurance that you’re getting the best ingredients in ideal formulations goes a long way to boosting race day confidence.

Hammer on…

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Dean Karnazes is an ultramarathoner and Hammer Nutrition Athlete. He has raced and competed worldwide and once ran 50 marathons, in all 50 US states, in 50 consecutive days. His most recent book is A Runner’s High.


This regimen is one that I have used for most all my races; E-caps, HEED ans Perpetuem. My energy throughout the duraction of the race has always been more then enough to cross every start and finish line.
Hammer Nutrition replied:
Hi Chris, thank you for your comment! By E-Caps, I believe you mean Endurolytes and dates you back to the old days! Thank you for your long term support! BDF

Christopher Felix

Thanks, Dean. How do you find that 10%? How do you know when that’s what you have in reserve?
I swim. by no means a marathoner, but I’d like to apply this to my races.
I am a Hammer Sponsored Athlete and I use (and swear by) the products!!!
Hammer ON!
Hammer Nutrition replied:
Dear Sheila,

It is nice to be in touch with another Hammer Nutrition athlete! I swear by the products, too 😉

You ask a good question. One simple way to quantify output is using heart rate. If you know your lactate threshold, keep your heart rate at least 10% below that.

For me, a better measure is perceived exertion. I know early in a race I will have excess energy and in later stages will be more fatigued. Having run hundreds, if not thousands of races, I now have a good idea of when I’m bumping up against that 10%, and back off accordingly. So try to push yourself in your training (at all stages) and get a familiarity what it feels like to cross the line and overexert.

I hope that helps, at least a little. I’ve done some open water swimming myself, total respect for what you do.

Keep hammering, Dean

Sheila Carpenter-vanDijk

where are the athlete studies on the products mentioned????
Hammer Nutrition replied:
Hi Rick, The “research” that Dean alludes to is anecdotal- his own trial and error. This is not a scientific article. BDF


At what point does filling your belly up with pills become a problem? How does the gut respond to the amount of plastic it has to process?
Hammer Nutrition replied:
The majority of our supplements are contained within all-vegetable capsules (plant cellulose and water), which are very rapidly dissolved. The supplements that come in a liquid form (e.g., CBD softgels) are contained within a gelatin capsule. Gelatin capsules are not only easily dissolved, the gelatin is actually quite good for supporting healthy joints. No plastic is found in the capsules we use, and because the capsules we use are so rapidly dissolved, there should never be any gut issues, even when taking multiple supplements at one time.


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