Experience From - Karl King, George Beinhorn

Karl King

Will Brown posted questions on PhosFuel. This was brought up before, so others can reiterate what they said before. Here are my views.

The product is intended to supply pH buffers which are effective in

  1. the stomach
  2. the blood
  3. muscle tissue
It is effective, using very simple chemistry whose effects are well documented and understood; there's no "black magic" with this.

The intended purpose is for short-term, anaerobic exercise which produces considerable amounts of acid. The acids produced reduce energy output by making certain enzymes in the muscles less efficient. By counteracting and neutralizing the acids, energy production can be maintained for a longer period of time. The formulators did not, I suspect, ever think of it being used in endurance events.

The product supplies major amounts of sodium phosphate, a simple buffering salt. You can overdose yourself with sodium if you take too much. The label advises to not take it on a daily basis and the body would readjust its chemistry to dump most of the contents into the urine, defeating the purpose of taking it.

It also supplies potassium bicarbonate, another simple buffering agent. This is also significant source of potassium.

It also supplies a number of useful B vitamins.

Why might it be useful in an ultra?

It supplies plenty of electrolytes in a balance that is quite good for endurance running.

It reduces system acidity which can build up during many hours of running on mostly carbohydrate foods.

It supplies B vitamins which are necessary for energy production and not found in great quantity in the foods normally found at aid stations.

It supplies phosphate which is needed for energy production ( but which is common in many other foods, Coke being one example ).

So, it is not used in ultras in the way it was originally intended to be used, but so what - it supplies ample quantities of useful substances. One thing it would be good to add is magnesium, as that is needed in endurance running.

I find it useful in any short race ( 5-10K ) and in any ultra. For short distances, follow the directions on the label. For ultras, skip the pre-load described on the label and take only during the event. Some runners find it useful afterward for recovery. My experience is that if you take it during the run, it is not needed afterward. But, try it for yourself and see what works for you. Just remember that it is not candy.

The effective dose in an ultra could vary with conditions. What seems reasonable based on my experience is one at the start, and one every four hours or so. In hot weather it might be useful to take every 2-3 hours.

A few runners have told me that they had excellent results with this during an ultra. My opinion is that they had reached a state of electrolyte imbalance that was pretty serious, and the PhosFuel corrected that, putting them back into a state where they could run normally again.

Note that none of the contents are drugs. They are all found in the human body, so this is not like taking something unusual. In that sense, it is a more natural product than caffeine or ibuprofen, neither of which is a normal body constituent.

There is another product on the market which is virtually identical in composition: Forced Reps by Beverly International.

You can take PhosFuel with or without foods. It will be more effective if it is taken with low-acid foods. Many ultra runners end up with overly acid stomach and small intestine because

Avoid sodas and coffee in large doses. Eat some fat and protein along the way. That is good in any case, but will increase the effectiveness of the buffering agents in PhosFuel.

Disclaimer: I have no financial interest in any product mentioned above.

George Beinhorn

I used PhosFuel in two long runs: a hard 23-mile training run, and a 30K race. In the 23-miler, PhosFuel appeared to do me no good at all; it may even have made me feel worse.

In the 30K, PhosFuel was disastrous. I did the phosphate loading routine as described on the bottle, taking 2-3 pills per day for several days before the race. During the race, I took 1 pill 1/3 of the way through (if I remember rightly). I felt really lousy, but after six miles I began to recover. I was running well, but toward 13 miles my legs began to tire a little, and I thought I'd take 2 PhosFuel and see what happened. With two miles I was desperately wanting to walk, and had slowed to 10-minute pace (from 7:30-ish).

I've found PhosFuel very useful for recovery. After a hard run, I take 1 PhosFuel, then I take one the next day. I feel it perceptibly speeds my recovery. But despite good reports of its use during 100-milers by very experienced ultrarunners, I will not use it in races or training runs. Each body has its own needs; mine appears to be PhosFuel-unfriendly.