Cramping ยท about four minutes
Half the field has cramped. The fast ones cramp more.
Which is the first clue that the story you have been sold about it is wrong.
How common it actually is
Two independent risk factors came out of that data. One was having cramped before. The other was a faster race time.
That second one matters, because the implied story in most training advice is that cramping is a sign you were not ready. The data points the other way. The people cramping are disproportionately the people going hard enough to be near the front.
What the research says the cause is
The fatigue hypothesis has carried this literature for over a decade. Cramping is driven by neuromuscular fatigue: increased muscle-spindle excitatory activity together with decreased Golgi tendon inhibitory activity. The control loop that normally tells a muscle to stop contracting loses its brake.
At Western States, cramping was unrelated to total sodium intake rate or volume. A separate ultramarathon study found impaired fluid and sodium balance did not appear to be an etiology of cramping at all. Studies have repeatedly found no association between cramping and serum electrolyte changes.
Which is awkward for us, and we are going to say it anyway
There is 800mg of sodium in what we make. We are not going to tell you it stops your legs seizing at mile eighty, because the research does not support that and we would rather lose the sale than make the claim.
Almost every brand in this aisle sells salt for cramp. It is the most reliable pitch in the category and it is not supported by the evidence. We cut that claim from our own copy for that reason, and the cut is written down publicly.
What the evidence does point toward
- Managing accumulated fatigue rather than accumulated salt: pacing, durability work, and training that resembles the demand.
- Treating a prior history of cramping as a genuine risk factor rather than as bad luck, because the data treats it that way.
- Checking what else you are taking. Magnesium oxide is absorbed at about 4%, and the portion you do not absorb stays in the gut, where it is associated with the bloating and cramping people often blame on the effort itself.