Each week, I ask a question about a common running science myth. Answer correctly and you'll be entered into the weekly raffle.
When you look at runners who cramp vs runners who don’t during the same race, the biggest predictor of cramping is what?
A. Blood sodium level (the classic “salt loss” explanation) 🧂💧 (20.4%)
B. Total dehydration (percentage of bodyweight lost) ⚖️💦 (14.3%)
C. Running faster than your recent training pace — muscles going past what they’re prepared for 🏃💥 (54.3%)
D. A quad-to-hamstring strength imbalance 💪⚖️ (11.1%)
Why this is right
The “electrolyte imbalance” story is sticky, but the data doesn’t back it. Runners who cramp and runners who don’t have nearly identical blood sodium and hydration levels in the same race. The strongest predictor is running at a pace the athlete hasn’t trained for — under-prepared muscles firing past their tolerance.
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