You ate the banana. You drank the electrolyte water after your run. Someone at the gym said low potassium causes muscle cramps, and the advice was so universal you never questioned it. The cramps came back anyway.
It wasn't that you took too little. It's that the question itself had two separate stories collapsed into one.
Does Low Potassium Actually Cause Muscle Cramps and Weakness?
Exercise-associated muscle cramps show no connection to electrolyte levels across four prospective studies in athletes. Clinical hypokalemia does cause cramps and weakness, but symptoms don't appear until serum potassium drops below 3.0 mmol/L, a threshold that reduced dietary intake alone almost never triggers because the kidneys conserve potassium.
— Maughan & Shirreffs 2019 · Sports Medicine (4 prospective studies reviewed) + Castro & Sharma 2025 · StatPearls
The idea that exercise cramps come from electrolyte loss sounds like settled science. Underneath, the foundation is thinner than you'd expect: anecdotal clinical observations, case reports adding up to 18 people total, and one small case-control study. That's what the universal advice about sweating out potassium was built on.
Four prospective studies tracked athletes through endurance events and measured electrolyte levels before, during, and after cramping. Zero association between electrolyte changes and exercise cramps. Not one found a link. The evidence everyone assumed existed wasn't there.
That zero is where the question cracks open. Because potassium cramps are real. They're a medical event, not an exercise event.
found a link to potassium Exercise cramps
cramps actually start Potassium deficiency
Clinical potassium deficiency causes genuine muscle weakness and cramping. But symptoms don't even show up until your potassium drops below 3.0 on a standard blood test, well past what anyone eating normally ever reaches. The people who get there are usually on diuretics, dealing with prolonged illness, or managing a medical condition. Not someone who skipped a banana.
Your kidneys are so efficient at conserving potassium that reduced dietary intake alone almost never causes deficiency. The body already regulates what the supplement was trying to do. The banana was solving a problem that barely existed.
YOUR EXERCISE CRAMPS
Zero electrolyte connection across 4 athlete studies. Likely neuromuscular fatigue at the spinal level.
MEDICAL POTASSIUM DEFICIENCY
Real cramps below 3.0 on a blood test. Usually caused by medications or illness, not dietary shortfall.
Most exercise cramps are neuromuscular fatigue, sustained misfiring at the spinal level where the nerve signals controlling the muscle lose their rhythm. Not a mineral shortage. A fatigue signal that shows up when the muscle has been pushed past its capacity.
Neither hypothesis rests on airtight evidence. Both sides have limited data, and the leading view now is that different types of cramps probably run on different mechanisms entirely. One mineral, one fix, every cramp. That's the story the evidence does exclude.
The banana stays on the counter. The cramps keep their own schedule. What stopped one cramp in 85 seconds never even reached the stomach. When magnesium faced the same test, the cramp promise dissolved. Where minerals genuinely matter and where they don't is a longer answer than any single cramp.