The cramp hits at kilometre 30. Someone on the sideline shouts the same thing they always shout: “You need salt!”

It is the most repeated cramp advice in endurance sport.

It is also the one the strongest evidence does not support.

Why the salt theory is so sticky

The story is intuitive. You sweat, sweat is salty, you cramp — therefore the lost salt caused the cramp, and replacing it must be the fix. It also comes with a ritual that feels like control: a tablet you can take, a number you can track. Intuitive and reassuring are not the same as correct.

What the evidence actually shows

When researchers examined the electrolyte-and-dehydration theory, it held up poorly. Support came largely from anecdotal observation, small case series, and a single small case-control study — while several prospective cohort studies found no link.^[1]

The model with stronger support is different. Exercise-associated cramp is now thought to be multifactorial, driven primarily by an imbalance between the muscle spindles that excite a muscle and the Golgi tendon organs that inhibit it — an imbalance produced by neuromuscular overload and fatigue, rather than by lost salt or water.^[2]

The clue hiding in the cure

The most reliable way to stop a cramp that is already happening is to stretch the muscle.^[2] Passive stretch increases tension the Golgi tendon organ can sense, restoring the inhibitory signal that tells the muscle to release. It acts directly on the neuromuscular loop — and does nothing to your sodium levels.

If cramp were a salt-deficiency problem, the universal front-line fix would not be a mechanical one that leaves your electrolytes exactly where they were.

The difference is easier to see than explain.

The honest exception

Before you throw your salt tablets away, there’s one important exception — because a blanket “electrolytes are irrelevant” would overstate the case, and this series does not trade one myth for another. In specific groups — notably very heavy, salty sweaters in prolonged heat, studied most in American-football players — sodium loss does appear to contribute to cramping.^[3] That is a defined subgroup, not the general endurance athlete, and it does not rescue the universal claim that salt tablets prevent cramp for everyone.

Why this matters more in Singapore

Training in Singapore’s mean annual humidity of around 82% and inter-monsoon temperatures above 32°C^[4] means high sweat rates and salty shirts — which makes the salt theory feel self-evidently true. But heat drives cramp mainly by accelerating fatigue: you work harder to cool yourself, your muscles tire sooner, and the neuromuscular imbalance arrives earlier. The heat is real. The mechanism is still mostly fatigue.

What actually helps

Train for the specific demand of your event so the working muscles fatigue later. Pace sensibly early. Build heat acclimatisation so a given effort costs less. And fuel adequately — carbohydrate depletion is itself a contributor to the fatigue that precedes cramp, which is where your wider race-fuelling plan earns its place. Work that out with the Race-Day Fuelling Calculator.