The 1-Hour Rule: Where Did It Come From?

The Source

The American College of Sports Medicine has long included guidance that for sessions over about 60 minutes, particularly in heat or at moderate-to-hard intensity, a drink with carbohydrate and electrolytes can be useful. This is where the casual "1-hour rule" comes from - though as with most rules of thumb, the underlying picture is more nuanced.

Why 60 Minutes Specifically

The number isn't a hard physiological boundary. It's a reasonable cutoff that reflects how long stored glycogen typically lasts at moderate-to-hard intensity in well-fed athletes, and how long sweat losses tend to accumulate before they become meaningful to performance and comfort.

The Modern Picture

Several things complicate the simple rule. Intensity matters - a 45-minute interval session at race pace asks more of fuel and fluid than a 90-minute easy ride. Climate matters - sweat rates in 35°C heat outpace those in 18°C. Individual variation is large. And the daily-hydration use case (drinking electrolytes at the desk to support general fluid intake) sits outside the original exercise framing entirely.

Practical Translation

For sessions under an hour in mild conditions at conversational intensity, water plus normal eating is fine. For sessions over an hour, particularly hard or hot ones, an electrolyte product earns its place. For multi-hour endurance days, in-session carbohydrate and sodium both matter.

The 1-Hour Rule as a Starting Point

Treat it as the starting point, not the answer. Many readers will refine their own version of the rule through their own training - "after 90 minutes for me," or "any session over 60 minutes if it's hot." That's how rules of thumb are supposed to work.

Frequently Asked