Brisbane is a subtropical marathon, and humidity is the variable that decides most race outcomes here. Sweat evaporates poorly in humid air, so you cool less efficiently, drift higher in heart rate at the same pace, and lose more fluid and sodium than the temperature alone predicts.
The fuelling answer is not simply drinking more water. Diluting yourself with plain fluid while losing sodium is how runners arrive at 32km bloated, sloshing and slowing. Carbohydrate and sodium together, taken on a schedule, is the plan that holds.
What the race demands
Course
Mostly flat riverside city loops
Season
Subtropical winter, mild temperatures with high humidity
Main risk
Humidity driving sweat and sodium losses above plan
Second risk
Over-drinking plain water and diluting sodium
Carbohydrate and sodium targets
- Sub-3:00: 70 to 90g of carbohydrate per hour from a dual-carb source
- 3:00 to 4:00: 50 to 75g of carbohydrate per hour
- 4:00 to 5:00: 40 to 60g of carbohydrate per hour
- Sodium: 500 to 1,000mg per hour if you are a salty or heavy sweater in humidity
HYDRAX CORE delivers 85g of dual-carb fuel and 980mg of sodium per serve, so hitting the numbers above is arithmetic rather than guesswork. HYDRAX PRIMER covers the pre-race window with 29g of carbohydrate and 1,313mg of sodium. Run the free fuelling strategy tool to convert these ranges into your own per-hour numbers.
Rehearse the plan in training, then race it. Order now, ships Australia-wide.
Race week and race day timeline
2 to 3 days out
Carb load toward 8 to 10g per kg per day, low fibre in the last 24 hours.
Race morning, 3 hours out
Rehearsed carbohydrate breakfast plus fluid with sodium rather than plain water.
25 to 40 minutes out
One serve of PRIMER for 29g of carbohydrate and 1,313mg of sodium before you start sweating.
From 30 minutes in
CORE at your target rate. In humidity, err toward the upper sodium end of your range.
From 30km
Hold the schedule. Humid races punish a plan that relies on feel.
Frequently asked questions
How does humidity change marathon fuelling?
Humid air slows sweat evaporation, so you sweat more for less cooling. Fluid and sodium losses rise, heart rate drifts at the same pace, and perceived effort climbs. Plan higher sodium intake and keep carbohydrate steady rather than reactive.
How much sodium do I need in a humid marathon?
Many runners need 500 to 1,000mg per hour in humid conditions, though the correct figure depends on your measured sweat rate and how salty your sweat is. HYDRAX CORE provides 980mg of sodium per serve.
Should I drink to thirst in Brisbane?
Thirst is a reasonable guide in mild conditions but underestimates losses in humidity. Measure your sweat rate in similar conditions and drink to a plan that includes sodium, not plain water alone.
What should I eat before the Brisbane Marathon?
A familiar high-carbohydrate low-fibre breakfast around 3 hours out at 1 to 2g of carbohydrate per kg, then a pre-race serve 25 to 40 minutes before the start.
Keep reading
- Marathon fuelling strategy
- Carbs per hour for a marathon
- Carb loading for race day
- Running pace calculator
- Measure your sweat rate
- Shop the HYDRAX kit
Disclaimer: This page is general information for healthy adult athletes and is not medical, dietetic or coaching advice. Individual carbohydrate, fluid and sodium requirements vary with body weight, sweat rate, conditions and health status. Speak with your doctor, sports physician or an accredited sports dietitian before changing your nutrition or supplement routine, rehearse any fuelling plan in training before race day, and always follow the directions and warnings on the product label.