In our last post we looked at heat training and why it's become one of the most talked-about tools in endurance sport. But heat adaptation is only half the equation. Get in the heat without a proper hydration strategy and you're not building fitness you're just digging a hole.
Why "Drink More Water" Isn't a Strategy
Most triathletes know they sweat more in summer. Few know how much, or what's actually in that sweat. Water alone doesn't cut it sodium loss is the bigger problem for most athletes, and replacing fluid without electrolytes can leave you feeling worse, not better, despite drinking plenty.
Step 1: Know Your Sweat Rate
A sweat rate test is simple and takes one session:
- Weigh yourself & bottles (naked, pre-session)
- Complete a 60-minute session at typical race intensity, tracking fluid intake
- Weigh yourself again (with empty bottles) post-session
- Sweat rate (litres/hour) = (pre-weight − post-weight)
Do this in both cool and hot conditions the difference is often significant, and it's the single biggest variable in getting your race-day plan right.
Step 2: Understand Your Sodium Loss
Sweat sodium concentration varies enormously between athletes — from under 500mg/litre to over 1500mg/litre. "Salty sweaters" (visible white marks on kit, stinging eyes, cramping in hot races) typically sit at the higher end and need considerably more sodium replacement than generic sports drink guidelines suggest. This is exactly where products like Precision Fuel & Hydration one of our partners are useful, offering sweat testing and electrolyte formulations tailored to the individual rather than a one-size-fits-all approach.
Step 3: Build a Session-by-Session Plan
Once you know your numbers, hydration stops being guesswork:
- Training: match intake to sweat rate for sessions over 60-90 minutes, adjusting for heat and humidity
- Race day: plan sodium and fluid intake per hour based on expected conditions, not just what you did in training six weeks ago in cooler weather
- Practice it: never try a new hydration strategy on race day rehearse it in key long sessions first
Step 4: Don't Forget Post-Session Recovery
Rehydration doesn't stop when you finish. Replacing 100-150% of fluid lost (accounting for ongoing sweat losses) alongside sodium in the hours after a session speeds recovery and prepares you for the next day's training particularly important during a heavy summer training block.
Putting It Together
Heat training earns its reputation as a performance tool only when paired with a hydration strategy built on your own numbers, not generic advice. If you're heading into IRONMAN or an autumn 70.3 and want your fuelling and hydration dialled in properly, this is exactly the kind of detail we work through with athletes in our 1-2-1 coaching. You can also find like-minded athletes swapping tips on exactly this in the OE Club.
Got questions about your own hydration strategy? Get in touch for a free consultation.
Thanks Coach Ross