By Scott Fenwick
Editor’s note: In the marathon, air temperatures above 15°C/59°F can slow you down. While heat training is the best way to prepare for warm conditions, we asked Scott Fenwick of Kanizsa Coaching to share additional tips for staying cool on race day.
You know that feeling when your brain melts like soft-serve ice cream, the road flips to lava mode, and you're sweating so much your shadow might slip in your own puddles? Here are tips on how to race (and prepare) when the heat is on.
The principles
- Skin ≠ core. Your skin surface temperature is not the same as your core inner temperature. They're linked, but your primary goal is controlling your core temperature.
- Outer changes fast; core changes slow. Skin temperature can fluctuate quickly. Core temperature rises more slowly— however it falls more slowly too.
- Work makes heat. Muscles generate heat; more intensity = more heat. Reduce core overheating and you'll race stronger.
Overall approach
- Stay cool as long as possible. Prevent heat from accumulating early—this pays off later.
- Prioritise evaporation. Sweat (and water you pour on) that evaporates is your biggest heat sink while moving.
We all know this instinctively: a cold shower chills your skin immediately, but your core barely budges at first. Sustained mild cooling, however, can shift or manage core temperature meaningfully.
Preparation for a warm weather marathon - start well before race day
Heat Adaptation
- Heat training can be one of the most impactful ways to stay cool. The tools provided by CORE not only allow you to understand your body's temperature real-time during an event; a crucial feature is using these tools proactively to train heat adaptation ahead of an event. As a general target, aim to get your Heat Adaptation Score greater than 80% by the week before the race.
Clothing
- Get your kit wet—on purpose. If you'll be dousing yourself or sweating heavily, practice in your race kit. Wet fabric can chafe; solve it early with anti-chafing products or a different kit choice. This can also be the case for run-showers as your shoes and socks will get wet.
- Lightweight, run-specific kit is generally designed to allow air to circulate freely between the body and fabric. However, some items such as sports bras or lycra-based run shorts are made to fit more snugly and provide support. Practice with various options to find what works best for you.
- Headwear: practise with any visor/cap or headband. Race-expo specials are tempting—don't debut them on race day.
- Fabrics & tech: Thermoregulation fabrics are evolving (some are genuinely fascinating ) and read like science fiction - carbon nanotube coatings as dynamic textile for example! High tech is costly. It can add a marginal but worthwhile advantage for some. However, the basics are free and significant.
Sun cream
- Train with the same sunscreen you'll race in—especially on the face. Ensure it won't run/sting into eyes.
Hydration
- Aim for sensible, steady hydration across race week—especially in hotter climates or if you're spending time in air conditioning. It's not about guzzling liquids on race morning.
Nutrition
- Rehearse your race nutrition. GI issues can be worse in heat. Dial in products, timing, and amounts for heat specific conditions.
Practicalities
- Practise toilet detours in wet kit. Wet kit behaves differently—know how to pull on/off items efficiently and without damage.
On the day when racing in warm environments
Keep cool early
- The body takes time to heat up internally. You might feel hot while your core is still fine. Once core temp climbs, it's hard to lower while moving, so your strategy is to delay that rise:
- Morning of: wear lightweight layers, seek shade, move calmly. Opt for relaxed mobilisation, not a hard, sweaty warm-up. Be the most chilled.
- Fluids: start early and steady.
- Water for cooling: pour on skin/kit to promote evaporation.
- Find shade when the course allows.
Pacing & mindset
- Adjust pace early to the conditions. Avoid the "too hot too soon" trap.
- Build your pace through the race. Keep the mantra: "Stay as cool as possible for as long as possible."
- Rather than chasing the static data of cool weather splits, adapt dynamically to the environment of the actual event. Tools such as the CORE Heat Strain Index or simple internal body temperature allow you to monitor your body's reaction to the event demands in real-time and stay below a pre-determined threshold.
- For those without access to a CORE sensor, or in addition, you can use RPE and HR limits. However, if temperature is the main limiting factor, then optimising to the heat constraint makes most sense.
- It's a long race, be willing to walk briefly (strategically) if needed for cooling and HR control. Short, early resets can protect the overall average pace far better than an overheating blow-up.
Nutrition under heat stress
- Blood is juggling between (i) working muscles, (ii) heat distribution, (iii) digestion. Cooling demands can influence GI throughput. This is where that pre-race practising can really benefit.
- Separate hydration and energy inputs. This allows you to keep yourself hydrated but not take on too much GI loading
- Use time alerts to stay on schedule. If you slip, don't try to "catch up" all at once—resume plan gradually.
Enjoy it (seriously)
Everyone's feeling the heat. With smart tactics, you get the edge—cooler head, stronger finish.
Further reading : there are lots of interesting posts and papers linked from CORE's blog and educational resources. Keep your plan simple: cool early and keep stay cool as long as possible.
About The Author
Scott Fenwick, triathlon and multisport endurance coach. International clients in US, UK, France and Switzerland. Qualification via British Triathlon and La Fédération Française de Triathlon. Kanizsa Coaching and Substack.