The 13.5/1.5 Was a Cooling Protocol Disguised as a Pacing Protocol

I won a three-day, 320-mile ultra in 30-degree Hawaiian heat without ever crossing the hyperthermia threshold. My peak core temperature across 19.4 hours of racing was 38.1 degrees Celsius. Time above 38.5 (the threshold where your central nervous system starts to shut down): zero percent.

For context, competitive Ironman runners in Hawaiian heat regularly cross 39 degrees. At 40 degrees you get the death-march walk you see in Kona finish-line videos. I was running an elite thermoregulatory baseline while racing for the win.

The reason wasn't genetics or heat tolerance. It was a pacing protocol that was secretly doing two jobs at once.

The Protocol

For Day 3 of Ultraman 2017, the 52.4-mile double marathon, my race plan specified the 13.5/1.5 protocol: 13.5 minutes of running at 8:03 per mile, followed by 1.5 minutes of walking. Repeat for 7 hours.

The pacing math is straightforward. 13.5 minutes of running and 1.5 minutes of walking in every 15-minute block produces an effective pace of about 8:55 per mile when you account for the walk breaks. Over 52.4 miles, that's roughly a 7:01 finish. I actually finished Day 3 in 7:04, averaging 8:12 per mile on the run segments. Nine seconds of drift over 52 miles.

What makes this protocol interesting isn't the pacing. It's what happens during those 1.5-minute walk breaks.

The Walk Break Is a Cooling Intervention

Every walk break was a chance to drink ice water, pour ice down my suit, and let my body shed heat without the metabolic load of running. I wasn't just walking to rest my legs. I was walking to cool my core on a 15-minute cycle.

I know this because I had data. Before Day 1 and Day 3, I swallowed a Bodycap e-Celsius pill, an ingestible core-temperature sensor that logs your internal temperature every 30 seconds via Bluetooth. Direct physiological data on what's happening inside, not a proxy like skin temperature or heart rate.

The data told a story I didn't expect.

Day 1 vs Day 3

On Day 1 (the bike day after the swim), the core-temp curve shows long stretches at the upper envelope, 37.5 to 38 degrees, with occasional drops when I took on fluids. The pattern is irregular because on the bike you drink when you think of it, not on a fixed schedule.

On Day 3 (the run), the curve looks completely different. A dense, regular oscillation with downward spikes every few minutes. Those spikes are cold-fluid ingestion events. Every time I drank ice water or took on ice during a walk break, the pill registered cold stomach contents for about a minute before the fluid warmed to body temperature.

The 13.5/1.5 protocol was creating a forced cooling cycle. Every 15 minutes, like clockwork, my core temperature got pushed back down.

The result: Day 3 produced less thermal strain than Day 1 despite being longer, hotter (no swim-water cooling), and a run instead of a bike. The run should have been thermally worse. Less ambient airflow than the bike. More metabolic heat production per kilogram. Instead the cooling cadence beat the bike's natural airflow advantage.

Two Jobs at Once

Most race plans treat pacing, fueling, hydration, and cooling as four separate tracks. You have a pace target. You have a calorie-per-hour target. You have a fluid-per-hour target. You might have a "take ice at aid stations" note. Four parallel systems, each managed independently.

The 13.5/1.5 protocol collapsed these into one integrated structure. Every 15-minute cycle delivered:

Pacing. The run/walk ratio produces a predictable effective pace that I'd practiced until it was muscle memory. No decisions required.

Fueling. Walk breaks are when I took gels and solid food. Easier to eat while walking than running.

Hydration. Walk breaks are when I drank. Easier to drink without choking while walking.

Cooling. Cold fluid ingestion plus reduced metabolic output during the walk phase created a regular thermal reset.

One cadence. Four outputs. No cognitive load during the race, because the protocol runs itself once it's practiced enough.

Why This Matters for Your Racing

You don't need an ingestible temperature pill to apply this principle. The insight isn't about the data. It's about designing race protocols that serve multiple purposes simultaneously.

Most athletes I coach build their race plan as a pace chart with nutrition bolted on. The pacing is one thing, the fueling is another thing, and they try to remember both while racing. That's two cognitive tracks competing for attention in a brain that's already compromised by fatigue and heat.

A better approach: find the natural rhythm of your race and make it do multiple jobs. If you're doing run/walk intervals anyway, make the walk break your fueling window, your hydration window, and your cooling window. If you're doing a structured bike with power targets, align your eating schedule to the recovery valleys between efforts.

The fewer separate systems you're managing during a race, the more likely you are to execute all of them well. One integrated cadence beats four parallel tracks every time.

The Framework Lesson

Most race-plan failures aren't fitness failures. They're execution failures. And most execution failures happen because the athlete is trying to manage too many independent systems while cognitively impaired by fatigue, heat, or both.

The fix isn't more willpower. It's better protocol design. Find the structures that do two jobs at once. Practice them until they're automatic. Then trust the protocol on race day instead of trying to make real-time decisions with a compromised brain.

The 13.5/1.5 protocol wasn't just a pacing protocol. It was a cooling protocol disguised as a pacing protocol. Two jobs at once. That's not an accident. It's a design choice that gets validated by direct physiological data.

When you can find that kind of dual-purpose design in your own racing, grab it.