In October 2015, I raced the Ironman World Championship in Kona for the third time. My finishing time was 10:31, nearly an hour slower than my 9:40 at Kona two years earlier.
I had a bad day. But "I had a bad day" is the laziest race debrief in endurance sports. It explains nothing. It teaches nothing. It guarantees you'll have the same bad day again.
What actually broke me at Kona 2015 was a compound failure mode that I hadn't planned for, that I didn't understand until months later, and that applies to any athlete who lives at altitude and races at sea level in the heat.
The Setup
In August 2015, two months before Kona, I moved from the San Francisco Bay Area to Boulder, Colorado. Elevation: 1,600 meters (5,430 feet). I'd lived at sea level or near it my entire racing career. The move to Boulder was for lifestyle reasons, not altitude training. But I assumed it would help, because "altitude training" is supposed to be good for endurance athletes, right?
My fitness numbers coming into Kona were solid. Not peak-year numbers, but certainly good enough for a strong race. I'd done my Kona heat prep: sauna sessions, hot rides. I'd been to Kona twice before. I knew the course, knew the conditions, knew the competition.
What I didn't know was that the interaction between altitude acclimatization and heat racing creates a specific physiological conflict that neither altitude training nor heat training alone can address.
The Physiology
Here's what happens when you live at altitude. Your body adapts to the lower oxygen availability by producing more red blood cells. More red cells means more oxygen-carrying capacity. This is the "altitude benefit" that endurance athletes chase.
But there's a less-discussed side effect. To produce more red blood cells, your body reduces plasma volume. Plasma is the liquid portion of your blood. Less plasma means thicker, more viscous blood. At altitude, this is fine because the extra red cells more than compensate for the reduced plasma volume. Net effect: better oxygen delivery at altitude.
Now descend to sea level for a race. Your red cell mass stays elevated (good), but your plasma volume is still reduced (bad). At sea level, where oxygen availability is no longer the limiting factor, the reduced plasma volume becomes the dominant constraint.
Why? Because plasma is how your body cools itself.
When you exercise in heat, your cardiovascular system has to do two jobs simultaneously: deliver oxygen to working muscles and deliver blood to the skin for cooling. Plasma volume is the key resource for both jobs. More plasma means your body can send blood to the skin for cooling while maintaining adequate blood flow to the muscles. Less plasma means it has to choose: cool or perform.
When an athlete descends from altitude to race in Hawaiian heat, they arrive with the worst possible combination: elevated red cells they don't need (sea-level oxygen is plenty) and reduced plasma that they desperately need for cooling. Their body is adapted for an environment that no longer exists.
Heat Prep at Altitude Doesn't Fix It
The standard heat prep protocol works by expanding plasma volume. Sauna sessions, hot rides, hot runs. These stimuli cause the body to produce more plasma to support the increased cooling demand. Over 10-14 days, plasma volume increases and the athlete becomes more heat-tolerant.
I did heat prep at altitude. Sauna sessions in Boulder. Hot rides when I could find them. The problem is that altitude itself is working against plasma expansion. The altitude stimulus is constantly signaling "reduce plasma, make more red cells." The heat prep stimulus is signaling "expand plasma for cooling."
These two signals compete. At sea level, heat prep wins easily because there's no altitude signal. At 1,600 meters, the altitude signal is persistent and strong. My heat prep was probably less effective than it would have been at sea level because my body was simultaneously fighting the plasma expansion I was trying to create.
I didn't know any of this going into the race. I'd done my heat prep. I'd ticked the box. I assumed I was adapted.
Race Day
The swim was fine. The bike was controlled. I got to the run feeling like I was in reasonable shape.
Then the heat hit. By mile 6, I was overheating. By mile 10, I was in real trouble. My heart rate was elevated not from effort but from thermoregulatory strain. I could feel my body choosing between cooling and performance, and cooling was losing.
The run fell apart. I slowed. I walked. What should have been a 3:15-3:25 marathon became something much worse. The final time was 10:31.
The Compound Failure Mode
After the race, I spent weeks trying to understand what happened. The heat was real, but I'd raced Kona in heat before and managed it. My fitness was adequate. My nutrition was standard. Nothing obvious had gone wrong.
It wasn't until I started reading the physiology literature on altitude-descent athletes in heat that the picture came into focus. The interaction between reduced plasma volume from altitude acclimatization and increased cooling demand from Hawaiian heat created a physiological conflict that my heat prep hadn't resolved.
This is what I mean by a compound failure mode. It's not one thing going wrong. It's two factors that are individually manageable but together create a problem that's worse than either one alone. I'd prepared for heat. I'd adapted to altitude. But I hadn't prepared for the interaction between altitude adaptation and heat racing.
Per-Athlete Recurring Fault Catalogs
Kona 2015 taught me that every athlete has fault modes that are specific to them, and that the most dangerous ones are compound interactions that don't show up in standard preparation checklists.
My fault modes include: glute cramping under sustained high-power bike efforts (Kona 2013), GI failure under extreme dehydration (Cozumel 2012), and altitude-heat interaction (Kona 2015). None of these are universal. Other athletes have completely different fault modes.
The fix isn't a generic checklist. It's a per-athlete catalog of known failure modes, each with a specific prevention protocol and a detection protocol for race day.
For the altitude-heat interaction specifically, my protocol is now: if I'm living above 1,200 meters and racing at sea level in heat, I descend 10-14 days early and do my heat prep at sea level. The descent allows plasma volume to re-expand naturally, and the heat prep at sea level isn't competing with the altitude signal.
It's a simple fix once you understand the mechanism. But understanding the mechanism required having the failure, doing the debrief, and finding the physiology. "I had a bad day at Kona" wouldn't have produced any of that understanding.
The Framework Lesson
Every bad race has a mechanism. Finding it requires a real debrief, not "I had a bad day" or "it was hot" or "I didn't have it today." Those are descriptions, not explanations.
The debrief framework I use now is: what broke? When did it break? What was the proximate cause? What was the underlying cause? Is this cause per-athlete (specific to my physiology) or generic (would affect any athlete)? Has it happened before? If so, what's the pattern?
Kona 2015 broke me because I lived at altitude, raced at sea level in heat, and didn't understand the physiological interaction between those two factors. It's a per-athlete failure mode because not every athlete lives at altitude. It hadn't happened before because I'd never lived at altitude before racing Kona.
Once I understood the mechanism, the fix was straightforward. Descend early. Heat prep at sea level. Problem solved.
But the problem only got solved because I refused to accept "bad day" as an explanation and kept digging until I found the mechanism. That's the debrief discipline. It's not fun. It's not glamorous. But it's how you turn a 10:31 into knowledge that prevents the next 10:31.
Want to work with me? I coach athletes from first-time Ironman to Ultraman.