Field note · June 10, 2023 · 2023 · June, week 1 · 3 min read · by Jay
Heat is the fourth sport
In Honolulu the humidity decides how hard a session is, whatever the plan says.
Why humidity is the whole story
We live here, and we still get it wrong, which should tell you something about how it goes for visitors. Heat by itself is a number on a forecast, and it's the humidity that decides whether your body can do anything about it. Sweat cools you by evaporating, and when the air is already full of water it doesn't evaporate, it just runs down your arms and into your shoes, so you're losing the fluid and getting none of the cooling for it. What that means in practice is that an effort that felt easy in dry air feels hard here at the same pace, and your heart rate climbs through a long session even when nothing else changes. That drift has nothing to do with how fit you are, and pretending it isn't happening is how people end up in trouble at mile nine of a half that started at 5:30 in the morning. So the number we look at is the humidity, before the temperature, and when it's up, which is most of the summer here, every session is a heat session whether the plan calls it one or not.
Dawn is a temperature
Every long workout we do starts in the dark, because dawn is the only hour the work can happen here, and discipline has less to do with it than it looks. By 8 a.m. the pavement is already hot, by 10 the shade is gone, and a long run that starts at 7 finishes in much hotter conditions than the ones it started in. The local races know this, which is why the Honolulu Marathon starts at 5 a.m. and Hibiscus starts early, and why Honu in June starts with a swim at first light and then sends you into the lava fields for a bike ride with no trees and no shade. So the alarm is early, and everything else in the week follows from that.
Water and salt
We don't sell electrolytes and we're not going to recommend a brand, but we can tell you what we usually do, which is drink before the session, carry more water than seems reasonable, and put salt on real food in the days around a long effort. In this humidity the sweat rate is high and the sweat is salty, and a long day without replacing both of those ends badly. What we actually carry, since the story of how we learned about salt is on the brick note, is salt tablets and a sodium-heavy electrolyte drink, on any session over a couple of hours and on every race. We've used several brands and the point is the sodium, so the label doesn't matter much and we don't name one. On a hot long ride we stop for water more often than the plan says, on a long run we carry it, and on race day we hit every aid station from the first one whether we feel like it or not, because by the time you feel like you need it you're already behind.
What a mainland plan gets wrong here
Any plan written somewhere cool assumes your body can cool itself, and here it can't, so a few things follow. Paces are slower for the same effort, and slower is the correct answer here, long sessions have to start earlier and end sooner than the plan thinks, and recovery takes longer because the body worked harder than the pace suggests. Every race is a heat race, including the ones in what the calendar calls winter. We adjust a plan with the alarm clock and the humidity, and we've never found a formula that does it better.
Honu, if you want proof
My first 70.3, in June 2023, is this whole note in one race. I swam at first light in the ocean, then rode 56 miles through black lava with the wind coming off the water and not a tree for miles, and then ran a half marathon in the heat of the day. The people who finished well were the ones who respected the heat from the first pedal stroke, and the ones who didn't were walking by mile four of the run. The race report's here.