IRONMAN® World Championship

Kona pushes your body to burn carbohydrates faster than almost anywhere else. A 2025 meta-analysis of 51 studies found that *both* carbohydrate oxidation and muscle glycogen use are significantly higher during prolonged exercise in hot conditions than in temperate ones, and that the effect is amplified further when you're dehydrated in the heat. In other words, what you take on during the race matters even more on the Big Island than it does at a cooler race. Kellie did this well and averaged ~85g/h of carbohydrate across the day, putting her close to the recommendations of 90g/h. Taking some fuel in the last 30 minues before the race start might support her energy levels better.

Kellie’s bike intake, ~109g/h, was greater than her run and came from a combination of concentrated Carb & Electrolyte Drink Mix, PF 300 Flow Gel, PF 30 Chews and PF 30 Caffeine Gels. Research has shown that taking 120g/h of combined glucose and fructose increases the amount of carbohydrate you can burn from what you eat compared with 90g/h, so pushing beyond 90g/h on the bike as Kellie did here is supported by current literature. On the run her intake dropped to ~75g/h. That's a very common pattern executed by triathletes, as running jostles the gut far more than cycling so Gi tolerance is often lower. Kellie's energy dip in the final quarter of the marathon lines up with when she stopped consuming gels and switched to cola late in the marathon, but is probably more a result of being 10 hours into a demanding race. Maintaining her run intake closer to 90g/h, for example by carrying a PF 300 Flow Gel in flasks, that she can sip between aid stations, looks like the clearest opportunity next time to bring her intake and energy up.

Kellie went into the race with a fairly dialed hydration plan, after a week spent in the hot and sweaty Precision Performance Lab. With a sweat sodium concentration of 778mg/L, the relative sodium concentration of her intake was well-matched, with 815mg/L on the bike and 825mg/L on the run. Most of that came from on-course PH 1000. Sodium in your drinks doesn't fully protect you from hyponatremia, but matching what you lose in sweat greatly reduces how much you dilute your blood. Her frequent need to pee on the bike tells us she was likely drinking at or slightly above her sweat losses, and it wasn’t a sodium related issue, and with pre and post-racae bpdy mass measurements, Kellie's level of dehydration was within the acceptable range.

The dry mouth she experienced during the race was likely a result of heavy breathing into a hot headwind, salt water from the swim, and sticky concentrated fuels without fluid. A small swig of plain water after concentrated carbs can ease that sensation without adding much volume. On the run, despite estimated sweat rates being higher, her fluid intake almost halved to 833ml/h since she frontloaded her intake on the bike. Her handheld flask was loaded with a PH 1500 and refilled with PH 1000 at every other aid station. It was a smart way to keep both electrolytes and fluid consistent throughout.