IRONMAN 70.3® Swansea

Benji’s bike leg was the strongest part of his fueling day. He took in ~96g/h on the bike, comfortably at the ~90g/h we’d target for a middle distance race at his effort level, with the majority of it coming from PF 300 Flow Gel decanted into a top tube flask. That format really suited a course like Swansea. With the punchy climbs, Benji rode the course “almost like an interval session”, and having a flask he could sip from without unwrapping anything let him fuel whenever the terrain allowed rather than sticking to a fixed clock. A PF 30 Chew and a first hit of Flow Gel out of T1 got him started, and a GI rating of 8/10 at that rate of intake suggests his gut coped with it well.
His carb intake then fell to ~48g/h on the run. Some drop-off between disciplines is normal and expected - fuel is harder to carry and swallow when running, and blood flow is diverted away from the gut - but halving his bike rate is a big step down. Holding ~96g/h on the bike with minor GI niggles suggests there’s real headroom to lift the run leg toward 60-70g/h. Practically, that’s one or two more PF 30 Gels spread across the half marathon, or a small flask of Flow Gel carried out of T2. With a full-distance race later this year, this is the single highest-value thing to work on: with the run leg doubling, the cost of under-fueling is greater. Building run-specific gut training into his long runs now is the way to handle the extra fueling on race day.

Benji set himself up well before the gun, taking a PH 1500 tablet in 500ml of water, which is a sensible sodium preload to expand plasma volume and start the swim properly hydrated. On the bike, he had an intentionally simple setup: PH 1000 (Sachets) in everything, two 1L bottles on board plus two 750ml pick-ups on course. That gave him just over 1L/h of fluid at a relative sodium concentration of ~1,000mg/L - within ~60mg/L of his measured sweat sodium concentration. Drinking to the top of the 500ml-1L/h range was the right call in that humidity, and replacing sodium at close to the rate he loses it supports fluid retention and the blood volume needed for thermoregulation. On the run, his fluid intake dropped just below the ~502ml/h we typically see on average across middle distance runs in our case study database - whilst sodium climbed, because of three 250mg Electrolyte Capsules alongside mostly on-course PH 1000 (Tablets). The result was a relative sodium concentration of ~1,500mg/L during the run leg, roughly 1.6x his own sweat sodium concentration. Over a 1:55 half marathon, that isn’t a problem, and his 10/10 rating for hydration backs that up. However, going so high for the full distance isn’t recommended. Benji could carry a refillable soft flask so he can top up at aid stations, which would let him drink more and keep track of the overall volume to nail that sodium concentration over the full distance.