Chicago Marathon

Izzi's fueling started two days out with a structured carb load as she consumed ~610g of carb on Friday and ~605g on Saturday. That's ~11g of carb per kilo of bodyweight each day, which is nicely within the 8-12g/kg range that the research suggests athletes should aim for to maximise muscle glycogen stores before a marathon. She chose to eat familiar, low-fibre, low-fat foods like white rice, pasta, oats, bagels and rice cereal. She spread her intake across the day and topped it up with simple sugars from honey and sweets.

On race morning, she got ~121g of carb from a bagel, honey and instant oats at 5am, which meant she ate (~2.2 g/kg about two hours before the start). This falls nicely within the recommended range for a final pre-race meal of 1-4g/kg in the 1-4 hours before race start. She continued to fuel with a PF 30 Chew at 6:55am and a [PF 30 Caffeine Gel]() on the start line. That's ~180g of carb before the gun, which tops up liver glycogen which becomes depleted while you sleep overnight, without leaving her feeling heavy.

During the race, Izzi averaged ~119g of carb per hour from eight bottles of PF Carb & Electrolyte Drink Mix and PF Carb Only Drink Mix at pro aid stations, plus two caffeine gels. Few athletes can absorb carbs that fast while running at a pace that saw her break the Australian marathon record, especially in warm, humid conditions. In the heat, blood flow is diverted away from the gut towards the skin and working muscles, which makes stomach issues more likely. Izzi felt some slight discomfort after 10km, and choosing to back off to a few sips of her bottle at 15km was a smart call. She still took her PF 30 Caffeine Gel at that point, so her carb intake didn't drop, and the discomfort passed quickly. Being able to settle and get straight back on plan is a clear sign of a well-trained gut.

High exercise intensities, such as a 2:20 marathon pace, can push sweat rates up by at least 50%, making it challenging to compensate adequately for these losses. Izzi got ahead of this by preloading with a PH 1500 tablet on Saturday evening and another on race morning, so she started well hydrated.

During the race, she averaged ~719ml of fluid per hour with a relative sodium concentration of ~869mg per litre. That's a solid intake for a marathon at such an intensity and nearly double what she has previously consumed when racing, but suitable here, where she would have been replacing a greater proportion of her losses and maintained a more balanced hydration status. Mixing 200ml bottles of Carb & Electrolyte Drink Mix with Carb Only Drink Mix allowed her to keep consuming sodium at the correct rate for her losses with additional carbs. Pouring water over herself every 2.5km was a big part of her day too. External cooling like this lowers skin temperature and can reduce how hard the effort feels when generating a significant amount of heat due to muscular contraction, helping you hold pace for longer. It also saves the fluid in your bottles for drinking, rather than using it to cool down.