North Coast 500 FKT

Setting a new female Fastest Known Time (FKT) on the North Coast 500 required Caroline to fuel effectively across more than 32 hours of continuous cycling through the Scottish Highlands, a challenge that demands a very different nutritional approach to shorter events. Rather than relying predominantly on sports nutrition products, she leaned heavily on real food, with homemade flapjacks, rice pudding, bananas and Snickers bars forming the backbone of her intake, alongside some PF 30 Chews, a combination well suited to the palatability demands of ultra-endurance racing. Ahead of the attempt, Caroline visited the Precision Performance Lab for a lactate threshold test, which allowed us to build a power-keyed substrate oxidation model and estimate her carbohydrate and fat requirements for the specific intensities she would be sustaining on the NC500. She averaged ~48g of carbohydrate per hour across the full effort, a rate that closely matched her estimated carbohydrate oxidation of ~52g/h from that pre-event analysis, a strong result given the complexity of fueling across 32 hours. At the intensity Caroline sustained, predominantly in Zones 1 and 2, fat contributed around 60% of her total energy expenditure, meaning body fat stores did a significant amount of the heavy lifting; this is entirely expected and appropriate for events of this duration. Looking ahead, there may be value in slightly increasing carbohydrate intake during higher-intensity sections, such as climbs or the earlier hours of the ride, to help spare glycogen and support pace when it matters most.

Caroline raced in cool, damp Scottish conditions averaging ~11°C with high humidity, which kept sweat losses well below what they would be in warmer weather. Her fluid intake averaged ~380ml/h across the 32 hours, a volume well matched to the conditions and one that would have limited the risk of accumulating a performance-impairing level of dehydration. She hydrated primarily with a combination of PH 500 and PH 1000 tablets across the three segments, which produced a relative sodium concentration of ~888mg of sodium per litre of fluid across the FKT, modestly above her sweat sodium concentration of 757mg/L. This proactive approach to sodium replacement is sensible over such a long effort, where even small hourly deficits can accumulate into a meaningful shortfall. A practical refinement for future attempts would be to track fluid distribution across the event more consistently, since the data shows a notably lower intake during the first early stages of the ride compared to later sections, albeit this may reflect the cool early-morning start. Ensuring more even access to fluids throughout would further reduce the risk of any localised under-drinking.

Caroline consumed a total of 743mg of caffeine (~11.8mg of caffeine per kilogram of bodyweight), which was relatively well distributed across the ride, and came primarily from caffeine and taurine gummies. While this total exceeds the commonly cited 3-6mg/kg performance guideline, the drip-feed approach taken over 32 hours is a well-considered strategy for ultra-endurance events, where the goal is to maintain circulating caffeine at effective blood concentrations rather than to achieve a single ergogenic peak. Given the duration and the particular challenge of managing alertness through the night hours, this level of intake is appropriate and consistent with the high habitual caffeine tolerance many ultra-endurance athletes develop.