Lauren Hall
Valencia Marathon
ValenciaTop 50, FPROLauren's headline numbers
Lauren's strategy
Fueling
T - 1-4hrs: Ate a carb rich meal (Low in fat & fibre)
T - 15mins: Took in a final dose of carb
"I felt a bit sick after taking my fifth gel. Then after the race I felt quite queasy until late in the evening"
Lauren executed an improved fueling strategy, consuming ~76g/h of carbohydrate across the marathon by taking eight single-source carbohydrate gels spaced out every 5km. Lauren experienced some GI discomfort from around the 5th gel onwards, with nausea lingering until the evening. This is common when consuming high rates of single-source carbohydrates, as the gut's glucose transporters can become saturated. Lauren will continue gut training and transition to dual-source carbohydrates in 2026, allowing her to benefit from multiple sources of carbohydrate which can increase carbohydrate oxidation of external (ingested) carbohydrates and delay the use of muscle glyogen, which improves running economy and may enhance performance.
Hydration
Taking on board an appropriate amount of fluid and sodium is essential to maintaining blood volume and supporting the cardiovascular effort needed to perform on race day.
Whilst the absolute amount of sodium and fluid consumed per hour is important, it’s critical to consider these in relation to each other. This is known as 'relative sodium concentration' and it’s expressed in milligrams per litre (mg/L). How much sodium you’re taking in per litre of fluid is more important than the absolute amount taken in per hour.
Lauren1308mg/L
Lauren has been Sweat Tested to dial in her hydration plan
Sweat sodium concentration (mg/L) is largely genetically determined and remains relatively stable. Knowing how salty your sweat is enables you to replace a good proportion of your sweat losses, which can range from 200-2,000mg/L.
Given Lauren's losses are High (1,308mg/L), nailing her hydration strategy remains important, even when it's Mild.
Learn moreT - 60mins: Drank ~500ml of strong electrolyte drink
"I almost felt overhydrated for the first 10-15km, where I felt a small stitch and heavy. This eased off during the remainder"
During the race, she kept fluid intake modest at ~232ml/h, which was appropriate for the mild Valencia conditions and relatively “short” race. She supplemented with two PH Electrolyte Capsules, one at 45 and another at 90 minutes, achieving a relative sodium concentration of 892mg/L - a decent match for her high sweat sodium losses, without over- or under-doing it.
Lauren experienced a mild calf twinge between 20-30km, which resolved after backing off the pace slightly. In hindsight, she felt a little over-hydrated early on, and pouring a full bottle of water over herself at one aid station left her feeling heavy from being covered in water. For future races, she'll look to be more conservative when pouring fluid on her clothes to avoid that heavy feeling. She’ll also play around in training with her pre-race hydration strategy to allow her to settle more easily into the opening kilometres without feeling as full.
**Heat training**
After a tough time in the Manchester Marathon during some warm weather eight months prior, Lauren completed nine sessions of heat training at the Precision Performance Lab ahead of Valencia, supplemented with hot baths between active sessions. She saw a 12% increase in running speed relative to her heart rate, while her within-session performance drop-off reduced from 18% to just 6% - meaning she could run for an hour at 39°C with minimal cardiovascular drift. This adaptation left her well-prepared for the conditions race day could have delivered.
Caffeine
Beyond the Three Levers of Performance (carb, sodium and fluid), caffeine is one of only a few substances that is proven to improve performance for most endurance athletes as it can help stave off mental and physical fatigue.
T - 0-4hrs: Had a final hit of caffeine
Lauren used three-quarters of a caffeine gum pre-race (~75mg), which helped with the early morning start. Lauren felt very alert during warm-up - perhaps a little too alert initially - but was glad she took the dosage as the race progressed. At just ~1.5mg per kilogram of her bodyweight, there's likely room to increase her caffeine intake in future races to more closely align with the recommendations. This would involve Lauren building towards ~4mg/kg with some practice in training and smaller ‘B races’, perhaps using PF 30 Caffeine Gels to deliver a larger caffeine boost *during* the marathon.
How Lauren hit her numbers
Here's everything that Lauren ate and drank on the day...
Final thoughts
“Great solid effort on nutrition and hydration, but I am so keen to improve and listen to recommendations.”
“This was an excellent execution from Lauren - a 2:35:30 marathon with strong energy levels and a well-dialled sodium strategy. The GI discomfort highlights an opportunity to transition to dual-source carbohydrates, to increase absorption rates and reduce gut stress as she exceeds the typical 60g/h limit for single-source carb absorption. Looking ahead, Lauren's focus for 2026 will be to transition to dual-source gels, finessing her pre-race hydration strategy to hit those first kilometres comfortably, and building her caffeine use up to maximally reap the benefits. With these tweaks, she's well-positioned to go even faster next time.”
PF&HLauren's full stats
Data Confidence
We rate each of our case studies from 1-5 based on the level of accuracy, and our confidence in the data.
There is good confidence in the accuracy of the data reported. An athlete feels that the numbers closely reflect what they consumed despite a couple of estimations which may carry some degree of error. The majority of what was consumed is recorded to a high level of specificity (most volumes are known through the use of bottles brands quantities flavours). The numbers are very plausible and align with previous data recordings (if an athlete has collected data previously).