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Jack Davis

Paris Marathon

2nd April, 2023
France
Paris
strava
Running, Marathon - 42.2km
7°C
, Mild
3hrs 1min
more race details

Jack's headline numbers

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?
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~70
g
Carb per hour
Recommended 75g/h
~331
ml
Fluid per hour
Recommended 100-500ml/h
~1,250
mg
Sodium per litre
Recommended 800-1200mg/L
~2.5
mg
Caffeine per kg
Recommended 3-6mg/kg

Jack's strategy

Fueling

Carbohydrate is the main fuel you burn when racing. Failing to fuel properly is a leading cause of underperformance in longer races.

Carb-rich meal
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T - 1-4hrs: Ate a carb rich meal (Low in fat & fibre)
pre-fueled
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T - 15mins: Took in a final dose of carb
Carb per hour
Recommended 75g/h
~70
g
Jack's Energy Rating
9
/10
"I felt muscle fatigue was my main limiting factor towards the end of the race."
Our thoughts

Jack began the race fully stocked on glycogen after a strong carb-load in the 48 hours prior. He started race morning with a small amount of honey on a freshly baked French baguette. Within the final 30 minutes, Jack had a final pre-race gel, the timing of which is something Jack has refined by using a continuous glucose monitor. He found optimal increases in blood glucose occurred between 15-25 minutes after intake, so chose to utilise this for the race. His fueling strategy during the race was simple, taking 30 grams of carb every 25-30 minutes. To do this, Jack sipped on a PF 90 Gel in the first half, then consumed two PF 30 Caffeine Gels and a PF 30 Gel in the latter half.

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.

Jack1023mg/L
Jack has been Sweat Tested to dial in his 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.

Whilst Jack’s losses are on the moderate side, getting his hydration strategy right is still important if he wants to perform at his best.

Learn more
Pre-loaded electrolytes
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T - 60mins: Drank ~500ml of strong electrolyte drink
Fluid per hour
Recommended 100-500ml/h
~331
ml
Sodium per litre
Recommended 800-1200mg/L
~1,250
mg
Jack's Hydration Rating
10
/10
"Super happy with it!"
Our thoughts

During the race, Jack regularly picked up plain water from the aid stations, which he estimated to total ~1L across the race. To ensure he replaced a good proportion of his electrolyte losses alongside this, Jack carried Electrolyte Capsules with him, taking five throughout the race. This meant the relative sodium concentration of his intake was slightly above his sweat sodium concentration as measured by a Sweat Test, so he effectively replaced his sweat sodium and fluid losses.

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.

Pre-caffeinated
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T - 0-4hrs: Had a final hit of caffeine
Caffeine per kg
Recommended 3-6mg/kg
~2.5
mg
Our thoughts

Jack’s caffeine intake was slightly below the recommended scientific guidelines to achieve maximal performance benefit. At ~2.5mg/kg, he would still have seen a reduction in perceived effort, but could consider swapping his final pre-race gel out for a caffeinated version. Despite this, he managed to keep his perception of energy high and felt good throughout.

How Jack hit his numbers

Here's everything that Jack ate and drank on the day...

Jack's weapons of choice

Final thoughts

Jack's Satisfaction Rating
9
/10
My fuel and hydration plan felt spot on, muscle fatigue was my main limitation towards the end but overall I'm happy.
Jack
Overall, Jack’s first-ever standalone marathon went very much to plan, with only his time slightly falling below what he’d hoped. From a fueling and hydration perspective, Jack should take great confidence in how well he executed his plan and may look to reproduce it in similar events with tiny refinements to his caffeine intake whilst making sure he adapts this strategy to the conditions he faces in future events.
PF&H

Jack's full stats

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Overall
210g total carb
70g per hour
1,000ml total fluid
331ml per hour
1,250mg total sodium
414mg per hour
1,250mg
Sodium per litre
200mg total caffeine
2.5mg per kg

Data Confidence
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We rate each of our case studies from 1-5 based on the level of accuracy, and our confidence in the data.
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2
3
4
5

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).

Jack's recent case studies

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