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Sam Skinner's scorecard

Arc of Attrition

Friday 27th January, 2023

Within recommended ranges

Just outside recommended ranges

Significantly outside recommended ranges

  • 87g

    Carb per hour
  • 343mg

    Sodium per hour
  • 313ml

    Fluid per hour
  • 1,098mg/L

    Relative sodium concentration
  • 20.83mg/kg

    Caffeine per bodyweight
  • How Sam hit those numbers

    450ml x PH 1500
    1 x PF 30 Chew
    300ml x Beetroot Juice
    1 x Porridge Pot
    500ml x Energy Drink Mix
    12 x PH Electrolyte Capsule
    1L x PF Energy Drink Mix
    2 x PF 30 Energy Gel
    4 x PF 30 Caffeine Gel
    5 x PF 30 Energy Chews
    750ml x Plain water
    6 x Energy gel (25g carb)
    2L x Energy drink mix (80g carb)
    1L x Energy drink mix with caffeine (80g carb, 100mg caffeine)
    2 x Energy gel (40g carb)
    2L x Coca Cola Original
    250ml x Black Coffee
    2 x Slices of Pizza
    6 x Energy bar (41g carb)
    0.5 x Noodle Pot
    7 x Flapjack Bite
    2 x Rice Pudding Pot
    2 x Caramel Chocolate Finger
    1 x Mint Sweets Packet
    6 x Caffeine Sweets (100mg)
    125ml x Natural Energy Drink
    200ml x Minestrone Soup
    800ml x Chocolate Protein Shake
    2 x Big Handfuls of Jelly Sweets

    How Sam's hydration and fueling went...

      • After a strong 5th place finish at the 2022 Dragon’s Back race in North Wales, Sam was looking to secure another top-10 finish when taking on the gruelling 2023 Arc of Attrition in the South West of England
      • Sam worked with the PF&H Sports Science team in the weeks building up to the race to refine his fuel and hydration strategy, with the aim of breaking the 24-hour mark for the 100-mile event


      • Sam drank ~450ml (14oz) of PH 1500 electrolytes with his breakfast on the morning of the Arc to ensure he was going into the race properly hydrated. Science shows that preloading with a strong sodium-based electrolyte drink ~90 minutes before endurance exercise can boost blood plasma volume, which will have helped Sam’s ability to regulate his temperature and reduced the strain on his cardiovascular system during the first half of the race
      • Overall, Sam was able to drink an average of ~313ml (10oz) fluid per hour, with a relative sodium concentration of ~1,139 milligrams of sodium per litre (mg/32oz)
      • We know from Sam’s Sweat Test that he loses 819mg of sodium per litre of sweat (mg/32oz), so his intake of ~1,139m/L was probably more than was required given the temperate conditions. Sam may have overdone his sodium intake slightly, which might well explain the “puffiness” he experienced
      • This said, Sam was happy to share that he experienced absolutely no cramping, which has previously been an issue for him when he’s underdone his sodium intake during events like this
      • Interestingly, when comparing his body weight pre- and post-race, Sam actually gained 3kg (~6.6lbs). This may partially have been due to a prolonged period of maintaining a relative sodium concentration which was too high for his individual losses and so resulted in some excess fluid retention
      • Sam mentioned that he craved Coca Cola from around mile 21. Alternatively known as the ‘Red Ambulance’ in endurance circles, we often observe athletes turning to cola during the latter stages of races as it can provide fluid, carbohydrate and some caffeine all at once
      • Interestingly, he also made sure to include some protein in his fluid intake, which isn’t something we’d say is necessary for performance during a ‘single effort event’ like this whereby he won’t be using it for energy, however it would almost certainly have had a benefit on muscle restoration, via protein synthesis in his post event recovery
      • During extremely long events, especially when they take place throughout the night, it’s extremely common to see athletes exceed the general recommendations of 3-6mg/kg of caffeine. On this occasion, Sam far exceeded this, consuming 20mg/kg
      • Sam has a high tolerance for caffeine and experienced no adverse effects during the race itself, although he reported excessive post race sweating. High caffeine intakes combined with muscle damage have been linked to this occurrence
      • In future races, Sam is going to optimise the timing of his caffeine intake, especially overnight when he’ll be fighting his natural sleep cycle, to exploit the 4-5 hour ‘half-life’, and benefit from the increased perceived energy associated with it


    Quick Carb Calculator Recommendation


    carb 30 mins before


    carb per hour during
      • Carbohydrate loading effectively in the days leading into an endurance event is incredibly important as it helps to ensure maximal stored energy in the liver and muscles come race day
      • To achieve this, Sam ate between 8-12 grams of carbohydrate for each kilogram of his bodyweight for the two days prior to the Arc, and topped it off with a carb-rich bowl of porridge for breakfast on the morning of the event
      • On the 90-minute bus ride to the start line, he ate a PF 30 Chew and drank 500ml (16oz) of energy drink so that he could top up his blood glucose for when the start gun was fired
      • Sam had previously penned out a fueling strategy with the PF&H Sports Science team, which focused on sports energy products, but he felt incredibly strong cravings for a variety of unplanned “real foods” and fluids, especially Coca-Cola, once he was in the thick of racing
      • Despite consuming everything from minestrone soup and jelly sweets, and being force fed rice pudding by his supportive crew (somewhat willingly), Sam was able to achieve an average carb intake of ~87g per hour
      • This is right at the upper limit of the general recommendations for an event of this duration, with our Fuel & Hydration Planner suggesting an intake of ~75g/h. However, it’s extremely close to his pre-planned intake of ~90g/h
      • This is testament to how well he can listen to his body, and how well his self described “granite gut” could tolerate these foods while averaging around seven minutes per kilometre (~11:15/mile) for over 22 hours!
      • Going forward, Sam will be experimenting during training sessions to optimise the format of his carb intake by testing out a variety of different fueling products, rather than changing the already impressive volume of carb he’s able to consume


      • Sam was mostly happy with how he executed his fuel and hydration strategy en route to a 9th place finish at the Arc of Attrition
      • He rated his overall race satisfaction as a 7/10 and he’s focusing on a couple of aspects ahead of his next ‘A-race’
      • Sam took on more sodium than he had in previous races and he reported that he was happy to avoid the cramping issues he experienced in previous ultras. He will look to reduce the relative sodium concentration of his intake, by either reducing his sodium consumption or increasing his fluid intake, to see if this helps avoid the post-race weight gain and “puffiness” he experienced
      • Despite eating a wide range of foods and fueling products, Sam rated his GI comfort as a solid 8 (out of 10). He’s going to look at finding a bit more structure with the fueling products he uses going forwards

    Key info

    Sam Skinner

    Sweat sodium concentration
    Sweat sodium classification
    * determined by a PH Advanced Sweat Test


    Overall Time
    Bodyweight change

    Event information

    Arc of Attrition
    Coverack, England
    27th January, 2023
    Total Distance
    160.9km / 100.0mi

    Race conditions

    Weather Conditions
    No Rain
    Min Temp
    2°C / 36°F
    Max Temp
    10°C / 50°F
    Avg Temp
    4°C / 39°F

    Athlete feedback

    Race Satisfaction
    Hydration rating
    Craving Coke from mile 21 was certainly not the plan!
    Energy levels
    I felt a lot worse overnight in the darkness
    Toilet stops
    I only had two wee stops along the way
    GI comfort
    I've got granite guts!
    No cramping

    Sam's Thoughts

     I think I could have finished closer to 21 hours, but I had a bit of a comfort blanket on and was a little ‘negative’ with my pace overnight

    Sam's full stats

     Carbohydrate (g)Sodium (mg)Fluid (ml)Caffeine (mg)Relative sodium concentration (mg/L)
    Total intake1,9647,7897,0941,5001,098
    Per hour8734331366

    Data Confidence







    There is an adequate level of accuracy in the data collected and the numbers reported. The athlete manages to recall what they ate and drank including most specifics (brands flavours quantities plausible estimations of volumes). However there are estimations made within the data which affect the overall confidence level in the data reported.

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