Western States® 100-Mile Endurance Run

Background:

After Caleb secured the fastest ever debut at Western States® in 2024, with a time that would have won the race in all but two of the previous editions, he thought it was possible to win the race in 2025… and he delivered. To achieve this, he set about optimising every area of his performance, including adapting his fueling strategy to better match the high metabolic demands of running at the faster pace required to take the win. While already well adapted to a high carbohydrate intake after several years of practice, Caleb pushed the boundaries of gut training even further, aiming to exceed what the scientific literature considers feasible. In some training sessions, when running at race intensity, he practised above his target intake by regularly consuming over ~130g per hour to build the tolerance required for race day.

Race Fueling:

From the gun Caleb’s fueling strategy was as aggressive as his pace, which saw him arrive at the first crewed aid station after 3 hours 25 minutes in 5th position, having averaged ~124g/h. Sports Scientist Minty restocked his supplies of PF 90 and PF 30 Caffeine Gels for the short stint to the Robinson Flat aid station less than one hour away. Between each aid station, Caleb’s crew collected his empty bottles and gel wrappers, weighing them to accurately determine how much he had actually consumed. This way, they were able to inform Caleb on how he was executing his strategy on the fly, as well as offer adjustments mid-race.

Having slightly more fuel than he ‘needed’ for the 53-minute run to Robinson Flat (140g carb) meant Caleb could ‘front-load’ his carb intake whilst his stomach was still feeling great, and the not-so-technical terrain enabled ease of consumption. Then, from Robinson Flat to Dusty Corners, he dropped his intake down to ~123g/h, as he prioritised fluid intake after noticing his pee was darker than expected at this point in the race. After leaving Dusty Corner aid station, just over 5 hours into the race, he knew he had a 2 hour 30 minute uncrewed section ahead of him and didn’t want to rely on neutral aid stations for his energy supplies. That was something that tripped him up a little in 2024, so he wisely stocked up on more PF 90 Gels and PF 300 Flow Gel. After this point, his hourly carb intake fell by ~14% as he struggled to consume carbs at the planned rate while suffering from some gastrointestinal distress, likely a result of some accumulated dehydration. Subsequently, Caleb increased his fluid intake, and so was struggling to consume a higher amount of both fluids and carbs.

Caleb recalled that everything had been going so well up until Foresthill (mile 62), but afterwards he began to struggle to take his gels as easily, and his intake dropped below 100g/h for the remainder of the race. This is a relatively normal decline towards the end of ultramarathons, as dehydration, GI stress and systemic fatigue all play a role in reducing appetite and thus carb intake. That’s not to say that Caleb’s carbohydrate intake wasn’t still high, and in fact he never consumed less than ~80g per hour at any point despite his GI discomfort and brutally fast pace! He remained well within the normal recommended amount for a race of this intensity and duration.

In terms of perceptual energy levels, Caleb felt strong until he reached the famous river crossing at Rucky Chucky (mile 78), when he recalled after the race that his mental and physical battle to finish was at its peak, rating his energy levels 2 or 3 out of 10. Diligently continuing to eat and drink, managing his fatigue with brief spells of walking and implementing cooling strategies all helped, but the driving force was the thought of seeing his crew again at Pointed Rocks (94.3 miles). This signified less than one hour of running left, and his energy levels picked up slightly with the thought of seeing his people. He leant on his pacer, his good friend Jacob, to lift morale until the finish line.

Through Caleb’s sweat testing over the years, we know he has a relatively high sweat rate. This enables his body to offload the heat generated by metabolism and heat he absorbs from the environment via solar radiation or the air, and such a high sweat rate is useful for top level athletes aiming to race as fast as they can in hot races like the WSER®. In the lead up to the 2025 edition of Western States®, it was forecast to be one of the hottest editions in a few years, so cooling and hydration were at the top of most athlete’s priority lists. In the early stages, when temperatures were quite modest (~5-15℃ / 41 - 59℉), Caleb’s fluid intake was relatively proactive, averaging just under ~900ml per hour (~3.1oz/h) between the start and Duncan Canyon. However, the temperature swing during this race can be brutal, and by 9am temperatures had hit 28℃ (82℉).

Caleb’s first sign that his hydration strategy wasn’t optimal was when he stopped for a pee shortly before Dusty Corners (38 miles) and realised it was darker in colour than he’d expected at this point. As Caleb visualised the Armstrong colour chart, which can be a valuable tool for predicting hydration status without more refined blood/urine measurements, he determined that his fluid intake was inadequate. So, from this point on, his focus shifted towards maximising his hourly fluid intake. Upon post-race analysis, his fluid intake remained stable between ~1.1 and 1.2L per hour (~37-42 oz/h) from here until the finish. Caleb found this to be just at his limit for drinking, as he trialled taking more in shorter periods, but faced some rejection from his stomach, and was sick trying to do so. After an extensive period of heat acclimation building up to this race to enhance his ability to tolerate the heat, but also to boost his overall fitness, it’s likely Caleb’s sweat rate was higher than he expected it to be. This would largely explain the high fluid intake failing to rehydrate him adequately, so it’d be valuable for him to re-test his sweat rate at similar intensities and temperatures post-acclimation, and plan accordingly for his next race.

Unfortunately, as Caleb ran out of the famous Foresthill aid station, after a rapid pit-stop from his crew, he peed once more and realised the dehydration was worsening, as the colour was much darker despite drinking >1L per hour up until this point. For the next 16 miles, only un-crewed aid stations lay ahead of him, so his plan shifted from “only stop if I need to” to “fill all my bottles at every opportunity”. During this time, the gap between Caleb and second place (and fellow PF&H teammate) Chris Myers, decreased slightly, showing Caleb’s attempt to manage both his pacing but also his hydration, with still another ~22 miles left to run. Caleb’s crew and pacer encouraged him to fully submerge his head during the river crossing at Rucky Chucky, as this was the final opportunity for proper cooling before an exposed, sun-trapped climb up to Green Gate and onwards to Pointed Rocks. The head, face and neck are highly vascularised, meaning they can transfer heat efficiently. Cold water surrounding these areas can rapidly remove heat from the skin and underlying tissue, and likely give a significant psychological boost by cooling the temperature control center in the brain, so stimulate a lower perception of heat, even if there was no direct impact on core temperature.

Similar to his fueling strategy, up until the final crewed aid station at Pointed Rocks, Caleb’s morale, GI comfort, perception of muscle fatigue and motivation, all took a significant hit. But by this point, the most consistent aspect of his performance was his pacing, as he was still one of the fastest on course despite the suffering, and his fluid intake still remained high. Personal preference and aid station frequency determined whether he consumed closer to ~500mg/L or ~1,000mg/L, depending on whether he was drinking pre-mixed PH 1000 (Drink Mix) or plain water from aid stations with Electrolyte Capsules. On average across the entire 14 hours of racing, Caleb consumed an average relative sodium concentration almost exactly the same as his known sweat sodium losses. This comes from professionally dialling in his strategy in training so often that it became second nature. Even when the racing got really difficult and it was hard to focus on much more than putting one foot in front of the other, he was still able to regulate the concentration of his fluids to support optimal rehydration, despite falling gradually behind on his total fluid losses.

Caleb has a decent tolerance for caffeine, but has previously experienced some negative side effects of larger amounts. So in this race, he chose to periodically dose with smaller amounts of the stimulant to reap the associated benefits, treading the line between optimisation and overdosing. A pre-race hit, followed by six further top-ups of PF 30 Caffeine Gel, saw him average slightly over the scientific guidelines for endurance performance enhancement. These guidelines, however, are based on research examining shorter duration events between 3-5 hours, therefore can’t strictly be applied to the demands and durations of ultramarathons. The usual ‘half-life’ of caffeine is 4-5 hours, and therefore in events lasting >5 hours, it’s likely appropriate to top-up blood caffeine levels to continue reaping the ergogenic benefits. This may mean exceeding the guidelines, as Caleb did without issue. You may also notice that Caleb’s total caffeine dose was not equal to six full PF 30 Caffeine Gels which contain 100mg each. That’s because after weighing the gels pre and post-consumption, there was sometimes more than half the gel still in the packet. Due to the stomach issues Caleb was facing (likely due to dehydration), he didn’t want caffeine to exacerbate them, but still wanted to draw upon the performance benefits of the stimulant. He wisely chose to micro-dose along the way, rather than risk over-doing it at any point. Even when he was feeling really rough, he thought taking caffeine was a risk, but was handed a Caffeine Gel to take on the spot at Pointed Rocks, and felt this really turned things around.