T100 London

T100 London was Matt's first middle-distance triathlon, so to reduce additional stressors he chose to keep his fueling simple: a PF 30 Gel ten minutes before the swim, then a whole PF 300 Flow Gel in a Flow Bottle between his arms on the bike, and a similar strategy for the run carrying a 120g Flow Flask. That setup seemed to work well for Matt on the bike, where he fuelled at ~121g/h. However, this type of strategy only works when the remaining two of the three levers are pulled in unison. Due to falling behind on his fluid intake during the bike, he experienced some dehydration-related stomach discomfort when starting the run, which caused him to back off the carb intake, resulting in a sharp drop-off to ~37g/h. He did manage to recover his GI comfort slightly towards the second half of the run by targeting cups of water from the on-course aid stations, but still finished the race with plenty of Flow Gel left in his trisuit pocket. Backing off the carbs slightly on the bike would contribute towards a more even distribution of fuel from bike-to-run, plus some ongoing gut training would help him tolerate and use the fuel he's already carrying (rather than bring it home with him).

Matt’s hydration has the biggest room for improvement going into his next race. He rode the whole 80km bike leg and only drank ~600ml of PH 1000 (Tablets), but had 2 x 750ml bottles behind his saddle. With his sweat rate estimated to have been between 0.7-1.2L per hour during the race, drinking ~267ml/h for the bike will likely have seen him well down on fluid before he'd run a step. His own summary nails it: he felt great through the swim and bike and only started to struggle on the run, where the water at the aid stations "resurrected" him. That points to the low fluid on the bike, rather than the fuel, being what upset his stomach early on - as soon as he started drinking properly, his stomcah settled and he found his rhythm. The cause looks practical rather than physiological, which is encouraging. His bottles were mounted behind the seat and were a faff to reach at race pace. So, the most valuable change he can make is simply a setup he'll actually drink from on the move.

The relative sodium concentration of his drinks across the race was a little low given he's a moderately salty sweater. But if he'd managed to drink some of the bottles of PH 1000 he carried round London on his bike, his average intake would likely have been closer to what we'd recommend. So, by tackling the bigger issue at play, the *amount* he drank, he will likely avoid the volume-deficit dehydration which caused his stomach discomfort.