People panic about being slower in the swim. Say you're aiming for two minutes per hundred metres and you come out of the water at 2:08 instead, that's about five minutes slower than planned.
But the swim's only 3.8km. The bike is 180km, the run is 42.2km. Put those together and the bike and run add up to 222km, fifty eight times more distance than the swim to find that five minutes back in.
The maths on the bike
Say you're riding at 30km/h. To claw back five minutes over the whole 180km, you'd only need to ride 0.4km/h faster. That's not even a gear change, maybe a few more seconds in aero per kilometre.
Or on the run
If you're running five minutes a kilometre, making up that same five minutes over a full marathon only needs seven seconds a kilometre quicker. One deep breath and a bit of a dig, each km.
Split it across both and it's barely noticeable at all, about 0.2km/h on the bike and three seconds a kilometre on the run.
Same five minutes lost either way. But you've got 222km to find it in, not 3.8. That's why I don't panic when my race swim comes out slower than training. Losing time on the shortest leg doesn't decide the race, there's far more of it left to make that time back in than there was to lose it.
