Limiting factor in endurance events.

In my Ironman, I got debilitating calf cramps at mile 24. In the 3 marathons I’ve done, it’s always come down to my calves slowing me down towards the end of the race.

I’ve usually worn calf sleeves thinking it helped. But today I went without them and it actually went a little better than usual.

I’m staying up on electrolytes and carbs during races, lungs felt fine, everything else felt fine. But calves shut me down.

Any advice? I’m wearing Mizuno Wave Runner shoes, which I’ve always liked.