plus some dehydration
MaxHawk wrote:
If the best marathoners ran for 6 hours straight their legs would probably look like that. The reason TDF bikers legs look like this is a 'perfect storm' of three factors
1. Very lean, shows veins. Runners also have this going for them.
2. Very strong cardiovascular system, they pump A LOT more blood around especially into their legs. Again runners have this going for them.
3. Long duration of activity, this is the kicker, since they are in the saddle for so long day after day the blood spends a lot of time in their legs meaning the veins really pop. This is where runners vary- I haven't seen pictures of ultra runners legs at the end but I could imagine they look similar.