Cyclist starting running

Mr Twinklemel has decided to take up running, got properly fitted for running shoes etc and all seemed to be going well.

However, last sunday he went out for an hour long cycle (fairly short for him), came home, changed into running gear and went out for his walk 1 min, run 1 min circuit, which takes around 20 mins for him to get round.

He came back in pain, saying that the muscles between his ankle and calf, up the back of his leg, had siezed up, getting tighter and tighter and they were visibly swollen when he returned home. They were sore for a couple of days after.

Any ideas what he's done wrong?

Too much too soon? or maybe he was going too fast?
You use slightly different muscles running so maybe his body didn't like it

Otherwise I suggest he sees a physio to check out biomechanical problems

As I understand it from triathlon literature (I'm a runner who occasionally tinkers with doing a tri) you have to be VERY careful on the bike/run transition because the bike tends to shorten your hamstrings, where running tends to stretch them. So if you jump off the bike and go straight into a run, particularly if you're not used to doing so, the result tends to be a pretty instantaneous hamstring pull, especially if you set off on the run too fast.

The recommendation, if you're going to make this transition (bike-run) regularly, is over the last mile of your bike ride to stand up in the saddle and gently ease out your hamstrings on each rotation of the peddle. Then stretch when you're off the bike, and start running at a seriously slow pace for 50 yards untile the hamstrings have started to fully flex out.

Is it cramp ?

I used to run to a spin class and run back again and my calf muscles would try to cramp about a minute or two into the run home. It went away when I kept ignoring it though - but osd's tip seems sensible.

similar to OSD, but i can never be bothered to stretch or stand up, so instead i just start off taking very small steps for the first k or so off the bike. also in the last k of cycling i go into a very low gear and spin the old legs, wich seems to help.

I took Mr CO's advice when having a similiar problem and it worked very well.