The thought of never being physically active again was gut wrenching.

The Glen Waverley resident and teacher at Melbourne Grammar was playing football in 1994 when he dislocated and broke his ankle. He suffered 21 operations, including one in which his ankle was fused.

"I was someone who had been very active from a very early age and I played footy for about 21 seasons," the 37-year-old said.

"To be told I couldn't do that, I was a bit lost, to be honest. I had a really frustrating 18 months of my life where I was hobbling around in a moon boot."

But this April, Mr Williams started jogging again. He decided to take the plunge after being able to walk without pain.

After a successful one-kilometre run, he and three other teachers decided to regularly run together and keep each other motivated.

"We just continued to build on that and went up by a couple of kilometres each week. Two weeks ago we ran 95 kilometres for the week." They now have the Melbourne Marathon in their sights.

The gruelling event, held on October 9, is 42kilometres long and the group is hoping to run it in less than four hours.

The quartet will be taking part in the race to raise money for the Monash Children's Hospital, which has treated a number of students from their school.

Mr Williams keenly remembers his own

frustration and said the group wanted to help sick children get over their illnesses as soon as possible so they wouldn't have to experience that.

The group has been training at least four times a week and some mornings meet at 4am to get in a three-hour run

Although it is a daunting task, Mr Williams says the group will complete the marathon.

"I don't know what state we'll be in when we get to the finish line, but we'll get there."