JAMIE Milne is on his own working his way through a national park and doing it tough on the fourth day of a two-week attempt to run around Tasmania.

The Warana gym owner who specialises in training ultra-athletes is on schedule running 80 kms a day in a bid to cover the 922km distance within the restricted time frame.

But his first support crew had to head home this morning which has left him without food or water and about 10km from Tullah Lodge on the island's west coast.

"I've seen five people in three days,'' he laughed.

"There's just trees and road kill, though the few people I have met have been absolutely wonderful.

"Today will be good once I get some fluid into me. I'm 100% on schedule.

"I'm looking forward to a decent feed and a couple of ciders."

Day one of the ultra marathon saw Jamie run from Hobart to Hamilton and then onto Bronte Park the next before a run to Queenstown with its stunning scenery.

On day three a "stupid" video he shot and posted online quickly attracted 1000 likes.

Top cover the distance he needs to on the Tasmania run, which will raise funds for Hobart's Ronald McDonald House, Jamie gets up at 4am to start running for 12 hours at 5am.

Last year he ran the 650km from the border with England to the top of Scotland and he's also run the length of New Zealand's north and south islands twice.

Milne is also the author of the 2010 publication "12 Weeks to an Ultra Marathon".