Half marathon charity runner Lachie Spark is running from Hobart to Cairns for mental health.

Each day, Lachie runs 21 kilometres, the equivalent of a half-marathon every day.

He kicked off his trip in February and has just cracked 100 days on the road.

You can donate HERE

Lachie told Ben Fordham he’s hoping to reach Cairns for his birthday on September 17.

“Every part of me has had a real struggle. At the moment my toes are in a world of pain – I’ve been running through floodwater and all sorts of horrific conditions.”

Press PLAY below to hear the full interview