Beginning in 2010, Parnell set out to complete ten ambitious athletic quests while raising money for children through sport and play programs. The challenges ranged from 250 marathons in a single year to endurance events in netball, lacrosse, soccer and hockey, a 100-kilometre run on Rarotonga, the Kilimanjaro Marathon followed by a rapid ascent of the mountain, and multi-stage running and cycling events.
The projects required sustained training, logistics and fundraising, but in early 2015 a large blood clot on Parnell's brain abruptly changed the direction of his life. Hospitalization and an extended period of restricted activity forced an endurance athlete accustomed to constant motion to confront recovery and uncertainty.
Running to the Edge combines sports memoir and philanthropic adventure with a quieter account of what happens when physical limits can no longer be ignored.