Shaw was sporty as a teenager but by her late teens her body was beginning to show signs of strain and she was in a back brace.
"I have suffered chronic pain for over 20 years. I tried everything - naturopaths, osteopaths, homeopaths, massage therapy, meditation - everything helped me cope with the pain, but I couldn't find someone to say 'Let's fix it.' I wasn't willing to live like that so I kept looking.
"With Sonya, I have gone from strength to strength and have been pain-free for about six months, now."
Horne and Shaw are joined by Shaw's sister Renske van den Brink and friend Maria O'Kane to form Victorious Secret. On April 2, they will line up with 300 other women's teams to SUP, run, mountain bike and navigate their way around a 50km course, and Horne is prepared for some challenges.
"I think the hardest part will be motivating ourselves when we are mentally fatigued, but that is also the bit I am looking forward to the most - supporting each other as a team.
"We may have underestimated the navigation so this weekend Marit's son is setting up an orienteering course for us to practise - we have to find chocolates hidden in the forest."
Despite having little adventure racing experience, Victorious Secret are focused on the event as a celebration for Shaw - and the 54-year-old is bubbling with excitement.
"Contemplating an event like Spirited Women was something that was beyond my wildest expectations. But I look at everything differently, now. I think 'Oh, I could give that a go'.
"In a way I think this has always been me, but living with pain turns you into someone else - I haven't been me since I was a teenager."
Horne has advice for people who identify with Shaw's situation: "Never give up. There is a solution out there for everyone. Don't believe someone who says you can't do something - you just have to find your way."
Spirited Women
What: All-women Adventure Race
When: Saturday, April 2
Where: Rotorua.
For more information: www.spiritedwomen.co.nz