The agency will deliver a combination of digital marketing, PR and social media engagement, to raise awareness of Jantastic and encourage people to sign up.
The Jantastic New Year challenge gives individuals and teams the structure to achieve personal fitness goals during the winter months by swimming, cycling and running.
The 2014 challenge saw more than 21,000 people log 356,000 runs amounting to in excess of a million miles, prompting the organisers to hire an agency for the first time to increase participation.
Eddie May, co-founder of Threepipe, said: "Jantastic is a brilliant initiative that really helps to encourage and motivate people to get active during those challenging winter months. It was a big success in 2014 and we’re excited about helping to make it even bigger for 2015."