Gym workers will spend a gruelling seven hours on spinning bikes as they prepare for an even bigger charity challenge.
Hannah Bladon, centre manager of Aspire Training Centre, and Helen Wright, customer service team leader, will put their muscles to the test to raise money for charity.
The pair, both 27, will do the spin-a-thon in preparation for the London to Surrey 100, which takes place in August.
Ms Bladon, who lives in Borehamwood, said: “It’s a national event and I took part in it last year and said I’d never do it again.
“Helen joined the company and said she would be up for the challenge so I said I would do it with her.”
The pair have so far raised more than £300 but hope to raise a total of £1,500 for the centre.
As part of their training, they cycle to and from work in the rain and take part in spinning sessions at the gym with CEO Brian Carlin every Wednesday.
Mr Carlin took a 12-hour spinathon last month, but the duo hope to go “one better” by having two people in their event.