St Albans Girls School's running club had more than 20 of their newest recruits involved in the “Couch to 5km course”.
The girls completed the course in times ranging from 27 to 36 minutes. The members met at Verulanium Park to take part in the 5km park run.
The recent heavy rain and flooded lake meant the girls had a tough muddy course over the football pitches.
Year Eight pupil Natasha Holt said: “It was fun running with my friends and we completed the course at our own speed which was very good because it was not a race.”
Many of the girls had never done any running when the course started in the autumn and they have found that their fitness has really improved.
Coach Deborah Steer, who has been working with the Stags cross country team for many years, said: “Running is such an easy sport to get into, all you need are some trainers and the motivation to take the first step.”