For me it was a mental challenge. I am relatively fit. I swim 60 lengths 3 times a week and have done for over 10 years. I also walk my dogs 2 miles a day every day. But I hated running and I needed a challenge. It took me until week 6 to get the breathing right. But since then I have really enjoyed being out across the fields behind the house. I would recommend the course to anyone who wants a challenge.