Challenge is achievable by anyone who maintains a certain level of fitness, i.e. regularly in the gym, swimming, walking, etc.

Good fitness level required, i.e. regularly do endurance sports such as swimming and/or runs/walks moderate distances on a regular basis

Excellent fitness levels & stamina required, i.e. often does intensive endurance activities (3-4 times a week / 2 hours plus) and run on a regular basis

Exceptional fitness level required, i.e. undertakes intensive training as well as running.