week: 9 weeksRunning 5+ days a week: 8 weeksHalf-marathonRunning 2 days a week: 18 weeksRunning 3 days a week: 16 weeksRunning 4 days a week: 14 weeksRunning 5+ days a week: 12 weeksMarathonRunning 2 days a week: Not advisableRunning 3 days a week: 22