When is the best time for a beginning runner to start a training plan for a race? It depends on your fitness level and race distance. You should take enough time to safely build up to your time or distance goal but not train too long and risk plateauing or burn-out before your race. If you haven’t been very active, I recommend a minimum 6 weeks if your goal is to finish with some walking needed. For those who wish to run the entire race or have a time goal, a plan of 9 to 12 weeks would be best. The longer the goal race distance, the longer your training plan should be. It takes at least 6 months to safely build up to marathon distance for beginners.