I'm discovering the running and I like it.

I currently have race two 10km events (1 hour) and one 22km (2h 15') autonomy in a park.

During the 20km race I had very little bad knee, perhaps due to the fact that the path had many ascents and descents.

Currently I can train for 5/7km no more than once a week, but I would try to run a marathon.

More than this run I go to swim twice a month (about 1h+30') and 2/3 time cycling (about 4/5h each time).

I do not care the end time (the limit is 5 hours and I should be able to do it), but I want to finish it.

What risks could meet without adequate preparation?

2 Answers 2


5km or 7km mileage once a week is nowhere close to proper preparation for a marathon. You greatly increase risk of injury by running a marathon unprepared.

Go see a doctor about your knee pain from the 20km race and forget about a marathon anytime soon. Many marathon plans have a long run of over 20km once a week for several months (and often with a run or two of close to 30km). You total mileage goal of 5 to 7km once a week is completely inadequate.

If your knee is the problem, wait and let it heal. If time constraints are holding back your mileage then focus on training for much shorter races.

42.195 kilometres is a long distance. Follow a proper marathon plan and take it seriously:



If you were to decide to attempt a marathon given the training level you've described, there's an interesting academic article that may be helpful in estimating your likelihood of finishing without injury. The paper is by Yeung, Yeung, and Wong, "Marathon finishers and non-finishers characteristics: A preamble to success," Journal of Sports Medicine and Physical Fitness, 41(Jun 2001):170-176.

The researchers surveyed 113 registered runners at a Hong Kong marathon, of whom 55 finished and 58 were unable to finish. The predictive variables that had overwhelming explanatory power (p < 0.005) as to whether or not a runner would finish were:

1) weekly training mileage -- the training distance, per week, of the average finisher was 52km (32mi) whereas for the average non-finisher, it was 9km (5mi);

2) length of the longest run accomplished during training -- 28km (17mi) for the average finisher vs. 5.4km (3.4mi) for the average DNF (did not finish); and

3) the runner's personal opinion of how much training was needed to do a marathon -- that is, how difficult did the runner think a marathon would be? The average finisher assessed 72km (44mi) per week as optimal marathon training whereas the average non-finisher thought that only 29km (18mi) per week would be sufficient.

Given your question it seems that all three predictive variables (in their current state) are pointing towards a prediction of non-finishing.

Your question also asked about what the risks were if you did decide to attempt the marathon at this point. The same paper includes a breakdown of the non-finishers, that is, why did the non-finishers not finish? Of the non-finishers, 43% dropped out of the race from exhaustion, 35% stopped at the 10km mark due to missing the time cut, 19% were injured, 2% were advised at a medical tent to stop, and 2% reported "other."

  • Very interesting report. I add that I go to swim and to bike over the running, and I think I will try a run of 30km as soon as the work give me the time
    – Ale
    Jun 22, 2016 at 16:24
  • 3
    Other studies (for example, Satterthwaite et al, 1999) have shown that cross-training (bicycling, swimming) is indeed correlated with a lower incidence of running injury in marathons. However, the evidence for this is weaker both in terms of strength of effect and direction of causality. So, while it is a positive sign that you also bike and swim sometimes, I would recommend caution against over-estimating the importance of this detail, relative to your overall situation.
    – intj440
    Jun 22, 2016 at 16:47

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