Marathon Training: How Long Should Your Longest Run Be?

A hot topic among marathon training runners is whether or not one should run more than 20 miles as their longest long run. Oh the 20+ mile dilemma! Here are my opinions on the matter and what I have gathered from helping other runners train for marathons:

Things to consider when determining how long your longest run should be during marathon training:

  • How far your longest run should be is dependent on your goals. If you are training for a specific time goal then I would possibly recommend doing a 20+ mile run at least once before the marathon. If this is your first marathon and you would consider yourself a beginner runner you body is likely to become too stressed with a 20+ mile run and so you should skip it!


  • One should also take into consideration how much time it will take them to run more than 20 miles when marathon training. If you are going to need more than 3 hours then it would be best to save that for the marathon itself as you will be sustaining quite a bit of physical breakdown and you will already be sufficiently overloading your aerobic pathways at that pace as it is and that is the whole goal of your long run anyways!

  • How far your longest run is should also be dependent on the total length of your training plan. If you are going to have to add on more than 10-15% of your total running mileage each week in order to complete a 20+ mile run then save that 20 mile+ run for race day. Your risk of injury (whether major or minor) is too great a chance to take if your body is not ready for it. As you can see with my 32 Week Marathon Training Plan I do schedule a 22-23 mile run because your training plan is so long and you are NOT increasing your long run distance every week but have reduced mileage weeks instead.

  • Running 20 miles is stressful on your body. Depending on the research you look at, running over 20 miles does not give you added benefits to your marathon training. One theory is that if you can run 20 miles then you will be able to add 6 more. Those last 6 miles are going to be a mental and physical struggle either way but the fact that the finish line is there in 6 miles eases the burden.

  • Running more than 20+ miles could be your “peak performance” that your body allows you to do. Therefore, once marathon race day comes around you might have already reached and experienced your physical peak and be coming off of that and therefore not have your grand performance on race day. There is a science to peaking at THE right time in order to have your marathon race day be your ultimate physical performance of your training period versus entering the race with a body that is slightly (or majorly) feeling run down and stressed. You want to be running at your optimal best that day!

  • For those who struggle with mental blocks, it can be helpful to do a run over 20 miles so that they have the confidence that they CAN do it. This should be contingent though on previous mentioned factors, how that runners is feeling (enthused and motivated or ready to have marathon race day here and long training runs over with?), and if there have been any previous injuries along the way.

  • Try to get at least two 20 mile runs in under your belt. Schedule your last 20 miler or 20+ miler to be about 2 weeks before your marathon race date.


  • What do I do personally? I really enjoy the confidence boost that I get with doing one 20+ mile run before the race itself. Therefore I aim to do about 21-22 miles at least 2 weeks before the marathon. To give you some perspective, I usually train for a marathon for about 4 months but my long runs start at about 6-8 miles, I am usually training for a time goal, and I regularly run each week before actually starting a training cycle.

  • Find what works for you. This is the KEY! In the end, it will come down to you, your body and how you are wired! Ask yourself how mentally strong you are. Ask yourself how big of a struggle 20 miles is for you? Do you have more left in you? Ask yourself if you believe you can go another 6 miles. If that's too big of a stretch, in your mind then ask yourself what you feel best about trusting yourself with? 5 miles, 4 miles, 3 miles? Separate how you mentally feel with how you physically feel. Your head may be telling you to stop but your body could actually keep going. Ask yourself how long your training plan is, what your goals are, and how long running 20+ miles will take you. Be honest! And if still in doubt you can always find a running coach. :)

Related Pages to Marathon Training:

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