Longest Training Run By Race Distance and Why

Recently someone bought one of my training plans specifically the realistic 1/2 marathon plan but life happens and instead she’s working on a 10k. We’ve been going back and forth a bit on adapting one plan for another race (and I’m working on a 10k plan in my mind at least). But it got me thinking… How long should your longest, long run be by race distance? And why? Runners can be a little uptight about the definition of a long run but I tend to be more flexible. Some say anything below 16 km is not long but I beg to differ. If it seems like a long run to you than it is. If you always run 4 k before work them 7 km can seem long and if you’ve only done a handful of 10 k’s a 14 km run seems a big ask. So here it is some guidelines on what you should be building up to for different race distances depending on your experience and expectations. For me a run can seem pretty dang long around 10 k. So if you’re struggling to know what point to get to in your training I hope that helps. If you’ve ever wondered why a particular plan recommends a certain peak week schedule this might give you some insight into that as well. For pictures I included me running each distance, you’ll just have to trust I actually ran that race in that picture.

Long run from two weeks ago

5 K

So my advice here is a little different from the other classic race distances because it’s where a lot of runners start out. I think that if you are planning on running your first 5k you should try a couch to 5k plan because it is the greatest was to start running, really! I’m working on a companion guide to a c25k program now and it’s almost ready!

First timers: In this case I think your longest run in training should be 5k. If you’re a little short 4.5 km is fine but try to get up to the full 5k by race day. Why? Well your first race can be pretty nerve wracking, they often start way too early, you have to sign in, line up and wait. It’s a lot of new experiences all at once early in the morning. Don’t worry if you tell people it’s your first time they will be extra super helpful and runners as a bunch are so so welcoming. It’s a really inclusive culture and though your nervous energy is wasted you’ll probably still have it on the day. For that reason it’s nice to have that crutch that you’ll be fine you’ve run this distance before and you can do it. Plus all that nervous energy is likely to make you go WAY faster and still PR even if you have a few 5k training runs under your belt. Not going out too fast is a big deal in longer races but in the 5k you’ll be fine since it’s relatively short. Your last week might include three runs one 4k, one 5k and one 3k. Once you’ve done that you’re ready to go. PS don’t worry about tapering for this distance.

Pumpkin pacer 5k and PR (yes even in a tutu)

Do overs: If you’re looking to go faster, or run without walk breaks this time a great distance for your longest run in training is 8k. It seems like a lot more than five and it is. I picked 8k because it’s not crazy long and by going 60% more than the distance your ‘I got this’ should be good and strong on race day. By the third km you’ll be saying to yourself. “remember you did 8 k in training, you’ll be fine,” and believe it. Perhaps another 6 k and 5k run in addition to your 8 k long run would be a good peak week for you. Give yourself two rest days before the race.

Michelin Tire Trot 5k Trail Run, free again this year!

10 k

So this is where you’ll start to notice a theme to the first time advice. Save your distance for race day. 10 k’s tend not to get the respect they deserve. I think it’s my favourite distance because it’s a great hour long workout on race day. You’re pushing your body for a solid amount of time and it’s a real accomplishment. But after a 10k you’ll be able to function later in the day and staying in 10k shape is doable year round. I tend to find my self saying that’s it I was just getting started at the end of a 5k where as at the end of a 10k I’m like alright that was great, I’m done.

First timers: Save you’re actually 10 k for the race but just barely. Just in case race day conditions suck, rainy, windy, hilly or early you’ll be sure to still have a PR in your first 10 k. Aim for your longest long run to be 9 or 9.5 km. Perhaps your last week will have a 6.5 k run your 9 k and one 5 k a few days before the race. Aim to also take three days off before your race so you’ll have a set of fresh legs. Three runs a week is fine.

tidal run cov
East Hants Tidal Run 10 k

Do overs: Wile many suggest yo don’t need to taper before a 10 k to rest your body I think it’s a good idea to still respect the concept take three days off before your race and run a couple of slow km the day before. I recommend a longest long run of 13 km. As a percentage it’s not as much extra as recommend for the 5 k. Those extra 3 km at a slower pace will have you on your feet during your longest long run which works out to about 20 – 30 minutes longer than your race and that’s enough to build to. Not all of your weeks should have four runs through all of training but the last two should. So a great peak week, ending 3 days before your race might be a 4 km shake out the day before some speed work of about 7 km, then a day off or two and a 5 km shake out the day before your 13 km long run.

Bluenose 10 k 2017

Half Marathon (21.1 k)

So you’ve decided to line up with the big kids, that’s great! Here is where it’s pretty dang important to do things differently from your first race vs repeat offenders. So listen up!

First timers: I hope you know by now that you’re not very likely to win if this is your first half. I also hope you know training for a half is no small feat. A great and lofty goal for this one is to finish strong and run the whole time. A very small portion of the population is capable of that so take pride in the accomplishment. While there are some well though out half marathon training plans that cover the bare minimum (like mine) the best plan is to be running 5 times a weeks about 5 weeks leading up to race day if not longer. If some jerky marathoner is going to tell you a half is no big deal, no reason to taper, fuel or cross train, they’re not giving you the best advice. Maybe the wouldn’t for a half but you should! Your peak week leading up to the race should end at least a week before race day. A good plan for that week would be a 7 km shakeout the day before 14 km of speed work followed by a 7 km recovery run then a day of cross training before a 8 km shakeout and finally a 20 km long run. Once again we’re saving the whole distance for the day. Chances are your long run will have you on your feet longer than the full race will anyway.

Do overs: Your last heavy training week will look much the same as above but… your longest long run should come in closer to, are you ready for it, 24 km! The idea is you’ll have that extra bit of confidence you need to pull off a PR on race day. You obviously can’t just jump from say 19 km to 24 km so your previous long runs might be the full distance too. Plan on a 20 km and 22 km run the weeks before to prepare yourself! Also prepare some bubble baths!

half cover
Link to what I learned here, kinda sappy really cool.

Marathon (42.2 km)

Now take my advice with a grain of salt here because… I’ve never run a marathon! Right now I never have plans to but as we all know runners tend to get milage creep over time and the average first time marathoner is around 40 so check back with me in 5 years. However… honey did say that if I do a full marathon he’ll take up running with me. Not sure if that’s a promise or a threat yet. But no other distance is as well studied as the marathon so here is some sage, advice.

First timers and Do overs: It is generally accepted that there is no reason do run over 20 miles, about 32 km in preparing for a marathon. The idea is that something happens around the 20 mile mark that kills your body and you only need push past it once, on race day. Running more than that in training is widely regarded as too hard on your body before the race. If it’s your first marathon the best advice is to get two 20 mile runs in before the big day but if you’re looking to get it done better than last time you might have as many as 6 weeks with 20 mile runs! What keeps me from committing to a marathon isn’t the race it’s the training, mostly the time spent training. This is really hard mentally because you’ve never really come all that close to race day milage and mentally that’s a hard thing to do. You’ll be running still for about 3.5 to 4 hours at a time in training and experts agree adding that last 10 k is something you are physically able to do on the big day. This is a big part of why so many people say the marathon distance is mostly mental.


Training plans may differ from this advice and that’s totally okay. The thing is depending on the plan you might not know why, as a lot of plans are little more than a chart with the days of the week and distances covered. I aim for my plans to explain the rational for each workout and week as well as tricks, tips and race day preparations. They’re all over 20 pages and only about 6 of that is the schedule! You can check them all out here. The next one I’m working on is a start running guide that works as a companion for a couch to 5k plan especially helpful for people with health concerns. Stay tuned here for an introductory post when it’s live.

Have you ever done a training plan or race where you felt like your longest long run was too short or too long? If you’ve completed marathons is 20 miles the perfect long run training distance or would you disagree?


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