Traditional thought is that when training for a half or full marathon, your weekly long run should comprise no more than 33% of your weekly mileage.
But the answer is not as easy as a simple formula. Other factors include your average weekly mileage, your age, the race, your experience, etc. There’s even more factors to consider, like, if training for a marathon, I suggest completing your long run every other week. This gives you some rest, where your runs on weeks between is approx 10 – 12 miles.
Other considerations to consider are if you’re younger, less experienced or if you’re training for a 5-8k race where long runs (in excess of 15 miles aren’t necessary).
One of the biggest reasons for this discussion is that runners want to be prepared for their race, but they want to stay injury free. You will always be better when you
In Jack Daniels’ book, Daniels’ Running Formula, he recommends no more than 2 1/2 hours for your marathon long run. However, that’s for someone training for a 3 hour marathon. Depending on your goal time, I’m okay with 3:00 – 3:15, but I don’t think more is necessary. It’s also going to take more than a week to recover from 3+ hour long runs, so don’t complete one of these too close to your race day.
Outside online recently posted an article () where they discussed a safe weekly mileage, using a yardstick called the acute-to-chronic workload ratio (ACWR). The formula is to divide your most recent weekly mileage by the average of your most recent four weeks of mileage. If you keep the number as close as possible to 1, you should be safe. I’ll discuss this article in another post, but my point is that in addition to considering the distance of the weekly long run, you should also be considering the total weekly mileage to ensure it’s safe or smart.
If you’re an Ultra Marathoner, the mileage of your long run may not even be something you consider, instead, the concern or strategy is time on feet.
Lastly, Coach Sage discusses the benefits gained by the body after 90 minutes of your long run. Building aerobic capacity, leg strength, mental & physical endurance or all desired benefits, so there’s no doubt, you need to complete long runs.
My suggestion to determine the best distance for your marathon or half marathon long run is to work with an experienced coach to determine what’s best for you. Don’t simply train to what’s in a “free plan.” Work with someone who knows your specific situation so they can schedule long run distances that make sense for you.