For most runners, the question of how long their long run should be isn’t about trying to find the upper limit. The goal is more about trying to figure out the bare minimum they can do while still being able to hit their goal distance on race day.
Rarely does the average runner have more than three hours to spend slogging through long miles most weekend days, thanks to other non-running obligations. Without all of the other factors in place around training — getting enough sleep, eating enough, spending time on mobility, taking time for recovery — that the pros have access to, recovering from long runs can be nearly impossible.
Even in the most elite runners, long runs and races temporarily depress the immune system and other normal bodily functions, making high mileage weeks tricky to navigate.
The general rule of thumb for runners is your long run should only make up 20–30% of your weekly mileage. So, for example, if your long run is 30 miles, you shouldn’t be running more than 100 miles per week, which isn’t actually a very helpful gauge since very few people run that much. Because of this, most marathon plans top out at around 16 miles, since that can mean a 50-mile total training week — much more doable for the average runner, though still a high volume of running.
This rule doesn’t offer a lot of insight into exactly how long a long run should be, but you can use it in two ways by revisiting some of those high school math class word problems you used to hate:
This rule can be a good starting point for planning the rest of your week around your long run to avoid overtraining. If you’re running 12 miles on Saturdays, your mileage shouldn’t go over 40 miles total for the remainder of the week, since 30% of 40 miles is 12 miles.
Another option is to use this formula to reverse engineer your current week to find a good starting point for your long run. If you’re currently running 5 miles six times per week for a total of 30 miles, you can do the math to see your long run should be between 6 miles (20% of weekly volume) and 10 miles (30% of weekly volume).
MILEAGE ISN’T THE ONLY FACTOR
Remember your long run will only benefit you if you do it correctly. That means slowly building up to your long run, rather than jumping from 4 to 10 miles in a single session. It also means fueling your run adequately: If you’re out for more than an hour, you need to bring some form of fuel and plan for hydration. This means carrying a bottle, wearing a pack or donning a belt with bottles attached. Start making this a practice as soon as your runs tip into the 60+ minute category to train your body to better absorb fuel. Don’t wait until you ‘feel fast enough to need it.’ Don’t forget, fueling is about time spent running, not miles. When you get started, your 7-mile run may take 90-minutes and require you to fuel during it. In a year, that same 7 miles might be over in 50 minutes, meaning you can leave the bottle at home.
To add more miles to your long run when you’re relatively new to running, consider walking before and after your longest run to add a couple of miles without adding much stress on your body. This is a great way to practice being out for long periods of time on your feet and continuing to fuel adequately. This is important if you’re prepping for a long race like a marathon but want to lower the overall impact of training stress on your body.
THE BOTTOM LINE
Long runs have a certain glamour and allure to them: They feel epic, tough and can make you feel like a ‘real runner.’ Just make sure you’re approaching them with caution and easing in — there’s no definitive right or wrong number of miles that constitutes a long run.