Missed Miles in Marathon Training? Here’s What You Don’t Want to Do When Catching Up.

Missed marathon-training miles rarely come from one big disruption. More often, a shortened easy run here and a skipped one there leave a few blank spaces in an otherwise steady week.By Friday, those missed miles can leave a small gap in your weekly total. And when you’re already planning to spend a few hours on the road during your Sunday long run, tacking on a few extra miles can seem like no big deal—a simple way to keep the week’s mileage on track. But experts say this seemingly harmless adjustment is a huge mistake.Missing a few runs won’t ruin a marathon build. But trying to force those miles back into one already demanding effort can turn a minor disruption into a bigger setback—raising your recovery demands, muddying your fitness progress, and compromising the training still ahead.Ahead, coaches break down how to rework a disrupted training week without overloading your long run and how your long runs can help you gauge race-day readiness.The No. 1 Mistake When Trying to Make Up for Missed RunsA planned long run is already one of the week’s biggest physical stressors. Add a few unplanned miles on top, and you increase fatigue and recovery demands at a point when you have not established the supporting volume to absorb them. “That’s the recipe for disaster,” Janelle Brade, a UESCA-certified coach, previously told Runner’s World.General guidelines suggest your long run should account for no more than 25 to 30 percent of weekly mileage, Kai Ng, a New York City–based RRCA- and USATF-certified run coach, previously told Runner’s World. For example, that means if a 16-mile long run in a 48-mile week becomes anything longer, you’re pushing well over the top of that line and elevating your risk of injury.Why Protecting the Long Run Is So ImportantGradually increasing the distance of your long run develops endurance and durability while giving you a place to practice fueling, pacing, and staying composed on tired legs.The goal of a long run isn’t to jam the rest of your weekly miles into one huge effort; it’s to teach your body to handle longer distances and more time on feet—and to recover well enough to keep your training going, Roberto Mandje, a former Olympian and coach, previously told Runner’s World.It’s for this reason that Flagstaff-based run coach Kim Conley, a former Olympian in the 5,000 meters, also told Runner’s World that she caps beginner long runs at three hours rather than forcing an exhausting mileage target.A well-designed long run can offer a useful read on marathon readiness. For experienced runners, controlled marathon-pace work within a long run can show how goal pace feels under fatigue and help determine whether that target is sustainable, Conley says.The longer effort also gives runners a chance to test race-day fueling strategies. But tacking on extra mileage can undermine this test and create a workout your body isn’t ready to take on, Brade says.How to Rebuild Mileage SafelyIf you’ve missed mileage on your marathon training plan, start by spreading small additions across the lower-intensity efforts on your schedule. Brade recommends adding about five to 10 minutes to your midweek easy runs—making a 40-minute easy run 45 or 50 minutes, for example—which allows you to gradually restore volume without creating another run day or making the long-run mistake.If you are lagging behind in weekly mileage or have not built yourself up to the planned long-run distance, Brade recommends splitting that effort into two runs: an easier, longer effort one day, then a shorter session with goal marathon pace work the next.If you’re managing a recurring niggle or struggling to recover from your current training load, adding more running may not serve you well. In these cases, Brade suggests adding a 10- to 20-minute bike ride after a 30- to 40-minute easy run to build aerobic time with less pounding.Mandje notes that a couple of lower-mileage or broken weeks do not ruin a marathon build, but you cannot cram missed adaptations into one weekend. If your long run winds up exposing a lack of durability for a planned pace or distance, adjusting your goal time is smarter than forcing a workout your body is not ready to handle.Matt Rudisill is an Associate Service Editor who has been with Runner's World since 2025. A Nittany Lion through-and-through, Matt graduated from Penn State in 2022 with a degree in journalism and worked in communications for the university's athletic department for three years as the main contact and photographer for its nationally-ranked cross country and track & field teams. Matt was also heavily involved in communications efforts for Penn State football, men's basketball, and women's gymnastics. In his role with Runner's World, Matt has interviewed Olympians, world champions, and countless experts in the field to create service content that helps runners of all ages and experience levels train smarter and race faster. When he’s not out jogging, Matt can be found tweeting bad takes about the Phillies or watching movies.