This Overlooked Workout Helps You Build Endurance Without Making Every Run Harder

Most marathon training plans prioritize two or three quality sessions each week: some combination of an interval workout, a tempo effort, and a weekend long run. But between ordinary easy efforts and the aforementioned weekend long run, there’s a valuable space for aerobic development most runners don’t take advantage of to improve performance.This is where the medium-long run comes into play.Coaches explain how this overlooked training tool can help you build more aerobic endurance, add mileage without making every day harder, and arrive at your goal race stronger and more resilient.What Is a Medium-Long Run?Run coach and author Matt Fitzgerald, cofounder of 80/20 Endurance, defines a medium-long run as a run longer than your standard easy run, but shorter than your long run. For example, if you typically run five or six miles on easy days and top out at 14 or 15 miles for your long run, a medium-long run might be eight to 11 miles. However, if your longest run is only 10 miles, your medium-long run should be shorter.In other words, the medium-long run occupies a middle ground. It does not have a universal mileage prescription. The important part is its role in the week: It gives runners another opportunity for aerobic work between their standard easy runs and their longest session, says ultramarathon runner and USA Triathlon-certified coach Nick Farr.When you first introduce these runs into your training, Fitzgerald recommends keeping them easy. A medium-long run describes the session’s duration and purpose, rather than a pace target. It can include race-specific work later in a training block (more on this later), but it begins as a way to spend a little more time building aerobic fitness.What Are the Benefits?Fitzgerald’s central argument in favor of the medium-long run is that runners can gain more from building weekly mileage than from fixating on the distance of one long run.For marathoners and ultrarunners, “your average running mileage for the week as a whole is more predictive of how you'll do in a race than the distance of your longest run,” he says.This does not mean the long run is unimportant. But when it is dramatically longer than every other session in the week, it can take on an outsized recovery cost.Consider a runner who logs four five-mile efforts during the week and then runs 15 to 20 miles on Sunday. That long run is far more stressful than anything else in their plan, Fitzgerald says, and the runner may need much of the next week to bounce back.A medium-long run can distribute some of that endurance work more evenly. Instead of tacking an extra mile onto every run—a move that makes every day a little harder—you lengthen only the medium session and protect the volume of the lighter days before and after, Farr explains. This helps runners increase their weekly training volume while preserving a weekly frequency they can consistently handle.Fitzgerald suggests the groups who benefit the most from this workout structure are marathoners and ultrarunners who want to establish a stronger aerobic foundation.But Farr sees benefits for runners who might be less likely to think this type of session is for them: He views the workout as especially useful for masters runners, newer runners, and runners with packed schedules. For masters runners, a midweek medium-long run can allow for better recovery and reduce injury risk that comes from making the weekend long run as high-mileage as possible. For newer runners, extending one existing session by a mile can add volume before they are ready to add a fifth or sixth running day to their schedule. And busy runners only have to make extra time for more miles on one day, rather than all week.One important caveat: Although it’s not as demanding as a long run, a medium-long run generally replaces one harder workout, Fitzgerald says. It is not an invitation to add a fourth tough session to a week that already includes intervals, tempo work, and a long run.How to Add a Medium-Long Run to Your TrainingFirst, determine the distance of your medium-long run.For someone running six miles on easy days with a 14-mile long run, Fitzgerald suggests beginning with an eight- to 8.5-mile medium-long run. Then, use the first one as a guide: How did you feel after your run? Was it manageable? Did you recover well? Did it leave you with enough energy for the rest of your training week?If you answer yes to these questions, you can work on building from there, Fitzgerald says.As previously mentioned, Fitzgerald’s rule of thumb is no more than three quality sessions per week. If your training schedule currently includes a Tuesday interval workout, Friday tempo, and Sunday long run, a medium-long run would replace either the Tuesday or Friday quality session—keeping the easy days intact. The key is allowing enough recovery between the week’s most demanding sessions, Fitzgerald continues.As far as when to add a medium-long run during your training block, Fitzgerald suggests incorporating it after you’ve built up a base and you’re transitioning into race-specific training. For most runners, that’s about 12 to 16 weeks before race day. Waiting until the final few weeks before a marathon to add in this workout does not leave enough time to build the session safely or reap much benefit from it, he explains.How to Progress Your Medium-Long Run in TrainingStart with an extended easy run, then increase the distance in small increments. For example, moving from nine to 9.5 to 10 miles provides a fresh training stimulus without turning the session into another long run after only a few weeks.Eventually, the run reaches a practical ceiling. If making it longer would put it too close to your weekly long-run distance, Fitzgerald recommends adding controlled intensity instead: a fast finish, short surges, or some marathon-specific work within the run.By adding quality to these longer midweek sessions, “you’re getting in a little extra intensity because you’ve only got so many opportunities to do it,” Fitzgerald says, “but you’re not simply making the medium-long run too hard.”Use two simple guardrails to protect your effort: First, the run should remain substantially shorter than your longest long run. Second, it should leave you moderately fatigued, but not seriously depleted. In other words, it’s fine to feel tired after a long run, but an easy medium-long run should not wreck the next several days of training.The most useful feedback may be how the rest of your running feels that week. Fitzgerald believes runners should feel good most of the time, even at peak training. If your usual ratio of good runs to “meh” runs begins tilting toward “meh,” that is a sign you should probably dial back your training, he says.But when executed well, the medium-long run bridges the gap between easy runs and the long run to build a more complete aerobic week, and helps you reach the starting line healthy enough to race at your fullest potential.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.