You just spent months building the fitness necessary to complete 26.2 miles. It’s tempting to want to keep the momentum going post-race—until you head out for your first run and start asking yourself, to quote Des Linden nine days after setting the Master’s record in the Chicago Marathon, “Errrm, where did all that fitness go?”

After a big running event, you don’t want to just hop back on the hamster wheel. Respecting the post-marathon recovery period is crucial to making long-term gains, and most runners will benefit from at least one to two full weeks off from running. That may sound interminably long (it’s not, and even more of a break can be beneficial, too), but here’s why your body needs that time-out in order to come back stronger.

Don’t Rush the Comeback

Unfortunately, just like the only true cure for a hangover is time, you can’t fast-forward through the post-marathon recovery period.

“People think they’re just recovering from that one day, but that’s not it,” says Toni Kengor, co-founder and full-time running coach for Relentless Runners. “You’re recovering from the last four months or so that lead up to the marathon. I think people underestimate the physical and mental fatigue that occurs in that process, and that your body and brain need some time to just relax.”

Sore muscles are one of the major ways your body waves a white flag post-race, but being able to comfortably walk downstairs or sit on the toilet without holding onto the sink doesn’t give you the immediate go-ahead to get back to training. You may not be able to feel the recovery process after a certain point, says Laura Norris, a certified running coach, strength and conditioning specialist, and exercise scientist based in Colorado—but you better believe it’s still happening.

“Research shows that a marathon triggers a systemic inflammatory response,” explains Norris. “In the hours and days after completing a marathon, various inflammatory biomarkers such as creatine kinase (an indicator of muscle breakdown), c-reactive protein (an acute inflammatory response), troponin (which indicates acute damage to cardiac muscles such as heart), and lactate dehydrogenase (another indicator of tissue damage) are all elevated.”

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Translation: Your whole body—including your musculoskeletal system, nervous system, respiratory system, cardiovascular system, and endocrine system—are all impacted by the highly stressful bout of prolonged exercise, says Norris. “You can’t rely on a metric from a singular system (say, less soreness in your muscles) to ensure that all systems are fully recovered,” she adds. “More than likely, soreness will subside within a few days, but that does not mean that other systems are ready for exercise again.”

In fact, it can take up to four weeks for your body to fully recover physiologically from “massive aerobic exercise,” older research published in Free Radical Biology and Medicine determined. And that doesn’t even address the mental aspect of training and racing. “Your life has been dictated by this event for four months or so, and that’s on top of life stressors as well,” says Kengor. “That’s so mentally demanding, it’s important to give your brain time to relax post-race.”

Do You Lose Fitness by Taking Time Off?

Sorry to say it, but, yes, you’re probably going to lose a little fitness during the post-marathon recovery period. A loss of cardiovascular fitness and endurance starts to happen after as little as 12 days of no exercise, a 2020 literature review published in Frontiers in Physiology found.

But your body needs that break, because runners aren’t meant to maintain peak fitness all the time. “Most marathon training plans push you into functional overreaching before the taper,” explains Norris. “If you jump back into hard training too soon after the race, you could risk reaching the point of non-functional overreaching or overtraining.” And that can lead to fatigue, declining performance, and a host of adverse health outcomes.

Fitness progress isn’t a linear journey; you’ll have periods where you’re increasing volume and intensity, followed by periods of de-loading or down time, says Kengor. Those rest or recovery periods—which allow your body to make the necessary adaptations to the stress you just put it under—are what allow you to continue pushing your limits.

“It’s similar to how we slow down to speed up,” Kengor explains. “A lot of people don’t trust that until they try it for the first time, and then they see the positive effects and wonder why they weren’t always doing it.”

You worked so hard to get to peak fitness, and the fear of losing it is understandable. But you’ll return to those high levels of fitness more quickly post-race than it took for you to reach them pre-race, older research published in PNAS determined.

“Most runners return to their fitness baseline in a week after a marathon—even if they take that whole week off of running, research has shown,” Norris says. “Even if you were to barely run for a few weeks post-marathon, fitness loss would not be significant. It takes a full six weeks for significant changes in musculoskeletal adaptation. Taking one to two weeks off post-marathon will not induce significant losses of fitness.”

How Long Until You’re Fully Recovered?

Every runner responds to a big physical undertaking differently. Most runners should plan on a minimum of 7 to 10 days off of running post-race, says Kengor. Yes, you might feel antsy, but before you jump the gun, remember that this is generally how long the pros take—Linden just happens to have a trail adventure in Japan on deck. Case in point: Last year, Aliphine Tuliamuk posted about taking a two-week break after the New York City Marathon, and Lauren Thweatt posted about taking three full weeks off after the Chicago Marathon.

But a “break from running” doesn’t mean no exercise at all! “Exercise is a part of post-marathon recovery,” says Norris. “In fact, once you get past the initial rest phase immediately after a marathon, the blood flow from exercise will help you feel better sooner. It’s a fine balance of not rushing back, but also moving soon enough to help your body feel good.”

RELATED: A Deep Dive into the Science of Marathon Recovery

Low-intensity activities like short walks, yoga, Pilates, and even light swims or gentle cycling lasting less than 45 minutes can be great for your body during that first week or 10 days post-race.

From a running perspective, the key is easing back into things. After two weeks post-marathon, Norris recommends re-introducing easy 30- to 45-minute runs. At three or four weeks, you should only be at around 50 to 60 percent of your pre-race average training volume. “I personally don’t even introduce any workouts until after at least four weeks,” says Kengor. Upping your intensity too soon also increases your risk of injury, adds Norris, but “by then, the musculoskeletal system should be able to tolerate harder effort and increased mileage. This may seem conservative, but the athletes whom I’ve implemented this with have long-term development and a low rate of post-race injuries.”

And if you feel terrible—à la Des Linden—on your first run back, that’s not only due to significant loss of fitness. “Instead, the necessary time off may result in some dampened neuromuscular activity and slight reductions in blood volume, which may make a couple runs feel temporarily harder, but both will rebound within a few sessions,” says Norris. “You may also feel bad because you are still recovering on a cellular level, or because your mind is still rebounding from the mental strain of training and racing.”

The guidance above is generalized. If you go out for a run and it feels forced, it’s OK to stop and/or extend your break, says Kengor. “I think people need to learn to pay attention to how they’re feeling mentally on those initial runs back because I think that’s an indicator of where you are in the recovery process. When you’re mostly recovered, your legs may not feel the freshest they’ve ever been, but it shouldn’t feel like a slog.” To reach that point, you may need more time than the runners you follow on social media, and that’s OK! Running will be there when you’re ready.