Ever come in from a run, whether it’s your typical Sunday long run or first-ever mile, feeling absolutely zapped? You’re not alone. Chances are, if you’ve laced up your sneakers to log some miles, at some point you’ve found yourself wondering, “Why is running so hard?” The short answer: It’s complicated. And it’s not just you.

In fact, there could be a host of reasons why your run felt super difficult, says Peloton instructor Jeffrey McEachern. From poor fueling to neglecting recovery or needing to adapt to the activity’s high intensity, running taxes your body in unique ways, while also embodying—literally—how you’re feeling during on any given day.

But just because a certain run was challenging or you’re having a hard time getting into the sport doesn’t mean it’s not the right activity for you. Below, learn more from Jeffrey and other experts about why running can feel so difficult, what to do about it, and how to stay motivated even on the toughest days. 

Why Is Running So Hard?

There isn’t a single factor that causes running to feel like a challenge. But experts agree that it can feel difficult because of what it entails at the most basic level: launching yourself forward with a good deal of force. 

We do that to a much lesser extent while walking, but running requires your muscles to move faster and exert more force, explains Nicholas Heebner, PhD, UESCA-certified ultra running coach and associate professor and director of the University of Kentucky Sports Medicine Research Institute. “This increase in speed and force production causes your body to use more energy to propel yourself forward. This is also why running faster, or why switching from walking to running, feels ‘harder,’” he explains.

But that’s just the starting line of why running can feel like a slog. Unlike walking, where one foot is always on the ground, in running, both feet lift off the ground, during what’s known as the “flight phase” of your running gait. To accomplish this, Heebner says, the body demands more from your glutes, calves, and quads to exert higher effort, which can also contribute to that “hard” feeling, he says.

As if that wasn’t tough enough, your cardiovascular system has to join the party by pumping enough oxygenated blood from your heart to your working muscles. This increased blood flow is crucial for delivering vital nutrients and efficiently removing metabolites like lactate so the muscles can continue to function, explains Adam Sebastian Tenforde, MD, director of running medicine at Spaulding National Running Center (part of Mass General Brigham Healthcare) and associate professor of physical medicine and rehabilitation at Harvard Medical School.

“This process of delivering what our muscles need and removing the waste is what makes our heart beat faster and increases our respiration rate,” Heebner adds. This can all contribute to a run feeling hard (including that signature out-of-breath feeling).

Why Running Feels Hard When You’re Just Starting Out

Running can feel particularly hard if you’re just starting your running journey, returning after a break, or bumping up your mileage to prepare for an upcoming race. That’s mainly because it takes time for your body to adapt to the demands of exercise. 

For one, when you start a new activity, like running, your body needs time to learn to recruit the right muscles for the task, and build strength in those areas. “Mechanically, your body hasn’t yet developed optimal muscle coordination, strength, and movement patterns that are very efficient,” Heebner says. “Research has shown us that over time, as runners progress, they become more efficient mechanically.”

Your body becomes accustomed to the exercise, and as a result, you’ll require less energy (or calories) to get the movement done, he says. This efficiency happens at the cellular level as your muscles develop more mitochondria, which are the structures responsible for converting fuel into usable energy.

At the same time, while your muscles are learning how to power your running stride, your cardio system also gets a boost: Your heart and lungs become more efficient at pumping and circulating oxygen-rich blood to fuel your muscles’ hard work. This improved efficiency leads to an increase in your VO2 max, or the maximum level of oxygen your body can use during exercise. In the meantime, though, your heart rate might skyrocket and your breathing rate speeds up while your lungs try to keep up with the demand for air, leaving you short of breath.

As your body undergoes this adaptation process, Tenforde reiterates that it’s natural for runs to feel “hard,” and that it can take time to see improvement. How long will it take? It varies from person to person and can depend on your training as well as a range of other factors like age and fitness experience.

Generally speaking, though, “science tells us that it can take about 6–8 weeks to see significant improvements in aerobic performance that would lead to that effort feeling easier,” Heebner says. “During this time, you can also experience improved efficiency in your running that can make it feel easier. However, this only comes with consistency.”

Why Runs Can Sometimes Feel Hard Even for Regular Runners

Runners know: Some days you’ve got it and other days you just…don’t. Even the most seasoned athletes can struggle through an occasional run, no matter the pace. This can be caused by a score of reasons and factors, say Heebner, Tenforde, and Jeffrey. These factors can include the following.

1. You’re Not Getting Enough Recovery Time

If you don’t allow yourself enough time to recover between workouts, you’re almost certainly not going to perform your best. “A reason why a run or workout may feel particularly hard could be due to poor sleep or recovery,” says Heebner. It’s a good idea to take at least one rest day per week to allow your body to repair any damaged muscle tissue and replenish energy stores. According to a 2021 study published in Nutrients, recovery is a key component in allowing athletes to adapt to new exercise, rebuild muscle, and mentally prepare for the next workout or competition. 

Should recovery fall to the wayside consistently, you may veer into overtraining, which can also contribute to running feeling hard. Overtraining symptoms range from difficulty falling or staying asleep and getting sick more often, to more severe symptoms like high blood pressure or loss of period in menstruating people. Overtraining syndrome can lead to a litany of overuse injuries (such as runner’s knee) and is easiest to address when caught early. If you think you may be overtraining or have overtraining syndrome, be sure to check in with a qualified medical professional like a physical therapist or doctor.

For seasoned runners, taking adequate recovery time might also look like including “down weeks” in which the weekly mileage drops before getting bumped back up, Heebner suggests. This allows the body to adapt, while still feeding your endurance engine.

2. You’re Not Getting Enough Quality Sleep

Scoring enough quality zzz’s can be your secret weapon to staying healthy and injury-free, says Tenforde. According to a study published in a 2021 issue of Current Sports Medicine Report, getting less than the recommended seven hours of nightly sleep, or chronic loss of sleep (not sleeping well three days per week, for at least three months) raises an athlete’s injury risk 1.7 times. What’s more, research in a 2023 issue of Sleep Medicine Clinics stated that athletes who had disrupted sleep reported increased resting heart rate, higher lactate levels, and a decreased VO2 max while performing various test exercises.

 Sleep can also aid in your recovery and ability to bounce back—and not just from your run. “Sleep is when our bodies have a chance to repair and recover from the day. Not just the physical part of the day, but the psychological load of the day as well,” says Heebner. “If you’re just starting out, you might find you’re more tired at the end of the day once you integrate more consistent physical activity into your schedule. Don’t be alarmed—this is normal and it’s just a sign that your body is ready to get into recovery mode.”

3. You’re Not Fueling Properly 

Running is a high-intensity exercise and therefore requires appropriate fueling to help your body crush miles—and recover once the workout is done. While it’s possible to achieve the proper nutrition from a range of eating styles—from vegan to Mediterranean—it’s crucial to eat whole foods. “Keeping a healthy diet throughout the day will help keep your energy levels up and you fueled for your runs,” Heebner says. 

Maintaining a healthy diet can also help you recover more effectively, adds Tenforde. “Part of training adaptations is rebuilding tissue damage sustained due to exercise,” Tenforde says. “Adequate protein to rebuild lean tissue and carbohydrates to restore local tissue stores of glycogen are needed for tissue recovery and performance.” To help rebuild these muscle tissues, Tenforde recommends having a high-protein snack within 15–30 minutes after your run to speed up recovery.

Don’t skimp on hydrating either, Tenforde emphasizes. To ensure you’re staying hydrated, keep an eye on the color of your urine, he suggests. Ideally, it’s neither clear (which would indicate you're overhydrated) nor dark yellow (which would indicate you’re dehydrated.)

If you’re interested in optimizing your nutrition for your runs—or life in general—it’s best to consult with a registered dietitian for personalized guidance.

4. You’re Struggling with Your Mental Health 

Everyone goes through tough seasons. “If you’re going through something in life, a time of transition, changing jobs, your kids starting school or [something else] in your private life, make sure to account for that energy being taken from you,” Jeffrey says. Various life chapters and circumstances can stress the body and mind, leaving less energy to devote to your runs, he concludes. According to research published in a 2023 issue of Sports Health journal, mental health disorders can not only make athletes more prone to injury, but they can also impact how quickly they recover—and perform once they’re physically healed.

If you’re struggling with your mental health, be sure to find support in a licensed professional like a counselor or therapist.

3 Ways to Make Running Feel Easier

Just because running feels hard at the moment doesn’t mean it always will. While proper fueling, training, and recovery are important, there’s more you can do to build strength and endurance to help make your runs feel easier.

1. Prioritize Consistency 

“The phrase ‘an object in motion stays in motion,’ isn’t just from your physics class,” says Heebner. “It's also true about exercise and running. Running will get easier but only if you stay consistent with it. As you gain fitness in your running the paces that you run at will feel easier.”

2. Slow Down 

It might sound counterintuitive, but to go faster, it’s beneficial to prioritize slow, easy runs. How can you tell that you’re hitting the right pace? Jeffrey likes to implement the “sing test,” which is basically the “talk test,” but with flair. “If I can sing along or hum along to my favorite song, that’s a good pace for me,” he says.

If you have trouble pacing yourself, try a guided running workout like those offered on the Peloton App; an instructor will coach you through speeds, pace targets, or rate of perceived exertion (RPE) to help you manage your effort.

3. Find (or Build!) Your Community 

It doesn’t matter how fit you are; some days it’s impossible to get motivated to run. That’s where a running community can come in. “One of the best ways to not only make a run feel easier but also help with consistency, or at least more fun, is to run with a local run club or with friends. Running with other people that share a common interest can lower your perceived effort level. This is also great to help keep us accountable for our runs,” says Heebner.

 On the Peloton App, consider joining or starting a Team to connect with friends, family, and fellow Peloton Members across the globe, cheering each other on as you reach your goals. 

How to Return to Running After a Break

Whether you’re returning to running after having a baby, recovering from injury or rebounding from burnout, getting back into it can feel intense. However, taking a slow and conservative approach to get back into the swing of it will help ensure that you stay healthy while enjoying the process (yes, really).

 First, if you’re overcoming an injury, Tenforde points out that you need a diagnosis from a licensed medical professional to devise a strategy to get back into running. Conditions like tendonitis, for example, have very different recommendations to more serious bone injuries, like stress fractures.

Once you have a plan in place, you may notice your physical therapist, coach or other guidance has suggested trying a walk-run method. This is when bouts of walking are alternated with short (and often, slow) bouts of running. Over time, as you safely rebuild muscular strength and endurance, the walking intervals will decrease in frequency and duration, while the runs lengthen, explains Tenforde.

 If you aren’t dealing with an injury or other physical condition, Heebner advises easing back into running, allowing your body to serve as a compass on how much (and how fast) it can safely tolerate. After about two to four weeks of no training, your aerobic performance begins to deteriorate, he says. What’s crucial is to allow your body time to reacclimate to the activity, and try not to get discouraged if you’re not immediately back to your former mileage or paces.

Guided training like Peloton’s You Can Run programs, available on the Peloton App and equipment, can provide a framework for your training, and help you progress at a slow and steady pace.

No matter the reason why you’ve been away from running, it can feel hard when you’re getting back into it. But, by prioritizing patience, recovery and proper nutrition while maintaining a healthy mindset that gives you grace (and encouragement) on the most difficult of days, you’ll be able to put the past (and more miles) behind you.