If you often find yourself ending an obstacle course race on your hands and knees in a puddle of mud, heaving and sucking wind, it’s safe to say your endurance is pretty weak. Part of being able to rip through a course without curling up into a shuddering ball of shame at the end is coming into the contest with a strong and robust cardiovascular system. And one of the best, and easiest, ways to prepare your body for the constant stress of a race is by running since it mimics the cardio stress involved. 

Running should be a regular part of your Spartan race training, but don’t get stuck mindlessly turning the band on a treadmill or tirelessly trudging through city streets. Head for a local trail instead. Trail running can not only be more fun and challenging than road running, but more stimulating for your mind and better preparation your body for the varied challenges of an obstacle course race, says Jacob Puzey, head coach at Peak Run Performance, and two-time top 10 finisher at the XTERRA Trail Run World Championships. Learn how trail running leaves pavement pounding in the dust and you’ll be a convert.

Trail Running vs. Road Running

It Boosts Your Mood and Calms You Down

“The natural beauty, solitude, and sense of intriguing escape are reasons to try trail running over road running,” Puzey says. “It's hard to get bored on the trails—there’s so much to see and experience.” Soaking in the beauty of green spaces has also been found to help elevate your mood and bring calm. In fast, just five minutes of exercise in the outdoors was found to lift self-esteem and mood, according to a study that appeared in the journal Environmental Science & Technology. (So just imagine the bliss your long run can bring.) 

Related: 5 Essential Trail Workouts for Speed

It Helps Your Overall Health

Exposure to green spaces is a boon for your health, reducing the risk of high blood pressure, stress, and cardiovascular disease, according to a 2018 study, published in Environmental Research in 2018. Staring at the treadmill’s screen or whizzing past split levels and pizzerias, if your neighborhood is less than verdant, doesn’t have the same effect.

It Builds an OCR-Ready Body

Besides improving your mood and keeping you healthy overall, running trails can also strengthen your body in ways that eating up miles on flat and hard terrain like roads can’t. Running on the varied surfaces that a trail offers you—rocks, roots, mud—can help you prevent overuse injuries, says Puzey. “Most of them occur from doing the repetitive motions on the same surface. Trail running involves more side-to-side motion, which helps decrease the risk of overuse injury and increase agility and athleticism.” One caveat: The varied terrain can lead to a higher rate of accidents like ankle sprains, scrapes, and broken bones, so stride mindfully.

Related: 4 Most Common Training Injuries — And How to Prevent Them

It Burns More Calories

The extra motion trail running requires can also be a bonus calorie burner—moving over uneven terrain taxes the body, requiring over 28 percent more energy than traversing flat ground, a study from the University of Michigan found.

Sure, road running is more accessible, since you’re likelier to have easy access to trails rather than roads. But if you’re serious about crushing your next OCR, there’s no better way to get your endurance up than getting yourself to your local trail, or even bounding through a field or grinding on some dirt roads to give yourself a break from treadmill training or road running. “I grew up in a farm town with no mountains or trails,” says Puzey. “The closest thing I could find to trails were dirt irrigation canal roads and grass ball fields—I ran some of my best trail and ultra races while training almost exclusively on dirt roads and doing endless loops around soccer and baseball fields.” Kick ass where you’re planted, as the saying goes.