On a recent trip to Sun Valley, ID (courtesy of Smith Optics [1] and the Sun Valley tourism board [2]), I was greeted with dappled skies, perfect weather, and mountainous terrain. Nestled among famous rock-climbing routes and high-altitude lakes, the ski town was the perfect setting for a trail run and hike. The problem? While I love to run on sidewalks and asphalt and through the park — you name it — mountain trail running is a whole other skill that I've yet to master. I envisioned having to get carried off the mountain after an unfortunate encounter with a jagged rock or a slippery, sandy downhill trail.

Luckily, my group was led by two pros who helped us feel at ease with even the thought of running on rocky, uneven trails: Golden Harper, founder of Altra Running [3] shoes, and Zac Marion, an Altra Running team member and winner of the 2014 Bryce 100 [4] (as in, 100 miles of grueling, uphill terrain). They briefed us on a few important tips anyone who's ever wanted to take her normal hike to the next level needs to know. Read their advice below on how to stay safe while trail running.

When Going Uphill

• Bounce: When things get steep, you may want stop, but walking actually requires more effort for your body, Zac explains. The solution: instead of dragging your body up the mountain, take quick, little steps, and bound uphill. "Counter to what you actually might really think — 'I'm running: it's actually going to be harder' — it actually is easier. It's more efficient on the body," he says.
• Run proud: Fight gravity and fatigue, and keep your chin up. "Puff that chest out," Golden says. One trick he says keeps him going when he's low on energy — pretend the moon is up just over the horizon, and do a few quick pulses up with your body toward it. "It'll bring your chest and hips forward and put you in a really good position," he says.
• Step on rocks, not over them: Behind those rocks and tree roots could be something else that could hurt you. "If you leap over it, you don't know what's on the other side if you can't see it, and you could roll an ankle," warns Zac. Train yourself to land on obstacles to keep safe.
• Minimize arm movement: "Ninety percent of runners use their arms too much," Golden says. Instead of wasting energy, keep your elbows behind you as you pump your arms, unless you're sprinting up the hill.

When Going Downhill

• Look ahead of you: Looking down at where your feet are right now is a recipe for ankle-rolling disaster when running on trails. Instead, look three to five feet in front of you, says Zac. "You want to see what's coming up. If you look and you say, 'That's where I'm going to step' — your foot is already moving. It's going to step there," he says. "You just need to trust in that."
• Think like a skier: Running down a steep hill in a straight line puts unnecessary strain on your body. Instead, do as skiers do: slalom. "When you get on those steep downhills, bank off the sides of the trail — literally slalom off the trail," Zac says. "That'll spread out the muscle distribution and make things a lot easier."
• Keep steady arms: You'll feel more in control if you keep your arms close to your body, Golden says. That way, you can steady yourself as you fly down the mountain.