Trail running—especially in mountainous terrain—is more complicated and challenging than monotonous pavement pounding. If you’re transitioning from roads to trails, don’t expect to run at 100% right away. You’ll need more focus to dodge obstacles, and different conditioning to handle varied terrain. That’s what makes trail running fun, so give yourself a break. Maybe even hike the nastiest switchbacks. No one’s judging.
Avoid the urge to hunch forward and curl into a sad running ball. Keep your back straight, and let your ankles adjust to the incline. Maintain a compact stride underneath your hips, lengthening your arm swings to propel you up the hill.
Avoid slamming on the brakes during steep downhill sections. Fighting gravity puts strain on your muscles and can throw you off balance. Keep your arms out to the side, and don’t worry about flailing a bit to maintain balance—looking weird is better than tumbling ass-over-teakettle.
If you do fall, go with the fall rather than fight it. If you roll with gravity, you avoid stiffening your limbs and potentially injuring yourself further.