You need strong legs for trail running, and your strength training should be planned around hills, because both uphill and downhill running require a bit of muscle.
“If I was doing two strength sessions a week, I’d have one that’s predominantly focused on training for running downhill and one on training for uphill running,” says Evans. “They would be separated throughout the week so I wouldn’t do a hard downhill run followed by a downhill strength session. I might do a hard downhill run, and then the next strength session would be an uphill strength session. Then after I’ve done a hard uphill run I might do my downhill strength training.
“Downhill is all about your quads. It’s about time under tension and knee stability. Do eccentric work, like a rear foot elevated lunge, for example. You can start by doing it isometrically—just holding the position—so you’re getting maximum time under tension.
“For uphill, it’s all strength and power development, mostly from your posterior chain: your glutes, your hamstrings and your calves. Do regular squats, regular deadlifts and regular calf raises. I go pretty heavy—five sets of five reps would be typical.”