Headlamps can be dangerous because the shadows are in the same plane as your vision. I gave up using them for hiking because they didn't help me see drop-offs. You're better off with a light in your hand or on your waist.
After spending hundreds of hours hiking by headlamp, both on- and off-trail, I disagree. Sometimes it helps to hold your headlamp in your hand if you're running, but at a normal walking pace, it's not a big deal.
Ultratrail runner here. No-one in the ultra community uses handheld torches. We all use headtorches, and we run long distances at night through mountains
Does not change the fact that the light source is very close to the observer, and to make it worse higher than the observer. Both are quite bad for detecting the structure of the ground.
Torso would probably be good, any deeper and you get too much shadow in depressions or behind bumps, dosage matters.
But you lose head aiming into curves, so maybe somewhere in the jaw region might be interesting. You'd need an entirely new approach to fixing for sports that don't already have full face headgear, but the usual forehead position isn't exactly fashionable either (historically this position comes from mining I think, where the shadow/structure effect isn't wasted when it works on the ceiling instead of on the floor).
