I'd worry about sprained ankles on a false step or a slippery leaf-rock trap. Is there a technical approach to running in these conditions?

You just get used to trail running over time. If you’re nimble and light on your feet a slip almost never turns into a fall. With practice you dodge the bad steps without much thought or you step knowing it’s iffy, slide and keep running. You don’t commit hard down on your heel.

The form i use basically the “natural” running style. Land with your body over your foot, land on your foot flat or on the ball. This is good for trail running because it’s much easier to not commit to a step when you’re not planting hard with your heel.

I’ve never sprained an ankle trail running, not that it can’t happen. I’ve gone like 90 degrees on my ankle before but I can usually unweight and collapse on that leg and catch myself on the other leg and keep running. I run in sandals and I backpack in trail runners.

Trail running strengthens your ankles what with all the uneven ground that has to be compensated for.

For me the biggest insight was that there is no rule I have to be “running” 100% of the time when trail running. If some part of the trail seems sketchy it’s totally fine to just slow down there and do that part carefully. Then speed up to running again on safer parts.

You’re still getting almost all of the cardio benefits, and over time you’ll get more comfortable going faster on different surfaces, just from practice.

I've heard it's actually beneficial for your ankles long term to get some tilt/pan on them. It reduces your chances of injury by strengthening the twitch muscles in your ankle and legs.

Important to note the point is "trail running" not "alpine running", gravel and dirt vs, steep inclines and big rocks.

Anecdotally, just adjust your pace/length until you're comfortable. I've always done mixed asphalt/dirt-trail and there is a notable difference in my knee fatigue when there is a bigger ratio of one or the other, would always prefer a nice gravel or dirt over the road.

OP here. I've fallen many times, but never sprained my ankle. Usually if I have an injury from a fall at all, it's that I've skinned my knee or the palms of my hands (you can wear fingerless leather gloves if you're worried about that).

I have had two injuries that required medical attention. Dislocated my pinky finger once.

The other time I was crossing a wet wooden bridge. On the down-slope of that bridge, my feet went out from under me and I fell on my back. It hurt, so I walked a mile or so back to my car. Hadn't gotten better after a few days, so I checked in at an ER. Turns out I had cracked a rib, and that had caused a small pneumothorax. I was in the hospital for three days while they suctioned it and waited for the lung to heal. (The MD was amazed at my ability to breathe well despite everything.) When I come to that bridge now, I change to a walk.

many people try to go too much around puddles, bits of mud, rocks, ... Switching direction is what makes you slip/fall.

Sometimes, you should just focus on going straight, or at least keep your center of mass relatively going in a smooth line.

Yes, sometimes that means going through a puddle or do a small jump, but I find it much safer. Of course, on a potential slippery surface, try to make that 1 step lower impact, basically like an in-between step. This can also imply vary big changes to your cadence, which is not always optimal from aerobic perspective.

You can exercise your ankles so they are less likely to crumble if forced into an awkward position. Also look at where your feet land compared to each other: if one is almost ahead of the other (think camel stride), your foot is to the left (or right) of its hip and is thus naturally bent outwards. Having your foot land more squarely compared to how the body weight works, reduces the strain on the ankle. If the inside of your ankle/sock is always dirty after a run, this is why. Am currently going through the process of fixing this on myself.