Transitioning from treadmill to outdoor running

that's because you aren't really "running" on a treadmill...you are keeping up with the belt which is totally different than propelling yourself forward.

Try music to keep pace...maybe use the C25k App to work up to it.

It is different. On the treadmill, you have the motor and the belt dictating speed and providing the propulsion. As a result, you're not propelling yourself as much as making sure you move your legs fast enough to not be thrown off the machine. On the trails, it's ALL you. You're in charge of maintaining speed (which isn't as constant as when you're on a treadmill). And instead of your energies going to moving your legs fast enough to keep up with a moving belt while supporting your weight in an upright position, the focus is now placed on moving your weight forward.

When I transitioned, I found that the treadmill work had helped condition my cardiovascular system, but I had to do more training to get the rest of my body into the game and acclimated to running "unassisted". One of the big changes for me, other than having to manage my speed, was that my best gait for running is almost impossible for me to use on the treadmill without kicking the motor housing. So I think the best tip I can provide is to let yourself run at a slower speed than you used to do on the treadmill. That way your body can get used to all the new tasks it has to manage.

It takes time but it's different. On my treadmill, it takes me a long 52-54 mins to do 5K and I feel like I'm running fast. Outside, I can now do a 5k, at a pace I though was a snail, but generally finish in around 39-42 minutes, even with long slow uphill parts and walking the first 5 mins to warm up. I'll never be speedy, but I'm doing it. I can go longer on a treadmill, up to about 7K, but pacing outside feels better, as I choose, rather than conforming to the belt speed which I feel is too fast.

Just getting outside was my biggest challenge. First time outside, I only managed less than half a mile, then realised I was going too fast and my feet hurt. My next run, I slowed right down and could keep going. I don't believe the treadmill is easier. It builds endurance. What we then do is gradually transition that to the differences outside. You begin to get used to it after a few runs. I was very embarrassed the first few times and would only go out once it was dark. I don't incline for a whole run on treadmill as then I find it difficult to run on the flat outside as uses different muscles and I notice it. Wind resistance doesn't bother me if it's light.

I'm a mid foot lander, on treadmill and outside, and I suspect it's easier for us to transition than a heel striker.

Shoes make the difference too. Treadmill is often more bouncy but our feet take the shock outside. I switched to max cushioning for outside and found my 5K achievable after two runs. I went for Saucony Triumph ISO 2. Exp but worth it as I have fibromyalgia. The first run with them was intervals of walk/run to break them and me in. It's still tough, but I can do it.