I do trail ultramarathons (100+ mile trail races). If you're seriously looking for a pack, look at Salomon, Ultimate Direction, Nathans, and UltrAspire. They make some good ones that I've used in 100 mile mountain runs when I'm not going to see an aid station for a solid 30 miles or something like that. If you're really looking to carry stuff and run, that's the way to go.
They also make those stupid fanny packs.....
They also make those stupid fanny packs.....