You will never outrun a bear, no matter how hard you try! Bears can run both up hill and down hill it they wan to and this falacy that they can't run down hill is just a myth. Black and brown bears can out run a human on any terrain and although many will tell you that if you see a bear, you should run downhill, don't try it!
If you do encount Hair Bear Bunch, back away very slowly and try to keep more space bewteen you and the bear. If there is a tree available, climb it! However, bear in mind (no punn intended there) that the bear can also climb trees! Black bears can climb well, but grizzly bears can only climb short distances. If you have to climb away from a bear, make sure that you climb at least 33 feet up. This gives the bear less chance to pull you off. Once up the tree, most bears will retreat because they don't particulary like tree-climbing. Once the bear has given up, only come back down the tree when the coast is clear.
If you do encount Hair Bear Bunch, back away very slowly and try to keep more space bewteen you and the bear. If there is a tree available, climb it! However, bear in mind (no punn intended there) that the bear can also climb trees! Black bears can climb well, but grizzly bears can only climb short distances. If you have to climb away from a bear, make sure that you climb at least 33 feet up. This gives the bear less chance to pull you off. Once up the tree, most bears will retreat because they don't particulary like tree-climbing. Once the bear has given up, only come back down the tree when the coast is clear.