What I expected to happen was...:
getting knockback

What actually happened was...:
getting knocbake and losing hunger

Steps to Reproduce:
1. use this command:
/give @p minecraft:bow 1 0 {ench:[

]}

2. change gamemode to survival

3. hit yourself at least 4 times
make sure you have a lot of space
flat world is advised

4. sprint for a bit