It seems that this is either a bug or someone has interfered with my account. When I hit another player or player entity (not so with NPC's such as villagers) with a melee attack while I am sprinting using the sprint key (not double clicking W), sprint will momentarily glitch causing me to briefly hesitate as if sprint had turned off then turned back on. This is a very brief hesitation but it causes me to fall behind in my chase of the player as my speed has been affected. I notice this when I am trying to strafe around another player as well. Also many times the hits will not register with the server. I have tried this on several different servers.