I have started running bare/minimal this March and I have never been a serious runner in my life. At first my calve and shin muscle grow tired first which is common. Now I am running around 5K each run and 3 times a week. The lower leg muscles are okay now but my glute muscle always protests at around the 4K mark. It is not painful nor stiffened up. Just feeling strengthless in the muscle. I feel that the more I bend my knee the faster my glute goes tired. It is a common case too? How can I strengthen it?