Running

Finally I'm only "firing" 3 out of the 4 hip flexors, this means that when pulling up (thigh toward body) I can only raise it my leg so far and then have to arch my back- which is causing me to cycle with my back arched and arms stretched out.

The dormant hip flexor is also allowing my femur to pop out of the socket, which needs to be resolved.

I have another exercise for this.

Could you explain this exercise? I've had hip flexor issues in the past and want them to stay away. Any other exercises/stretches I can do would help.