Slapped together an edit for you:
Moved the closest shoulder forward on stride for 2 frames, looks less stiff. I planted the sprite on the bottom of the image and noticed the feet seemed to slide along the floor, so I lifted the feet on the upsteps. I also swapped the furthest legs wholesale between frames 1 and 8. Slowed the animation down by increasing the delay by 1 fps per frame. The up & down bob wasn't consistent, so I fixed that too.
Something I didn't illustrate in my edit: the furthest arm's motion could match the other more closely.
Great job otherwise, the arm "breaks" look good too
PS I can't seem to fix the transparency issue your image is having