He had fallen backward and landed directly on his glutei maximi, obeying the law regarding equal and opposite reaction and several other laws involving falling bodies.
The muscles about the scapula, and the dorsum of the ilium (the glutei) were converted into great masses of bone, equal to the original muscles in thickness and bulk.
The trouble with your generation was that all they wanted to do was sit around on their glutei maximi and be entertained.
The chief physiological antagonistics of the glutei are the quadriceps femoris and tensor fascia lata.
