The Master Chief is a Spartan mk II super soldier and so has been augmented in a number of ways designed to increase battlefield performance.
Carbide ceramic ossification: advanced material grafting onto skeletal structures to make bones virtually unbreakable
Muscular enhancement injections: protein complex is injected intramuscularly to increase tissue density and decrease lactase recovery time.
Catalytic thyroid implant: platinum pellet containing human growth hormone catalyst is implanted in the thyroid to boost growth of skeletal and muscle tissues
Occipital Capillary reversal: submergence and boosted blood vessel flow beneath the rods and cones of the subject's retina. Produces a marked visual perception increase.
Superconducting fibrification of neural dendrites: alteration of bioelectircal nerve transduction to shielded electronic transduction. three hundred percent increase in subjects reflexes. Anecdotal evidence of marked increase in intelligence, memory, and creativity.