Superhuman reflexes is the biological ability of a DNA Alternate to increase the speed of nerve clusters firing, allowing them to react to stimuli faster than a normal human's capacity allows. The Alternate can dodge bullets, catch flies mid-air and normally react instantaneously to what others take more time to react to. The Alternate can dodge fists easily, reacting to the punch as the attacker is still preparing it.
With such a super-charged nervous system, the Alternate can easily dominate close-quarters combat. They are described as untouchable because they are faster than anything coming at them.