Originally posted by HandOfFateI'm pretty sure that when AM or Vixen manifest a power, they gain sufficient durability/stamina to handle said power without causing harm to themselves.
Which would probably happen without a higher form of durability to support his super-strength.
That's why Vixen can conjure the speed of a cheetah, for instance, and not shred every muscle/ligament/tendon in her legs when she starts running. Etc.