Just speaking from my knowledge of anatomy , the running analogy is true because of fasttwitch and slowtwitch distribution throughout the body everybody is born with different amounts of fasttwitch and slowtwitch muscles throughout the body . Training can give you more stamina and power , but we are all pretty much born with a limit . I believe that pain tolerance has to do more with nerve impulse . Correct me if I ' m wrong , but from my understanding nerves can influence each other and decide whether to send an impulse to the central nervous system or not . Basically , if the number of nerves that want to send a signal to the brain outweigh those that do not want to send a message to the brain , then a message is sent to the brain and vice versa . I thought you could also form new synapses between nerves , which could possibly be why people have different pain tolerances , but I ' m not sure if you can do that for the peripheral nervous system .