In my time at the gym I have observed guys who deadlift 400+ pounds and bench press 300+ pounds but when asked to do push ups and pull ups they can't even complete 10 reps of them.
I have also observed the opposite where guys can do an unlimited amount of push ups and pull ups until they are blue in the face but can't lift heavy weights.
What distinguishes the difference between the said muscles being used during each exercise? For instance if you take an exercise that mimics or is similar in nature to pull ups such as a lat pull down or the bench in comparison to push ups, what differentiates the movements and causes such a difference in strength between the exercises. Does gravity come into play? Maybe different stabilizer muscles are being used?
My second question is in regards to the proper timing and frequency of performing body movement exercises. I usually start my back days with wide grip pull ups using body weight and then finish the day with assisted wide grip pull ups and with chest I start my day with several sets of push ups to get my chest warmed up and will sometimes end the day with more push ups.
By performing these exercises am I fatiguing my muscles to much prior to performing big lifts such as deads and bench? If one was to perform variations of push ups and pull up should they have their own committed day away from weights to perform these exercises? If so, how frequently can you perform push ups and pull ups without interfering in the process of allowing your muscles to heal from previous exercises to that muscle group? Every other day or every couple days?