Definitely do, otherwise no cricketer can clear 80/90 metres or bowl quick.
But, I think biggest problem with PAK players is their diet - most of them take too much oily food, sugar & red meat; which makes them strong but heavy as well. Besides most player is carrying few kg more because of oily food & their stamina is low - don't do the odd job, that is mother & father of all exercise - running & swimming.
Genetics, I don't think has anything to do in it - once PAK had some of the best ever squash players, a game which needs the highest amount of stamina, agility & flexibility; almost same is field hockey & volleyball. In fact, apart from fast bowlers, physical demand in cricket is less than most sports - interestingly, PAK has produced some of the fastest bowlers; it can't be genetics.
What current PAK players are missing is something Khan or Javed didn't - selfrespect & shame. Khan used to bat at 4 for Sussex, batting around 2000 overs in a summer, then he used to bowl fast for another 1000 overs in all formats. And almost equal numbers in nets - he could survive almost 20 years; so, it must not be genetics.
If Imran had the physique of Sarfraz or Umar or Sharjeel; I am afraid, watching himself in mirror, he would have committed suicide in shame - current PAK players 'dil khulker' smile after dropping a catch, as if it was a good joke.
Genetics doesn't have anything in that - you need to fill the pinch of inferiority complex that in your profession, you are 2nd class in a basic skill set; that day lots of those paratha, mithai, beef boti, mutton biriani, paya, bhuna kaliza 'll not enter through your throat.