1
Force produced is not solely dependent on the size of the muscle. This is self evident if you watch sports, athletics or martial arts. Pudgy cricketers smashing the ball 100’s of meters away, lanky tennis players socking the ball, Thai teenagers punching harder than bodybuilders more than twice their weight. Force and size don’t go hand-in-hand. Size matters but skill takes you further. Only when skill is
matched, does size or fitness make a difference.  

2
Strength is task dependent. A strong throw  ≠ strong punch ≠ strong kick  ≠ strong squat ≠ strong jump. While there is some spillover, every skill or expression requires a distinct capacity, nuance control. Brute force does not result in precisely applied force. 

3
Strong muscles are not necessarily less susceptible to injury. The generic ‘strengthen joints and muscles advise’ is over simplistic. Our tolerance for positions, how rested we are, how much time we spend on individual positions, genetics, phased exposure to stimulus are all factors. 

4
You can injure or strain yourself even if you have ‘perfect’ posture. Conversely you can go years without feeling discomfort with less than perfect posture. Tolerance to positions is a spectrum not a single ideal. Your attitude to pain and movement goes a long way in how you adapt to it.