me and my friend have been working out for about 3 years..
ive always done the traditional, 3-4 sets for each muscle group yadda yadda yadda..
main problem i see with him is, he comes into the gym, warms up with 50lb dumbbells, then goes straight to 100lb dumbbells for shoulder press, so it looks like this.. 50, 100, 90, 80, 70, 70, 70 (then goes for upright rows, or lat raises, etc)
NOW, what i do, is i warm up with 50, then go up to 80, than 90, than 100. each with reps of 6-10 reps. then im done , 3 sets!!! WOO (not including warm up)
then i do lateral raises, and then shrugs, and im done shoulders.. and hes still goin at shoulder press!?
now, if i am correct, your tendons and ligaments strengthen SLOWER than muscle does.. thus why it takes years to lift tremendous amounts of weight without injury. its why you see guys with world records and they are 35+ years old. YES they have years upon years of lifting under their belts, BUT its because there tendons and ligaments have gotten stronger throughout the years.. also with getting muscle also!
but heres the dealio, i personaly think my friend without proper warm up , will someday come upon a weight where he will do say:
150lb dumbbells(hypothetically speaking of course)..
and then POP! goes a tendon or ligament.. out for 6 months..
correct me if im wrong..