i think warming up is something people really miss.
part of working out is the hormone responce and cell signaling in order to do that you have to get yourself moving and mantane it.
i either walk or bike for 20-30 mins prior to the point where i start sweating. i dont count bpm just go by feel but sweat needs to start dripping prior to really hitting it.
after that if it is a weight session i use a stick or pole in my hands and slowly open up arms and shoulders with full range movements, then go to a sort of dc stile broom stick stretch super slow and bring it all the way down to the floor like stiff leg dl 20x.
ab work
then weights
all weight sets i start super light bar or tiny dbs to get the movement and work up to work weight.
training is followed by 20 min cool down walk or bike to bring hr back down.
if its just cardio i still do 10-15 min warm up and 10 cool down with real work in the middle.