Can someone explain the superhuman strength part? How can it be that an average built male can basically become the hulk and require freaking 15 (!) cops to contain. What does the drug do to give this effect and why is the "unlocking" mechanism there. I know you get a lot stronger when you're really angry but not to this extent. Is there some type of substance that only kicks in when your life is in danger or? Are humans "capped" in terms of strength, and if so how much?
As mentioned, humans subconsciously limit their strength. There are some rare exceptions though, such as "Retard Strength", where a mentally handicapped person is subconsciously using FAR more power than they're aware of.
Another exception is adrenaline kicking in and actually "becoming the Hulk" so to speak, to overpower yourself out of a situation. Best example I got of that one was some dude who was able to overpower 2 taser shots by ripping them out while getting shot trying to escape from the cops. Needless to say, that ended in fatal results as he died of exhaustion. Though in terms of Mortal Danger, I'd imagine you'd use everything you have to try and get away, no matter the consequences.
Some stuff I found searching around:
Its believed to be to a normal human can only using a certain % of his potential strength. Our bodies have a "limit" so to speak on actual strength. It is a safety devise to keep humans from using all their potential and injuring themselves and all that. Mentally handicapped people don't have that "cap or limit" as much as the average person does.
Explains superhuman strength during adrenaline rush
Explains why humans can jump 30 feet when electrocuted (yes when your electrocuted your muscles firing off so fast are what cause you to fly in the air, not the electricity)
Explains why one human can be much stronger then another at a same body composition
To an extent, if you didn't have that limiter in place, you wouldn't last too long probably.