HOW TO GET HURT
Basically injuries occur when you're subjected to loads that you're not conditioned to handle.
LOAD here is defined as the total amount of work you do (volume x intensity) as well as how tough it is (rate of perceived exertion).
You can experience a single event of a massive fucking load, which will result in immediate structural damage, as the capacity of your tissues is exceeded. This is called an overload injury.
You can also experience a so-called overuse injury as a result of a series of accumulated loads that are either slightly above your tissue capacity, or if there are simply too much and you recover too little. These are the kinds of pains that sneak up on you.
Overuse injuries are much more common than overload injuries, and overload injuries oftentimes have an overuse component, meaning that your body has needed a deload for a while, but you ignored this and now it slaps you right in the face.
Now, how BADLY you get injured depends on how big this load is compared to your individual capacity (and sometimes just poor luck). If you can deadlift 315 with good form and you're pretty well recovered, you're quite unlikely to snap your shit up trying to pull 320. If you've really been pushing the envelope and need a deload, lifting even half your max CAN hurt you (won't necessarily).
Certain factors influence how well you can tolerance load. For example your lifting technique can help distribute the load better, so you can handle more of it.
If you're stressed as fuck or tired, this makes you tolerate less load.
This is what SCIENCE says about how injuries happen. If you want to learn more, look up research by Tim Gabbett.
It's not the exercise that hurts you. It's how YOU choose to approach the exercise. Any exercise can be potentially harmful, and any can be safe. Yes, too much stress (load) can hurt you, but at the same time, stress (load) is exactly what we need to become stronger and more injury resilient. IT'S ALL ABOUT THE DOSE.
