Human tissues have more in common with rubber and concrete than you might think. Similar to these materials, if we apply too much force to our muscles, ligaments, tendons, or bones...they will break. The age-old question of "how much force is too much" is complicated by the fact that every person has a different threshold for what their body can withstand. Additionally, our tissues are constantly regenerating or "healing" themselves, and sometimes loading actually helps this process along. However, what we do know is that when the damage we are causing to our bodies outweighs the speed at which our body can heal, we have a problem...and oftentimes this damage is happening on a level that we can't even detect until it is too late.
Since physical loading is such a big component of understanding the progression of spine and other musculoskeletal disorders, we have spent decades building modeling tools and techniques to understand the loading on the human body. The logic goes that if we can understand the loading people experience and we know the tolerances at which their tissues start to break down, we can intervene before permanent damage is done. We use this knowledge both in our injury prevention efforts, as well as when assessing the best treatment options for our patients.