At some point most people will have back pain in some form or another. Most people have a disc injury at some level even if they have no pain (Jensen et al. 1994). This study used MRI's of people who had no back pain and only 36% had no issues at any level in their disks!! Knowing that 80% of people experience low back pain, it is extra important to make sure that you move well so that you don't experience pain. If you have pain get it checked out by a medical professional quickly. The sooner you get a diagnosis the sooner you can get back to chasing your goals.
This is not ideal
A good rule of thumb to follow is that if it hurts don't do it. With a potential for back pain following that rule is especially important. There are 3 major pain triggers for those with a potential disc issue.
How do we train around this? We need to use exercises that encourage more extension.
Homer getting some extension to improve his flexion intolerance
Now this doesn't mean that everyone needs more extension. Too much extension is bad and has its own not so fun consequences. This is for people with a flexion intolerance.
Most of our training should be done standing up. For most people with disc injuries the pain is primarily when they sit down which is usually in a flexed position but decreases with standing which is more extended. If we follow the rule that if it hurts don't do it, we should do less exercises seated and more standing. This will help avoid one of the major pain triggers and hopefully help to stay out of unhealthy positions for the back.
Crushing heavy squats might have to be put off for a little bit to help the back feel better. However, this does not mean that you need to avoid training legs. Adding single leg work can be great to help decrease the loading required to get a good workout. Initially using sliders might be the way to go because the stability needs are so high that you can't use as much weight, which will help spare the back. Generally the more challenging it is with less load, the better it is for this population.
Use more exercises that have the hands above the weight such as 2 Kettlebell racked position lunge. Using the racked position for the lunge helps keep the back more extended in addition to sucking enough to not require as much weight as holding the weight at your sides.
For core training it is time to ditch the sit ups and get some more low back friendly exercises. Sit ups are repeated flexion of the low back, and repeated flexion is the primary cause of a majority of disc issues. In particular ones that get the hands going above your heads. Exercises such as Dead Bugs, and Suspension Fallouts work great to get strong in a healthier posture. Pallof Presses and Anti-rotation Cable Chops also work great to help get strong resisting rotation in the low back.
Often just getting up and moving around more will help decrease the frequency of pain. Walking is one of the best exercises for many with low back issues. This could be as simple as getting up and taking a lap around the house every hour and then increasing the distance or the frequency as you begin to feel better. If you ever feel pain, then stop what you are doing and rest. Working through pain rarely gets anyone very far. Work around pain and eventually you will be able to do more activities pain free.