I am in the middle of SL5x5, breaking PRs (not impressive at all, but rewarding for me) every week and it feels great.
However, my lower back is taking its toll and I experience more and more lower back DOMS, and more and more stiffness.
My core is not very strong and I would like to know what would be good for it.
I searched on the articles and I got tons of different exercises but it’s very difficult to make a choice… Something simple I could do at home rest days would be fine I guess.
Once you know how the abs and obliques feel when you brace them from the movements Reed mentioned, practice bracing your core as hard as possible with light weights doing front squats and stiff-legged deadlifts, the main focus is your core for these lifts not how strong your hams or quads are. You should feel them being tight and if not then you still need more practice learning to fire them. Doing those movements will help you transition to bracing your core for the squat and deadlift.
Although you’re hitting PRs right now, I would recommend for a reset using a training max that takes about 4-6 weeks to get to the same point. Continuing to lift at high intensities will only continue to reinforce bad habits. The weight needs to be light if you want to change your technique for good and to allow time for your abs to catch up to the strength of your lower back. If you do it right you’ll blow past your old PRs without frying your lower back.
Since you’re a beginner, I would advise getting your technique looked at as well. Make sure you have a proper setup and the right muscles are activated, especially the glutes.
I do the Anti-extension movements with a band suspended in my closet. Add some rollouts and I get a nice home core workout for my off days.
Also, take a deload week. That’s not lower back DOMS, it’s lower back pain. You need to work on form, mobility, and core strength or you’ll get hurt. Do you want to get stronger for a few more weeks and then take several months off while working with a chiro, or would you rather back off now and keep making great progress over the long term?
Strengthening your core through isolation movements is fine but eventually you will want to incorporate core bracing into a full kinetic chain movement. Paused front squats and stiff-legged deadlifts with light weights are great training tools to teach you exactly how the torso should feel during the squat and deadlift and in addition they require the core to work harder. These can be treated as core exercises as well. I have never felt my core work harder from paused breathing front squats (take up to five breaths at the bottom to relieve intra-abdominal pressure to really make the core work).
Once you have learned to brace your core for the squat and deadlift then simply doing isolation work is fine.