Paloff Press for a Strong Core and Happy Lower Back
/If the bulk of your core strengthening work consists of sit ups, crunches and other core flexing moves, consider doing more core stability or anti-rotation exercises like planks or this move called a Pallof Press.
When at the gym I have clients do this using the adjustable cables like in the video below. But you can easily get the same benefit using a light or medium resistance band tied around a pillar or door knob like I show in the picture below the video.
The trick is to pick a resistance that challenges you while still allowing you to move with symmetry and good posture (hips level, shoulders down, pelvis tucked).
Start light with 2-3 sets of 12 reps each side and build. You will feel this all over especially in your core and glutes. These are particularly good if you have lower back issues and likely a safer choice than sit ups.