For a strong and functional midsection, train more than just your visible abs. Try these three exercises to get the most "value for time" when training rotational core strength.
1. Suitcase Carry
Sounds counterintuitive, but one of the best ways to improve rotational core strength is to train anti-rotational strength. The suitcase carry is an excellent unilateral exercise that crushes your transverse abdominis and obliques.
Make sure to resist lateral flexion by keeping your body as upright as possible, not letting the weight pull you down. You'll feel your core working in a whole new way while building strength and stability. Go for a set amount of time or distance, adjusting the weight to fit your needs.
2. Barbell Trunk Twist
What better way to train rotational strength than twisting a weighted barbell from side to side? This exercise activates basically every core muscle you have, making it an incredibly functional exercise.
Consciously flex your abs and obliques hard while twisting the bar. Pivot on your toes and keep your arms as straight as possible to avoid your upper body from taking over. Hit 3-4 sets of 6-10 reps per side with moderate weight.
3. GHD Oblique Crunch
If you have access to a GHD (or a 45-degree back extension machine), use it. This is much harder than it looks and smokes your obliques.
Set up lying on your side with your hip bone digging into the pad, feet crossed. This unorthodox set-up allows you to train with an increased ROM and really isolates the transverse abdominis and obliques. Three sets of 8-10 reps per side is a good place to start.