I know this is more than just one exercise, but have you all tried the new Les Mills Program CXWORX? It is a 30 min workout in a Group Fitness setting or a small group PT session. CXWORX really hones in on the torso and sling muscles that connect your upper body to your lower body. If you haven’t heard of it yet, check this out…. http://www.getcx30.com/
I love Russian Twists! Done correctly, it’s an excellent ab exercise that usually gets results quickly for a lot of people.
I like to think of it as a versatile exercise as well. There are a lot of variations that, as a trainer, I am able to use with my clients. By adjusting the angles, the tempo, and the resistance used or not used, you end up with an all around great exercise!