The fact is that your ab definition will relate more to your daily nutrition than your exercise routine in the gym.....
However, if you are going to do the best possible abdominal exercises to get great definition once you have removed body fat around the torso then the most "effective" exercises are an important consideration when you are busy and time poor.
It's important to understand what the term "effective" means though when it comes to exercise. It's not necessarily "feeling the burn" or "vomit inducing." In fact "effective" means doing as many as you can do until your exercise form stops you doing the exercise well. The Turkish Get Up is one such exercise, which involves multiple muscles around the torso and shoulders.
Considered by some as a "functional" exercise (a misnomer because all exercises can be "functional" for a specific task) this exercise we highlight as an "effective" exercise as it involves a multitude of movements and muscular contractions working your obliques (sides) and main abdominals. Indeed it's probably the first movement you perform daily when you get out of bed (perhaps without your hand punching the air).
What are the advantages? Not only will this exercise make you look more awesome than your training partners in the gym it is a great assessment tool for abdominal strength.
Here comes the science bit... It's a good test exercise as it will show side to side discrepancies in strength and muscular balance, it challenges rotary and linear stability, single leg hip stability as well as shoulder stability. In all it is a pretty challenging exercise with a multitude of benefits.
We use half Turkish Get Ups with a lot of our new clients at Results FAST. Initially we start with the basic rolling movement demonstrated here.
This exercise basically works the torso intensely so is a good starting point for beginners. You do not necessarily need the extra weight but it is good to load this movement before progressing to the next level.
On the next stage we can progress in to a bridge movement challenging hip strength and stability.
The full Turkish Get Up follows here where we take the exercise to standing, at this point we also challenge the lower body as well as stability through the torso and shoulder.
There you have it. If you are going to perform one exercise for your torso than maybe this exercise is the one that will challenge you in a multitude of ways and not only makes you look great but also will earn the respect of your training peers.