Core training is the most universally appealing desire of mankind. Whether you are a mother, an older gentleman, or a professional athlete, we cannot resist the temptation of abdominal work and its promise of injury prevention with a six pack abdomen. The tricky part is that this trunk area connects your upper and lower body, so it is involved in pretty much every movement beyond sleeping (see Sparta Point 4/1/09). So then what we are really searching for is efficiency. Where can you get the most activation and benefit for your core in the least amount of time?
We define core training as the development of the deep and superficial muscles that stabilize, align, and move the trunk. With this perspective, you can see the benefits of core training are mostly injury preventative in nature. If you want a smaller waist and those chiseled abs, nutrition is the chief component (see Sparta Point 12/16/09).
As far as recruiting the most core musculature, traditional weightlifting exercise, particularly the squat, have much greater core activation than any other movements (see Sparta Point 6/23/10). This high recruitment arises from two major aspects; the heavy weight and a standing posture. You do not need a research study to explain that heavier weight challenges stability and its associated musculature more than a lighter weight would. The second component, a standing posture differs from traditional planks or floor exercises due to an upright pull on the pelvic musculature. Because the core muscles run from your upper body to the legs, usually inserting on the pelvis, standing postures will have a much more global, widespread stimulus on the core.
Fortunately, squats have a huge demand on your body so other movements must be included if you train more than one exercise a week. But we are all pressed for time, so what could we possibly add differently that includes both weight and a standing posture. Try walking.
Stuart McGill, a professor out of the University of Waterloo, examined the effects of strongman events on trunk activation. Strongman events often mimic these hunter/gatherer activities with movements like sled drag or suitcase carry as shown below. This 2009 study found muscle activation peaked in the rectus abdominus and obliques in all of the events, up to 65% greater in the walking phases! The authors went on to describe the overload of the hips in the lateral plane (left to right), which maximally recruited the abdominal muscles to brace for spine and pelvic stability.
So these loaded carries can maximally recruit your abdominal muscles like a squat, but also in different planes. We use these movements once our athletes have maintained adequate upper body strength, when males can do at least 16 pull-ups and females 6 pull-ups, to allow these movements to target the abdominal muscles rather than be limited from upper body fatigue.
Load up the weight and walk tall for maximal core stability, but if you are not performing squats or pull-ups, you missed a spot.