The intent of core training is to strengthen the muscle groups that stabilize your skeletal structure. These are primarily the muscles in the thoracic area that determine your posture in each sport and in effect link your upper and lower body. The muscle groups that you strengthen with core training generally don't have the range of motion needed to drive you forward, but they are the 'platform' from which your arms and legs work. This need for a stable platform clearly applies to proper running and cycling posture. In highly developed swimming movements it may be even more important since the middle section of your body can actually contribute force through twisting motions where the direction of force from arms and legs oppose each other.

Core training helps get you 'in touch' with individual muscles and small groups of muscles. This awareness of specific muscles, or muscle groups is the first step in improving various posture and form issues. For example, many adults (and plenty of athletes) have poor posture stemming from weak mid-back muscles (rhomboids). This particular posture issue looks badly and can negatively impact each of our three sports. The first step to improving your posture is getting to know these muscles, then toning them so you can tighten them independently of your lower back's muscles which probably don't need additional toning work.

Core training focuses on muscular areas of the abdominals including obliques (your sides), upper and lower back (deltoids, rhomboids), hips (gluteals, hip flexors, psoas…), outer and inner thighs (abductors and adductors), hamstrings, even some pectoralis and triceps work.

When driving yourself forward in each of our sports, you're actually only as strong as your weakest muscular link. For example, even if you have the quads of a bodybuilder, you must have the strength in your upper body to control the force your quads can develop. On a bike, gravity dictates that all down force generated at maximum output is limited to your body weight and the opposing force of pulling up by the opposite crank arm. You can create additional down force by pulling up on the handlebar, thus opposing the tendency for your body to rise as you push down with your quads. But, since your legs are attached at your hips, not at your arms, the stable platform your arms create must be extended to your hips and legs through a rigid torso. Similar dynamic examples apply to running and swimming.

In running consider what you felt like during the IronMan's marathon (any marathon for that matter). When you become fatigued, your form falls apart. It's not just because of tired legs, it's tired arms, tired back, everything hurts. Having a strong torso helps hold your form together in the latter stages of an endurance effort - any distance race effort for that matter.

Now consider how a fish moves when it swims. Its fins and tail don't move independently from the rest of its body. The force a fish creates is through longitudinal flexion of its whole body. Non-aquatic creatures are the only ones that move with its appendages.

The movements below can all be done without any special equipment, just a floor with a little padding is all you'll need.

Here is a short sequence of core movements: