I love expanding my horizons and when I read a new expanded definition of the core, I was quite pleased. I generally think of the core as the abs, pelvic floor and muscles on either side of the spine. According to sports medicine specialist Vijay Vad the core is not limited to the area around your belly button, but is really everything between your "nipples and your knees."
The abs, especially the deep abs, the pelvic floor and the muscles on either side of the spine all work to stabilize the low back (lumbar spine) and the pelvis. All the thigh muscles, which attach to the pelvis, can seriously affect the alignment of the pelvis. Tight hamstrings or tight quads are often the culprit, so keeping flexible legs is vital to the health of your core. Another important muscular component is keeping the obliques, the abdominal muscles you work in the bicycle move, strong as well. They help keep the rib cage aligned over the pelvis. If the rib cage gets out of alignment the low back becomes vulnerable to injury too.
From now on, when challenging your core think about connecting your torso all the way from your nipples to your knees!