What is the “core”? Why should you bother about your core muscles at all?

In common discussions, the core of the body is considered to be the trunk or torso, or sometimes just the abdomen (which is why you see most exercises recommended for the core muscles are actually targeting only the abdominal muscles).
The core muscles actually comprise of all the muscles from your diaphragm down to the abdomen and to the bottom of your pelvis.
The muscles that can be included in the core are the pelvic floor muscles, transversus abdominis, multifidus, internal and external obliques, rectus abdominis, erector spinae (sacrospinalis) especially the longissimus thoracis, and the diaphragm, the latissimus dorsi, gluteus maximus, and trapezius.
Many of these muscles are deeper than the external muscles that we ordinarily target to train.

The concept of the “core” is better understood using images or video.

This image from the American Council on Exercise (https://www.acefitness.org) shows you all the muscles that are part of the core.

The video below gives a clear explanation of what your core is:

For those of you keen on a more academic but extremely enlightening anatomy lecture involving the core, the video below by Brent Brookbush is excellent:

You could say that your core is a complex of muscles extending far beyond your abs and including everything besides your arms and legs, and is involved in almost every movement of your body.
Now that we know what our core muscles are, let us look at what these muscles do.

Functions of the core

The human body is subject to various external forces, and the core muscles help the body with balance and movement while handling these forces.
A static posture like standing erect involves several muscles that must balance the weight of your body and gravity. Your abdominal muscles, the muscles on the sides of your waist (obliques), muscles of the lower back, the sacrospinal muscles running along your spine, your gluteus muscles, all work together to keep you standing.

In a dynamic movement a complex set of muscles must work in tandem and in coordination with the skeletal system to make the intended movement successful with balance and without injury. An example is walking on an incline.
The body has to resist gravity, create movement, and balance itself against the inclined surface. One could think that the movement is handled by the legs, but this is not so, because without the balance the pushing legs would simply make you fall down. First the core is stabilised, and then the legs move the core in the desired direction.
Now, suppose you introduce another, common force to this dynamic – a slippery ground.

You can appreciate the importance of a strong and quickly responding core to our day to day activities.
In fact the core is recruited in all day to day voluntary movements like running, pushing, lifting picking up a pack from the back of a top shelf, swinging that racquet to get the ball smashing to the opposite court, putting on your socks and tying your shoes.

The core also provides internal pressure for involuntary acts like expelling substances (vomit, feces), pushing that baby out in birthing, in stress urinary incontinence.

Core strength is the ability of the body to handle force fluidly with strength, balance and control.
This can be achieved by a well rounded fitness program that goes beyond just the abs and includes movements that include instability and engage the muscles of the core.