What a Strong Core Really Looks Like

Think of a 180-kilogram sumo wrestler. "Nice abs" probably doesn't come to mind. That's because most people associate a strong core with a six-pack. But the truth is, it has nothing to do with muscle definition. "These larger athletes have loads of muscle, despite what you can see", says Sue Falsone, a clinical specialist in sports physiotherapy and a Nike Performance Council member who specialises in recovery. "They're good examples of how you don't have to be lean to be strong and powerful".

Your core is actually made up of at least 30 muscles. Giving an exact count is tough because some experts include the diaphragm and pelvic floor, and even the lats and pecs. (Defining the core is a widely contested conversation in the fitness community.) According to Ajit Chaudhari, PhD, a professor of physiotherapy and the director of the Ohio State University Clinical, Functional and Performance Biomechanics Laboratory, these are the main players everyone agrees on:

1. Rectus abdominis
   This is the long abdominal muscle that runs down your belly and allows you to pull your ribcage and pelvis towards each other for sit-ups as well as total-body movements, like throwing, running and jumping. It's known as the "six-pack muscle" because bands of fascia, the cling-film-like connective tissue that surrounds your muscles and organs, divide the muscle into six, sometimes eight, sections. (Sidebar: You likely already have the definition; whether or not you can see it depends mostly on how much fat is on top of this muscle.)
   
2. Obliques
   On either side of your rectus abdominus are your oblique muscles, both internal and external, or your "side abs". These allow you to rotate your trunk when you do, for example, a diagonal sit-up.
   
3. TA and QL
   Underneath the rectus abdominis and obliques are the deep core muscles in the front and back, including the transverse abdominis (or TA), which acts kind of like a corset and is your deepest core muscle. It compresses the abdominal cavity and increases tension in the fascia so you have a stronger "web". Then there's the quadratus lumborum (or QL) on either side of your lower back, which help stabilise the entire spine when you bend to one side.
   
4. Erector spinae and multifidus
   The erector spinae are the muscles that are most visible in your lower back, and they help you extend as well as bend laterally. The smaller deep muscles of your lower back, like the multifidus group, are tiny muscles that run from the area up to your skull. They help extend the lower back and help stiffen the spine to resist bending.

The other muscles include your psoas major, hip adductors and abductors, glutes and more, but those are more involved in the function of your lower body than they are of your core, well, core.

"If you think of your body as a wheel, the core is its hub", says Falsone. When you're strong and stable in that area, your arms and legs, or "spokes", can produce and absorb force really well. Running feels easier because your legs aren't taking on the full impact of pounding the pavement. Your forehand has serious power because your arms aren't the only things generating strength to swing the racket.

A stable core also means that your hub has the muscular control to let your spokes move without compromising your spine, says Falsone. Take the cable chop, a rotational resistance exercise that mimics the forehand mentioned above: If you have core stability, you can pull that cable in a smooth motion using your shoulder and arm muscles while your spine stays put. Without that stability, though, you could twist your back in an unsafe way or be unable to do as many reps, because your arms are taking the brunt of the work, says Falsone.

A weak core can put you at risk for lower-body injuries too. A recent study conducted by Chaudhari found that novice runners who didn't have sufficient core stability were at a higher risk for developing knee issues. "If you don't have core control, you are going to be more likely to sprain your knee or roll an ankle", says Chaudhari. That's because you essentially have a big wobbly mass that you have to manage with your legs instead of your core.

You might have heard by now that the best way to strengthen your core isn't by doing endless crunches, which Falsone says are often performed incorrectly and aren't healthy for the spine even when they are done right.

Total-body exercises, unilateral (or single-leg or -arm) ones in particular, are a lot better. "Lunges, especially if you hold a dumbbell in one hand, activate your core muscles", says Falsone. "Even a single-arm bicep curl introduces a small element of rotation that your body has to stabilise against". Look for a workout programme that incorporates unilateral training regularly.

Beyond that, a little dedicated core training definitely goes far. According to Chaudhari, a great way to start is by spending only five to 10 minutes on just your core three to five days a week. "Most people don't have great core muscle endurance, so a few minutes most days can really help", he says. If you do happen to have that elusive endurance (congrats), or that work starts to feel easy, double that time.

To begin, try the bird dog. From all fours, lift one arm and the opposite leg until both are parallel to the floor, and hold there for up to a minute. You could also do a dead bug: Lying on your back in a tabletop position, extend one arm and your opposite leg until both hover above the floor, then switch sides and continue alternating. You can also do planks, side planks, leg curls on a stability ball and ab roll-outs.

Even if you don't see those "nice abs" right away, you should still notice them pretty quickly—in the form of better, stronger workouts and more comfortable movement all around.