Core stability has become the new 'buzz' word in the gym. Most of us equate a strong core with a well-toned abdo-men and supple waist. What isn't well understood is how core stability is essential for preventing injury.
Core stability is 'trunk dynamic control', which refers to all muscles of the trunk-front and back-encasing the spine within abdominal muscles, the hip muscles running into the legs and muscles of the buttocks. A strong trunk stabilizes your entire body, increases your ability to move with greater control and helps to keep an aligned posture when you move.
A strong core affects every other muscle group because movement is dynamic, continually changing from one muscle group to another. If fact, when leg movement is studied, it's the muscles of the abdomen and core that move first (Phys Ther, 1997; 77: 132-44).
Because the body's core is the master muscle group, a weak core can cause all manner of seemingly unrelated injury to the extremities. For instance, it was found that athletes with weak core control were more likely to develop foot/ankle injuries due to excessive movement of the hip when moving the legs (Arch Phys Med Rehabil, 1995; 76: 1138-43).
Other studies show that people predisposed to leg injuries are more likely to have weak hip abductors (the muscles that move the legs away from the midline) and weak hip rotation (Med Sci Sports Exerc, 2004; 36: 926-34). Also, among young female athletes, those with knee-joint pain were had significantly weaker hip abductors and hip rotators compared with controls (J Orthop Sports Phys Ther, 2003; 33: 671-6).
The chief hip external rotator muscle is gluteus maximus, the main muscle of the buttocks. As unlikely as it seems, weakness in this important muscle, and a lack of core strength in general, is related to ankle injuries (lnt J Sports Med, 1994; 15: 330-4).
Sometimes, injury to an extremity creates a vicious circle: the poor core stability makes a repeat injury more likely as well as other knock-on effects. Indeed, if core weakness is ignored, just one ankle injury can lead to a chronically bad back and poor motion control (lnt J Sports Med, 1994; 15: 330-4).
Back problems in general are due to core instability, especially weak or atrophied buttock muscles (lnt J Sports Med, 1994; 15: 330-4). Weak buttocks cannot hold the pelvis properly as you walk. This kind of core weakness can persist for years after the initial injury (Arch Phys Med Rehabil, 1995; 76: 1138-43).
The degree of core stability required may depend on gender, and women may need to work harder than men. In male and female athletes assessed for hip abduction and rotation strength, and strength and endurance of abdom-inal muscles, and of the back and lower spine, it was found that men had more strength and movement in the hip and lower back muscles. Also, it appears that the athletes who avoided injuries had strong hip abduction and rotation.
Further analyses showed that a restricted hip rotation capacity was the only reliable predictor of injury. The researchers concluded that gender-based postural differences could be behind the greater injuries sustained by athletic women (Med Sci Sports Exerc, 2004; 36: 926-34).
This is another reason, besides vanity, that active women should work on that six-pack.
Correcting core weakness
Core strength includes strong hip and buttock muscles, and strong and supple lower back muscles. You can achieve this with Pilates, certain yoga exercises (the Salute to the Sun, in particular) and a Swiss ball, which works the core muscles as you need to use them to maintain your balance.
However, you don't need a gym for a strong core. Simple floor exercises can work just as well.
- The plank: Holding yourself in a straight position, supported by your elbows and toes, tightly clench your abdominal muscles for up to one minute to strengthen them.
- The classic bridge (for gluteal muscles): Lie on the floor, then with your shoulders on the floor and knees bent, squeeze your buttocks together
as you push your hips up to make a straight line from your knees to your chest.
- Hip abduction: Lie on your side, making sure that your hips are 'stacked' (aligned); while holding your abdominal muscles tight, lift the top leg slowly up and down. Do several sets of at least 5-10 repetitions on each side.
- Hip rotation: Lying on your back with your arms out to the sides, lift your legs up to a 90-degree angle-soles to the ceiling-and, keeping both legs together, slowly swing them down to the floor, alternating sides. Then, keeping your lower back and trunk on the floor, bend your legs and allow the knees to fall to the floor on each side of your body.