The core muscle, are the muscle that stabilize your posture. It include the abdominals muscles, the back muscle, and the pelvis muscle (butt). It is important to keep them very strong, because weak core muscle, will cause, an imbalance when you move, wich will eventually cause, low back, pelvis, knee or hip problem. We have to do specific exercise in order to reenforce them.
Walking is a good general exercise for core strenghtening. But what I usually recommend to strenghtened those muscles is the stability ball, also known as the exercise ball or the swiss ball. One easy exercise you can do, is to just sit on it, watch tv, work, while sitting on it. Start with 15-30 min. and increase your time as you feel more confortable on the ball. Just sitting on the ball require you to keep your balance, and eventough you may not feel it, your muscle are working. There is many other exercises you can do on the ball. The next 2 videos shows you more exercise. There is also many books on the subject. The 4 point exercise, is a very good exercise to perform ( the first video ). Just remember to start slowly, and to contract the transverse, which are the abdominal muscle located at the pelvis, and don't forget to breath.
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