Core strength is necessary for weight training to improve performance and prevent injuries. if your core is strong, then you will be strong and stable enough to lift weights and maintain your form without injury. Combining your core workout with your weight training will improve your results and save you time.
Your core includes your buttocks, pelvic floor, back, and all of the deep, small muscles that support your spine. When you move your body, your core stabilizes its position to prevent misalignment or overstretching. It also transfers force from your lower body to your upper body to produce strength, especially in weight training.
Core = body- (legs+ arms)
In brief, the muscles of the core do two main things: stabilize the torso, and dynamically move it in a rotational manner.
A strong core reduces back pain as is stabilizes the lower back. It improves flexibility, performance and balance as well as reducing the risk of injury.
But not all traditional training routines focus on the core. If you train regularly with weights in a gym, it is likely you have been focusing on movements and exercises which ignore the static and dynamic functions of the core. For example, consider bench press, deadlift and squat.
The bench press, although a great movement for packing on size and strength, does little to work the core as both sides of the body are balanced. There is no static resistance required by the obliques, and as the torso does not twist at all during this movement, there is zero dynamic core involvement.
In the same way, the deadlift, although involving the lower back, does not involve any rotational function of the core.
The traditional back squat is also a bi-lateral movement. The static and dynamic potential of the core is not challenged much at all.
So?!! How to build it?
There is a vast number of exercises that strengthen the core, many of which can be done at home with no equipments needed, just your own body weight. Here is an idea for your quick core workout: