poor posture is a clear indication of having a weak core. The muscles that make up your abdomen and lower back help in stabilizing the pelvis spine that in return helps keep your upper back and shoulders in a neutral position. Lack of strength in these muscles causes you to have slouchy posture.
Another indication of weak core is pain in lower back. When you’re core is not strong or balanced as it should be, the curvature of your lumbar spine is likely to change. Even the slightest pressure on the vertebrae makes your spine as well the muscles more prone to injury.
Weakness in arms and legs can also indicate that your core muscles are weak. If you find it difficult to throw a ball or landing a punch, it means that your core strength is not strong.
Another potential indication of weak core muscles is the inability to hollow your stomach. Take a deep breath and as you exhale, try to pull your belly button in toward your spine. Hold it for few seconds or till the count of 10 and then, release. If can’t sustain the hold for the entire count, this means that your core is weak.