Because every human body is different and varies in shape, size and type, as well as muscularity, flexibility and fat-deposition patterns, it is not surprising that few people actually exhibit an “ideal” posture. There are various types of deviations from neutral spine position, which may be either temporary or permanent, and that can sometimes be improved through exercise alone.
Once you can activate your core muscles, and you can find your neutral spine, it’s time to challenge it more. Bridging is a harder exercise which will work through the back of the pelvis, hips and thighs.
There are multiple variations to try. Here’s an example.