First thing's first:
Bad posture does not necessarily imply back pain. Some people are naturally born with protracted, rounded shoulders, hyperlordosis, or hyperkyphosis (excessive curvatures) of the spine. When this happens, the body makes adjustments to accommodate the forces that act on it during daily activities, such as sitting, standing, and lying down.
Next question:
Without any physical limitations or deficiencies, however, bad posture being correlated with back pain brings a question similar to that of "what came first - the chicken or the egg?" You must decide which scenario better fits your situation.
Back pain can cause a negative shift in posture to accommodate and relieve the pain - back pain comes first.
OR
Poor posture, including slouching, rounded shoulders, head and neck, cause increased stress on the muscles of the back, causing pain.
Thirdly:
Bad posture, without any anatomical limiting factors, is typically caused tightness of certain muscles, mixed with weakness of others. In addition to muscular deficiencies, there are likely going to be some joints that are misaligned within the spine.
Let's start with the muscles.
A mixture between hip flexor tightness and pectoral tightness, along with scapular weakness and core weakness are 8/10 musculoskeletal cause of poor posture.
Tightness in these areas are more likely to come from more stagnant lifestyles; which doesn't necessarily mean sedentary, more along the lines of many activities may cause similar positions.
For example: a business man who works a desk job is also an avid cyclist. Sitting in a desk chair all day, then cycling many miles in a hunched position, then come home to eat dinner seated, unwind seated, would mean their lifestyle is positionally stagnant.
In other words, you may be an active person living an decently active lifestyle, but if you sit and think about it, many of the activities you partake in involve the same anatomical positions. Keep in mind, some are more prone to problems related to this than others.
Misaligned Joints:
Almost every single muscle of the body inserts onto a bone. Keep in mind, your skeleton is simply a lever system controlled by the muscles. Your bones don't move, your muscles pull on your bones to make them move.
So with that in mind, picture a person with half of their muscles tight, and half of their muscles weak. All of those tight muscles are pulling hard on their bony insertion points, and when their muscular counterparts are too weak to keep the bones in place, the joints will become misaligned. This can cause over-stretching of the weaker muscles, and nerves to get pinched underneath the tighter muscles.
Ergo, how bad posture can lead to back pain.
Lastly:
How do you naturally combat this?
1. Ensure good joint alignment.
When you bend down to put a dish away, make sure you lower your body with your legs, and activate those glutes. They're relatively speaking to strength, some of the most influential muscles in your body. Keep your knees over your ankles, and shoulders over your knees when squatting down.
2. Ensure good core activation.
Make sure when lowering your own body down into a squat, picking/lifting any objects, and even sitting and standing, that you are keeping your core tight. Not sure what this means? Lay down on your back, look down at your belly button. Next, find your hip bones - these mark the start of the front of your thighs. Place two fingers just on the inside of each of those hip bones and say "SSS" short and quick. Feel that contraction? That's your core. Keep it contracted. The stronger it is, the less back pain you'll have.
3. Work on your movement.
Be very aware of the movements you perform on a daily basis that cause pain or discomfort. Your physical therapist will want to know, and they'll give you exercises to relieve the tension on some muscles, and to strengthen others.
4. Vary your posture.
Mix it up! Sit at a desk 8 hours per day? Stand every couple. It's best for brain function to take a 5 minute break every hour, and it's best for musculoskeletal function to change positions every 20 minutes or so. This does not mean sitting to standing, maybe just sitting back in your chair to sitting forward with your hands or elbows on your desk. Most people slouch in their chairs without even noticing, so make sure to adjust your position frequently if you plan to stay seated throughout most of your day. Another option that helps from slouching is avoiding using the backrest of the chair.
Questions? Call or set up an appointment with our wonderful staff - we're all specialized in problems such as this!