This post from July 2010 was updated March 2020.
When we think of "good posture" we often think "shoulders back," but when we do "good posture" we're often not pulling our arms back as much as we are lifting the ribcage and pushing the pelvis forward. Our "stand up straight" tends to include a lot of pelvis forward. This can seem like a subtle difference, I know, but from a mechanical perspective, these positional changes can alter the angles at which you're loading your body—up to 30° in some places!—which means the way your body works is also altered.
How's my posture here? It's tough to say, if you're not sure where to look or how to evaluate. I'm definitely not slouching, but is this all that it takes?
When we use objective markers, physical loads are easier to understand. Below I've add a line through the ankle, knee, and hip joint, to see how this posture measures up, and I've also included a picture where I've backed my hips up to create a vertical leg.
If you're evaluating alignment, yours or others', you can hone your mechanical eye to look for the relationship between the ankle, knee, and hip joints. Then, extend a line through those points to see if there's a forward (non-vertical) lean to the lower body. To adjust, just shift your hips back until those three points stack directly over each other.
When the major axis of the body forms a plumb line, this neutral position can maximize structural support of your body weight as well as maximize your movement potential in all directions.
Back up for feel-good feet
Using that same mechanical eye, draw a vertical line from the hip joint to the floor. This helps show that where you wear your pelvis affects where you wear your weight on your feet. The forward pelvis in the left photo (above) places the burden on the front of the foot, where the smaller bones and muscles have to deal with it, and the backed up pelvis in the right photo places it on the much bulkier and dense rear foot—freeing up those smaller foot parts and fascia for better balance, movement, and healing they might need.
Backing up your hips is easy, fast, and free, but you might have already noticed that you can't do this while wearing a positive-heeled shoe. Shoes with any heel automatically force you to move the pelvis forward (and also bend the knee, depending on the height). So try backing up your hips while barefoot, bringing your weight far enough back to lift your toes off the ground. Now you have a sense of your weight being over your heels!
Back up for weight-bearing hips
I REALLY LOVE DRAWING LINES, FOLKS. When we think of weight we usually think of how much we weigh (which seems right, right?), but weight is really how much of your mass is being pulled on by gravity in a vertical direction.
In the picture on the left, my pelvis is not over my legs, which means the weight of the parts above my legs are not carried or felt by the bones of my legs. In this position gravity ends up "bowing" my body rather than compressing it. When I back my hips up as in the right photo, my weight is now moving downward through my leg and pelvic bones. My body mass is the same in both pictures, but because weight is a vertical force, the less vertical you are, the less you "weigh," from the standpoint of your legs, hips and pelvis.
Who wants weight-bearing hips? We do. When it comes to strong bones, we're in search of weight-bearing exercise and that's fine, but so much of the time we're not even carrying the load of our body in a weight-bearing fashion. First, we don't move that much at all. So sitting a lot takes the load off your hip joints, making them bear very little weight. Second, when we do move, our alignment is such that our hips aren't carrying much of it. Our culture has major issues with bone loss, but just think about it for a minute, how things came to be this way. Then, consider that your first stop on the osteogenic (bone-building) train can be carrying your body weight in a weight-bearing fashion. Get your hips over your ankles and your torso over your hips, and then walk around a lot.
Backing up and your lower back
Again, using the images just above, check out the movement of the lower back in a forward-hip position. Constant forward-motion of the pelvis relative to the backward-motion of the torso creates lumbar compression, which changes the angles and loads to the vertebrae, intervertebral discs, and sacrum. What can you do? YOU CAN BACK YOUR HIPS UP. Also, drop your ribs to decompress things from above.
Backing up for pregnancy and diastasis recti
For more on how alignment impacts pelvic health, read Our Best "Healthy Pelvis" Resources. You can read more about basic alignment adjustments and the exercises that make them easier in these titles (find the one that best suits your movement needs!): Move Your DNA, Diastasis Recti, Dynamic Aging.