For decades, this assumed relationship has been used to explain why women don't have wider hips, which would make childbirth easier and less dangerous. The argument, known as the "obstetrical dilemma," suggests that for millions of years female humans and their bipedal ancestors have faced an evolutionary trade-off in which selection for wider hips for childbirth has been countered by selection for narrower hips for efficient locomotion.
A new study, however, shows that what was widely assumed to be fact is, in actuality, almost entirely incorrect. A new study, conducted by researchers at Harvard in conjunction with colleagues at Boston University and Hunter College, found no connection between hip width and efficient locomotion, and suggests that scientists have long approached the problem in the wrong way.
First, the way we had modeled the forces involved didn't make sense. Second, we found that you can't predict, from the width of the pelvis, how much energy someone is using, so we've been looking at this biomechanical problem entirely wrong. The study grew out of research Warrener conducted as part of her Ph.
At the same time, Lieberman and Kristi Lewton, a former postdoctoral fellow in Lieberman's lab who is now at BU, were exploring the same problem. When the two teams discovered they'd been working on similar tracks, they decided to combine their efforts into a single study.
This is going to change the way we teach Anthropology everywhere, and it's going to change the way we teach about human evolution and walking adaptations and the birth of babies. I think it's a great example of how new things can be uncovered when you really bother to look deeply at accepted ideas. At the heart of why those earlier ideas were wrong, Warrener, Lieberman, Pontzer and Lewton discovered, were fundamental problems with the simple biomechanical models used to understand the forces acting on the hips.
And when you place your foot on the ground, forces don't just shoot straight up from the ground to your hip. By the time they arrive at your hip, they aren't acting on your body in this idealized way.
To understand what was really happening, the researchers turned to a biomechanical technique known as inverse dynamics. Rotational movements at all joints, including the hip, are the product of forces generated by muscles or gravity, and a key biomechanical variable known as a moment arm, or lever arm.
In the case of the pelvis, two moment arms are of special importance. One is the moment arm from the center of the hip joint to the body's center of gravity. The other is the moment arm from the center of the hip joint to the abductor muscles along the side of the hip. These critical muscles stabilize the hip when only one foot is on the ground.
Can a doctor really look at your body and determine if a baby's going to pass through? And it turns out, a trial of labor is the only way to determine whether those factors line up properly for a successful birth, Hart tells Romper. The good news, however, is that it's extremely rare for it not to. There are, however, more optimal shapes to the pelvis that allow babies to change position and move easily out of the birth canal.
A gynecoid pelvis is the ideal shape for childbirth, Hart says, because of its bowl-like appearance from above and round inlet that allows infants to escape the pelvis with little interference from their mother's bone structure. Other shapes include android, anthropoid, and platypelloid that either have more narrow inlet openings or less room front-to-back for the baby to get into position.
But what does it look like when pelvis shape does come into play? Labor would stall out and a C-section would become necessary. Nipples typically lighten a bit, but will often remain permanently a few shades different than they were before pregnancy. Hips widen during pregnancy in anticipation of pushing a baby through the birth canal. The hormone Relaxin is released by the body to help relax pelvic joints and ligaments. The area most impacted by this is the pelvis, the changes of the pelvic bone structure is what makes women comment on their wider hips.
For those who have always wanted more of an hour glass figure, they may be jumping for joy over their new curves, for those who already rock the wide hips, this may be a source of stress.
Just know that your hips have done wonderful things and birthed your beautiful baby! Most new mums probably notice their aching backs more than they notice poor posture, but this is a long-term post-pregnancy ailment just about everyone experiences. The whole experience of being with child, breastfeeding, and carrying a baby in the arms will put a lot of focus on the front of the body.
This means other areas, like the back and shoulders, may curve. This curvature can lead to poor posture and backaches. Some of this can be combatted by ensuring proper back support during breastfeeding even a couple of pillows will do this. A good way to help your posture after having a baby is using baby carriers or wraps to keep little ones close in a way that benefits your posture. Izmi Essential wrap is great for newborns as a wrap it is ergonomic and supportive.
Its made to provide comfortable closeness with simple, flexible, and adaptable support where weight can be distributed evenly, therefore, reducing the pressure on your back. New parents may joke that their children have given them grey hair, but they really might have!
There is some debate among both hairdressers and doctors as to whether this change has to do with hormones, stress from parenting, additional hair falling out in the months following birth or simply because a new mum has significantly less time to head to the hairdresser and tend to her hair!
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