Biomechanics is fascinating, and of course I think so but I’m not the only one, I promise. It’s weekly that I get an email from someone telling me that they wished they would have studied this field instead of…whatever, law or hairdressing — you name it. And, who wouldn’t love it? Biomechanics, when talking about a true, well-developed curriculum, explains so much about our physical experience that no other science can touch.
The first “biomechanist” — that is a person who had both the math and mechanics skills coupled with the biology/physiology know-how could be either Leonardo da Vinci or Galileo Galilei. Within a hundred years of each other, both of these dudes were working on trying to understand the functions of the human body with respect to the emerging laws of modern science — conservation of mass, leverage, etc. Leo was a levers and muscles guy, as you can probably tell from his drawings.
Galileo was more a “materials” guy — he was really interested in bones as columns, and how they needed enough mass to support the weight of the body in various situations but needed to be light enough to allow the human to be extremely mobile.
One of the reasons da Vinci and Galileo didn’t make more progress in this field (other than the fact that they were both Italian and probably drank a lot of wine) is that they only had basic mechanical laws that could be applied to rigid-bodies (discrete mechanics) and didn’t have a model for soft tissues that could change in response to a situation (continuum mechanics). For an easy example of this, picture a bone, like the one in your upper arm.
While this bone seems pretty stiff, it actually varies quite a bit in density as well as the type of bone cell depending on where you look and is not all that “solid”. It’s actually kind of porous too, especially when you look at it up close. When you apply a load to a tissue like this, some of that load ends up kind of bending the bone, although not so much that it breaks. Soft tissues handle loads differently than, say, a metal bar, because you have to convert some of the load to “bending” in this case. And different loads from where your body mass is relative to each bone and loads created by muscular pulls all create a different type of bend. The math gets a bit more tricky when you have to calculate not only the movement of the bone relative to the body but the movement of the bone relative to itself. Back in “the day”, when the emerging science laws were all about machines and mechanics and rigid bodies (like planets), there wasn’t any way to really talk about soft tissues with any mathematical authority.
Another example: When smart guys were first researching the cardiovascular system in the 1800s, the question was — are arteries “perfect elastic bodies?”
So, are arteries perfect elastic bodies? I hope so, because that would make it so easy to calculate how much blood is where and troubleshoot a clogged artery, etc. But, alas, it turns out that no, they’re not. Because there is smooth muscle that can change the size of an artery *snap* like that — and only in a tiny area. Which is great for the arteries (hooray for intelligent tissue!), but not so great for the scientists who need to publish something concrete about the amounts/values/data that can be applied to mass populations. When you add more recent findings that the muscular environment around the smooth muscle-walled artery affects what the smooth muscle (and therefore the artery) can do, you’ve really got a doozy of a problem. The “How Arteries Work” section of your physiology book doesn’t get to this level of mechanism. Partly because it’s based on information that’s 30-60 years old and partly because it has already been decided (by those that decide such things) that a pre-requisite for physiology should not include calculus-based physics. So, everyone gets the 10th grade version of the artery. In college.
FYI, I believe Perfect Elastic Bodies was the main article in last week’s People Magazine, but I could be wrong.
Where are we today, in terms of understanding how the human body works? Work initiated by the Leos, more than 500 years ago, still shapes much of the work being done in modern biomechanics courses as the progress of biomechanical science really fell off due just after the 1600s due to two things: the organization of curriculum, and chemistry.
As you can see, knowing “just” the mechanical laws doesn’t really help out much when it comes to really understanding biomechanical problems. You have to have a pretty well-developed cache (read: years of study) of biological background. In the 17th century, it was deemed that learning the anatomical system (that is memorizing the name of parts and their connection points) would be the best place to start for students. Of course, the human body is so expansive that by the time those experts in anatomy took an entire education on the names/shapes/locations, there was no time to give to equal learning of the mechanics — those are the laws that dictate how the tissue actually “works.” Fast forward to 2012, this way of teaching human science is still the standard across the board. A ton of people who know what it all is — without really much understanding the why or how it all works.
The second halt to biomechanics as a progressive theory was the use of chemistry to explain physiological phenomenon. Because (mathematically) evaluating and describing a moving body human tissue by tissue was too complicated, it became easier to reduce physiology to chemistry — as the chemical signals that follow a mechanoreceptor stimulation are pretty straightforward. A good example of this is (again!) bone.
Until the last 30 years, bone has been presented as the mineral reservoir to the body, a place to store minerals “until the body needed it.” Most of the theories about bone disease, mineral balance in the blood and nutrition are still based on this misunderstanding through oversimplification. It turns out that the body needs the bones more than what’s in them.
When data supporting the notion that bone was a tissue responding to mechanical signals (not chemical ones) with a primary agenda of maintaining itself was first presented in the 1960s, orthopaedic surgeon Harold Frost was regularly mocked or disregarded. Because he was presenting nonsensical or unsupported or unscientific stuff? Nope. Because he was presenting information people did not have a skill-set to understand.
And, when you don’t understand something (especially when you don’t have the skill-set to) it’s best to publicly announce why you don’t “believe” it. This is how it’s been done for centuries. Only now it’s done on Facebook, which should make for some interesting public record.
So where have all the biomechanists gone? Probably to the same place that we all go (to the bar?) when we realize that to truly learn something takes a lifetime and can’t be done only through books or only through intuition, but through a life-long pursuit of experimentation both formal and informal.
I do wish they’d return because what is extremely clear is that very few people have the skill set to comprehend how one type of movement or set of joint positions is mathematically unique when it comes to stimulating the body’s many tissues. Common knowledge (and practice) has been lost regarding the required frequencies, intensities, joint ranges of motion, and loads to every level of tissue in the body for the purpose of triggering the mechanoreceptors that stimulate tissue development. The term biomechanics should not be associated with exercise or fitness or performance. Biomechanics has to do with biological function. You don’t stimulate the mechanoreceptor, you don’t get the cell to work. Period.
I wonder how small one must be to qualify as a quantum mechanic? Sorry, physics joke.