Why do we humans have bones, and why do we humans need bones?
Why do we humans have bones, and why do we humans need bones? We have bones because we live in the weight-bearing environment of gravity. Gravity pulls against us all the time. The human skeletal system provides resistance to gravity
so we can move. Some creatures live in an environment where they don’t have this gravitational load, and their body is modeled to fit their unique needs. Sea Nettles don’t weigh much, they live in the water, and they essentially are carried along with the ocean currents. Yes, they have muscles, and they can use them to move through the water a little. There are no bones to which the muscles can attach and pull against. Their muscles simply swish water around, bringing food to them. Any motion they achieve is a bonus. So, although Sea Nettles can move, they don’t move very fast, and they can’t control their speed or direction. You’ll never see a Sea Nettle leap out of the water. They can’t, because Sea Nettles have no bones. No skeletal system was created or modeled for them, by them, because they don’t need one. But the bony structure of a whale offers enormous area for muscles to attach, so whales can control their speed and direction.
The skeleton of the whale has been designed and modeled so they can use their muscles and bones to push themselves through the great pressure of the deep. Their skeleton allows them to also jump right out of the sea. Motion like this requires a strong skeletal system. Which brings us to, us. This is why we have bones, and why we need bones.
The most obvious function of the human skeleton is to support the body against gravity, and to allow us to move. The bones have places where muscles attach. Muscles always attach between one bone and another. When the muscles are contracted, one of the bones moves in relation to the other. The brain and central nervous system coordinates all these functions.
Bone Protects the Nervous System
Where bones and muscles are concerned, coordinated by the brain and nerves, we can control our speed, direction, and hundreds of other specific functions. Doctors are concerned about ‘fragility fractures’, primarily of the neck of the femur where ‘the thigh-bone connects to the… hip bone.” The femur is a large bone, and normally a very strong bone. The strength of the femur comes from actually just using it in normal activities, as we’ll see. The less it is used, the less strong it becomes. Regarding the femur in ordinary daily activities, from Stanford University* “Large forces are supported by the bones of the lower limb during ordinary activities such as rising from a chair, walking, or climbing stairs. The magnitude of the forces at the hip joint frequently exceeds three times body weight.” Regarding the femur in active people, same article: “The bones of the lower limb must be capable of withstanding the repeated application of these loads as many as 10,000 times each day for an active individual.”
Poles are manufactured with ratings corresponding to the vaulter’s recommended maximum weight. Some organizations forbid vaulters to use poles rated below their weight as a safety precaution. Though such rules are rarely enforced, they know if the structure cannot carry the weight, it could break. This would be like a weak or fragile bone breaking because the load was too great, such as a fragility fracture of osteoporosis. The recommended weight corresponds to a flex rating that is determined by the manufacturer. They place a standardized amount of stress on the pole and measure how much the center of the pole is displaced. In other words, they bend it until it breaks, and then add a margin of safety to come up with the rating. In the pole-vaulting model of bone extremes, in this sequence of photos, we see the pole bend under the load, and return to a normal non-stressed condition.
This is how the trabecular structures of the bones are supposed to work:
The collagen matrix of the bone allows it to bend (not this much, of course) under the stress of daily activities, then returns to normal at rest.
Too much mineral
not enough collagen, and the bones will be too dense and brittle.
(Extreme example = osteopetrosis)
Too much collagen
not enough mineral, the bones will be too soft and flexible.
(Extreme example = osteomalacia, rickets)
Not enough mineral, and not enough collagen
= the bones will be delicate and brittle – no strength, no flexibility.
(Extreme example = osteoporosis with risk of fragility fracture.)
There is a simple analogy here, comparing the pole to normal bone function. The pole vault pictures demonstrate how low density, high quality structures with flexibility can resist fracture. Not that it can’t break, because it can… but it resists fracture well because of the other quality – not the density, but the flexibility. This is like the person who has a very, very low bone density T-Score – significant osteoporosis as measured only by density – and why they can go their whole life without a ‘fragility fracture’. Their bones are flexible and strong, even though they are not dense. Lastly for this page of bone extremes and models of bone and human skeleton system… The weight of the body (plus whatever we carry) is transferred from the hips through the femurs, then the knees, all the joints, eventually through the feet to the ground. The neck of the femur has an angle that creates a structural / functional challenge, unique from all the bones of the body. The design of the femur is a trade-off between weight-bearing and the ability to swing our legs in order to walk.
Bottom line – unique structure, unique function, unique risks of fracture.
Even though we have two legs to distribute the weight of the body equally, this really only happens when we are standing still. So really, with every step, each femur carries the entire weight of the body, one side at a time. And as we saw above from the Stanford University Research & Development paper, “The magnitude of the forces at the hip joint frequently exceeds three times body weight.” So we know with certainty that our skeleton system is innately ‘over-designed’ for routine daily activities. From studies at NASA as they try to restore bone density to the human skeleton after astronauts experience extreme bone-loss from lack of gravity, we know density and strength can increase at it responds to mechanical loads, such as lifting weights. And where there is no gravity, NASA is now using designing skeletal models to experiment with another mechanical force – vibration – to add a mechanical load to the body to maintain muscle mass, joint function,and bone density. In this model to study the human skeleton, vibration therapy is a gentle mechanical force that effectively stimulates bone growth, with or without gravity. I encourage you to go see the Caber Toss, and other events, yourself. The Scottish Highland Games are held at many sites around the country, and they are an impressive and unforgettable experience.
The Caber Toss
Remember, the femurs are designed to carry the weight of the entire body by itself, and to do so without breaking, while carrying heavy objects and running. And then some. The Caber is a wood pole 15-20 feet long, 9 inches thick at the big end, about 5 inches thick at the other. Total weight is about 150 pounds. (It can be as short as 15 feet, as long as 20.) In this event, the weight of the mans body, from the head to the hips, plus the 150-pound caber he just picked up from the ground, is transferred through the neck of the femur, through the legs and feet to the ground. Then, holding the caber, he begins to run with the pole, carrying it as nearly upright as he can, building momentum until he suddenly stops… planting his feet and heaving the caber into the air so that it goes end-over-end… with enough control of the throw so that the caber lands directly in front of him at the 12 o’clock position. And to top that, in the play-offs or the finals to determine the champion, finalists toss a caber 2 feet longer, and 50 pounds heavier.
I’m not suggesting for one second that anyone start tossing the caber. These are extreme examples of the body’s ability to build bone according to what we ask of it. With the highest degree of certainty, yes. How?
Water, good nutrition, and exercise, one day at a time, every day.
Lets go back to the caber toss for one more minute to see how tossing a caber relates to low bone density. Growing new bone requires using your bone – again, start easy, and do it over and over until you accomplish your goal. These boys didn’t just walk over to a telephone pole and pick it up. In fact, they first started with the pole-vault pole for practice – same length as the caber, much lighter. They needed to develop more than just bones and muscles; they required the coordination skills and balance before they could add the heavier weight of even a ‘beginners’ caber. And over time, with repeated mechanical loading (exercise and practice) their nerve system developed the balance and coordination required to hold and control the caber. And over time, the entire skeletal system and the joints and all their muscles grew and modeled and developed to the point where they were able to perform the task being asked of them – to control and then actually toss the caber.
I’m suggesting to anyone, that with time, with a little mechanical loading (exercise), that your bones (and muscles, joints, nerve system) can do the same thing. You can re-model your skeleton, joints, muscles, and nerves. You can increase their function, cooridination, density, strength, and flexibility such that osteoporosis – and the risk of fragility fracture – simply is not an issue. Remember, we don’t need to build extreme bones, we only need to maintain normal bones.
And included in this model is an increase in over-all health and wellness – a body that functions at its optimum and best. How can I be so confident of this? From my ongoing and extensive review of the literature, certainly. More importantly, we have learned this from our bone density consulting work with the women of Curves. Average, normal women, creating remarkable changes in density. Using safe, natural, effective methods.