Flaws of the musculoskeletal system

What are the flaws of the musculoskeletal system?


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I'm assuming you mean the typical endoskeletal system of animals and how muscles interplay with it? Perhaps its best to make a comparison to the exoskeletal system of insects. The external skeleton allows much better protection of the softer tissues and organs and affords much better leverage to be achieved. This allows insects to carry very heavy loads, much heavier than themselves, something we cannot do.

The exoskeleton does have some disadvantages such as the requirement for shedding to permit growth and the accompanying periods of vulnerability and I also think that there are limits that cap the ultimate size one can achieve with an exoskeletal system before the weight of tissues inside the structure cannot support itself. The endoskeletal system obviously isn't limited by this as much, thus animals using this strategy can attain much larger sizes.
Perhaps you mean the human musculoskeletal system?

We've got particularly bad lower backs, due to how we evolved to become bipedal. I can really be more specific than that, but it accounts for why so many suffer from lower back pain.

There's also the problem with women's hips. Infants have to have small brains and underformed skulls to fit through the birth canal, which is why they're so helpless when they're born. But the hip is wide enough that it's fragile, which is why broken hips due to falls is a problem with elderly women.
Cheers for the responses. Yes I meant the human musculoskeletal system. Maybe also the muscle is normally acting at a disadvantage? But the advantage of that is a small change in contractile force gives a large change in movement...
Can you put your question into some context? Because without this you can have a free for all: muscles cannot function without blood supply, there is an unbalanced number of opposable digits (1 against 4), the skull position is off-balance, we lack rotational joints, the rate of muscular growth can exceed tendon strenghtening, we only have two arms, all sorts of things that may or may not be considered flaws, depending on context and purpose.
The question is exactly the way I put it: maybe they want a general argument...
gamecube999 said:
maybe they want a general argument...
They? This is a school assignment? What subject?
No - it's a past uni question - anatomy...


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We've got particularly bad lower backs, due to how we evolved to become bipedal.
Just a ridiculous assumption. Our back is a perfect machine but our static life our misery.
This isn't a correct statement since pain in the lower back is attributed to the fact humans used to walk on all fours, but when they became bipedal the spinal column did not advance as much as it should have. If it had the lower portion of the spinal column would much thicker and stronger than it is right now.

TRCSF's statement is accurate.



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we are walking since 5 miliions years.
anymore? I cant think of many ideas


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I've always thought the MS system had a fundamental flaw - the inability to maintain a passive tone in fast skeletal muscle fibers.

For that to happen, the muscle has to remain contracted without the expenditure of significant amounts of energy. This actually happens consistenty post mortem and randomly in life with a rigor state configuration of the myosin on the actin. The myosin remains locked onto the actin and needs an ATP molecule (energy carrier) to detach and resume crossbridge cycling. If ATP is not forthcoming the myosin and actin remain in a locked state and the muscle remains at a fixed length. This is the explanation of rigor mortis, and the state remains until proteolysis dissolves away the bonds.

In life, myosin and actin never get into a perma-lock state like that. This is why when carrying a heavy load, or even pushing against a wall, the endless cycling of myosin and actin end up costing energy (ATP and glycogen) and causing the build-up of lactic acid, leading to fatigue and pain.

I find this more than a little inefficient. Cycling during the increasing phase of force generation is unavoidable, but I should be able to consciously lock my muscle into a pseudo-rigor state in order to maintain a contracted tone without energy expenditure or fatigue. This will, for example, help me to keep carrying a heavy dumbbell for hours on end - the relevant parts of my forearm and arm just become like a rigid mannequin.

There are dangers of course. Once the muscle is locked into a passive tonic state, a sudden increase in the load can tear the muscle apart physically. I doubt stretch reflexes are going to be fast enough to prevent that since ATP influx has to unlock all the acto-myosin crossbridges to get the muscle into active mode once more to allow correction. It will be too late to prevent muscle damage.

But I've often thought that were I to play God and build a perfect human, I would incorporate some mechanism to allow fast skeletal muscle to maintain a high state of tone for nil or negligible energy expenditure for hours on end. I don't think it's unfeasible.
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misskitty said:
This isn't a correct statement since pain in the lower back is attributed to the fact humans used to walk on all fours, but when they became bipedal the spinal column did not advance as much as it should have. If it had the lower portion of the spinal column would much thicker and stronger than it is right now.

Actually, you're both correct on this. Other than back pain caused by injuries while lifting improperly, a sedentary lifestyle is a risk factor for back pain. Weak muscles put people at higher risk of back injuries and/or pain.

Sedentary Lifestyle. People who do not exercise regularly face an increased risk for low back pain, especially during times when they suddenly embark on stressful unaccustomed activity, such as shoveling, digging, or moving heavy items. Although no definitive studies have been done to prove the relationship between lack of exercise and low back pain, sedentary living is probably a primary nonmedical culprit contributing to this condition. Lack of exercise leads to the following conditions that may threaten the back:

Muscle inflexibility (can restrict the back's ability to move, rotate, and bend).
Weak stomach muscles (can increase the strain on the back and can cause an abnormal tilt of the pelvis).
Weak back muscles (may increase the load on the spine and the risk for disc compression).
Obesity, associated with sedentary lifestyle (may put more weight on the spine and increase pressure on the vertebrae and discs). Studies report only a weak association between obesity and low back pain, however.

The most common type of back pain is lower back pain. That's because the lower portion of the back is under the most pressure when a person is sitting or lifting, and it can be easily damaged. Lower back pain is pain in the low lumbar, lumbosacral, or sacroiliac region, possibly accompanied by pain radiating down one or both buttocks or legs in the distribution of the sciatic nerve (sciatica). The lower back is an elegant construction of bone, muscle, and ligament. Because the lower back is the hinge between the upper and lower body, it is especially vulnerable to injury when you are lifting, reaching, or twisting. When low back pain strikes, we become acutely aware of just how much we rely on a flexible, strong back. Ironically, most of us don't think of the importance of keeping our back and stomach muscles strong until we have back trouble. The lower back supports most of the body’s weight, and as a result, is susceptible to pain caused by injury or other problems. Over 80% of adults experience low back pain (LBP) sometime during their life.1 More than half will have a repeat episode.

Is there relief for ongoing back problems?

Treatment of ongoing back problems must be directed at the cause. This may mean losing weight (because being overweight can make back pain worse), getting your muscles in better shape, and improving your posture when you're sitting, standing and sleeping.

Tips for preventing back strain

Don't lift by bending over. Lift an object by bending your hips and knees and then squatting to pick up the object. Keep your back straight and hold the object close to your body. Avoid twisting your body while lifting.
Push rather than pull when you must move heavy objects.
If you must sit at your desk or at the wheel of a car or truck for long hours, break up the time with stops to stretch.
Wear flat shoes or shoes with low heels (1 inch or lower).
Exercise regularly. An inactive lifestyle contributes to lower back pain.
http://familydoctor.org/117.xml [Broken]

Benefits of exercise for back pain
For many people, the key to a healthy back is proper exercise. You can minimise the problems related to back pain with exercises. These exercises make the muscles in your back, stomach, hips and thighs strong and flexible. Some exercises help to strengthen your back and stomach muscles, while other exercises are designed to improve your posture. A 30-minute aerobic conditioning program three times a week is ideal for overall fitness. Walking and/or water exercise are highly recommended for most people with back problems.

We've evolved fairly well to be bipedal, but we haven't evolved to sit or stand still for long periods of time. It's the strain of that inactivity that contributes to much of the back pain people experience. The adaptations to the spine that make it possible for us to stand erect also make us vulnerable to lower back pain and injuries given our current lifestyel.

[When you compare] a human vertebra, a chimpanzee vertebra, [and] the vertebra of a lemur, you can see that the human and the chimpanzee are much more similar to each other when compared to the lemur. That's because the human and the chimpanzee have adaptations for upright posture. The human and the chimp vertebrae are very short. They also have fewer vertebrae, which makes for a short spine, which is very stable in upright posture. In comparison, the lemur has elongated vertebrae and more vertebrae, which gives it a lot of flexibility and a wider range of motion for their quadrupedal movements.
Q: What are the differences between humans today and our closest living relatives, chimps, that allow us to be bipedal while they really aren't?

A: If you compare the human body to that of a chimpanzee, there are a lot of similarities in the upper body: the arms, the chest, the upper trunk. But there are many changes from the waist down, many differences between humans and chimpanzees that allow us to walk bipedally all the time. For example, in the lower back humans have a curve, a forward curve called lordosis, that you don't see in any other primate, which allows us to balance our upper body over our legs. The vertebrae themselves are much bigger in humans relative to body size than in any other primate, which allows us to bear the loads which are coming from the upper body through the lower back all day.

Evolution is also the origin of apparent anatomical anomalies such as the vulnerabilities of the lower back.

Note that they use the word "apparent." That this vulnerability exists doesn't mean it is an abnormality or flaw of any sort, it means our activities have changed from those which originally influenced the evolution of the structure of our backs.
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