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152-415: The DXA scan is typically used to diagnose and follow osteoporosis , as contrasted to the nuclear bone scan , which is sensitive to certain metabolic diseases of bones in which bones are attempting to heal from infections, fractures, or tumors. It is also sometimes used to assess body composition . Soft tissue and bone have different attenuation coefficients to X-rays. A single X-ray beam passing through

304-402: A displacement R AB , Newton's law of gravitation states that each object exerts a gravitational force on the other, of magnitude where G is the universal gravitational constant . The above statement may be reformulated in the following way: if g is the magnitude at a given location in a gravitational field, then the gravitational force on an object with gravitational mass M is This

456-460: A gluten-free diet decreases the risk of developing osteoporosis and increases bone density. The diet must ensure optimal calcium intake (of at least one gram daily) and measuring vitamin D levels is recommended, and to take specific supplements if necessary. Osteoporosis can affect nearly 1 in 3 women and the bone loss is the most rapid within the first 2-3 years after menopause. This can be prevented by menopause hormone therapy or MHT, which

608-405: A gravitational field . If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B , each body is subject to an attractive force F g = Gm A m B / r , where G = 6.67 × 10  N⋅kg ⋅m is the "universal gravitational constant ". This is sometimes referred to as gravitational mass. Repeated experiments since

760-411: A measure of the body's inertia , meaning the resistance to acceleration (change of velocity ) when a net force is applied. The object's mass also determines the strength of its gravitational attraction to other bodies. The SI base unit of mass is the kilogram (kg). In physics , mass is not the same as weight , even though mass is often determined by measuring the object's weight using

912-428: A ratio of the bone mineral content versus a cuboidal estimation of the volume of bone. Like the results for aBMD, BMAD results do not accurately represent true bone mineral density, since they use approximations of the bone's volume. BMAD is used primarily for research purposes and is not yet used in clinical settings. Other imaging technologies such as quantitative computed tomography (QCT) are capable of measuring

1064-529: A spring scale , rather than balance scale comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity, but it would still have the same mass. This is because weight is a force, while mass is the property that (along with gravity) determines the strength of this force. In the Standard Model of physics, the mass of elementary particles

1216-543: A 2.27 decrease in TUG times in their experimental group. The overall thing to note when prescribing exercise for individuals with osteoporosis is to evaluate the individual's needs and then individualize their program with multiple exercise modalities that work for them, emphasizing increasing muscle strength as well as maintaining bone mass. People with osteoporosis are at higher risk of falls due to poor postural control, muscle weakness, and overall deconditioning. Postural control

1368-432: A 70‑year‑old. A number of tools exist to help determine who is reasonable to test. Lifestyle prevention of osteoporosis is in many aspects the inverse of the potentially modifiable risk factors. As tobacco smoking and high alcohol intake have been linked with osteoporosis, smoking cessation and moderation of alcohol intake are commonly recommended as ways to help prevent it. In people with coeliac disease adherence to

1520-449: A benefit of vitamin D supplements combined with calcium for prevention of fractures, they did not find a benefit of vitamin D supplements (800 IU/day or less) alone. Regarding adverse effects, supplementation does not appear to affect overall risk of death, although calcium supplementation could potentially be associated with some increased risk of myocardial infarctions , stroke , kidney stones , and gastrointestinal symptoms. There

1672-432: A bone; they are therefore regarded as fragility fractures . Typical fragility fractures occur in the vertebral column , rib , hip and wrist . Examples of situations where people would not normally break a bone include a fall from standing height, normal day-to-day activities such as lifting, bending, or coughing. Fractures are a common complication of osteoporosis and can result in disability. Acute and chronic pain in

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1824-406: A bronze ball and a wooden ramp. The wooden ramp was "12 cubits long, half a cubit wide and three finger-breadths thick" with a straight, smooth, polished groove . The groove was lined with " parchment , also smooth and polished as possible". And into this groove was placed "a hard, smooth and very round bronze ball". The ramp was inclined at various angles to slow the acceleration enough so that

1976-462: A clinical FRAX is advised at age 50. Osteoporosis occurs when reduction in bone mass surpasses a critical threshold with greater susceptibility to fracturing. Fractures occur when the force acting on a bone is greater than the strength of the bone. To understand the pathology of osteoporosis and skeletal degradation, studying the mechanical properties and behavior of bone is crucial, due to the under-diagnosing of osteoporosis. Mechanical properties of

2128-534: A curved path. "For a stone projected is by the pressure of its own weight forced out of the rectilinear path, which by the projection alone it should have pursued, and made to describe a curve line in the air; and through that crooked way is at last brought down to the ground. And the greater the velocity is with which it is projected, the farther it goes before it falls to the Earth." Newton further reasons that if an object were "projected in an horizontal direction from

2280-465: A decreased ability to carry out normal activities. Osteoporosis may be due to lower-than-normal maximum bone mass and greater-than-normal bone loss. Bone loss increases after the menopause due to lower levels of estrogen , and after " andropause " due to lower levels of testosterone . Osteoporosis may also occur due to a number of diseases or treatments, including alcoholism , anorexia , hyperthyroidism , kidney disease , and surgical removal of

2432-601: A different policy as to what certifications are needed to operate a DXA machine. California , for example, requires coursework and a state-run test, whereas Maryland has no requirements for DXA technicians. Many states require a training course and certificate from the International Society of Clinical Densitometry (ISCD). In Australia, regulation differs according to the applicable state or territory. For example, in Victoria, an individual performing DXA scans

2584-513: A force from a scale or the surface of a planetary body such as the Earth or the Moon . This force keeps the object from going into free fall. Weight is the opposing force in such circumstances and is thus determined by the acceleration of free fall. On the surface of the Earth, for example, an object with a mass of 50 kilograms weighs 491 newtons, which means that 491 newtons is being applied to keep

2736-399: A friend, Edmond Halley , that he had solved the problem of gravitational orbits, but had misplaced the solution in his office. After being encouraged by Halley, Newton decided to develop his ideas about gravity and publish all of his findings. In November 1684, Isaac Newton sent a document to Edmund Halley, now lost but presumed to have been titled De motu corporum in gyrum (Latin for "On

2888-421: A gravitational field. Newton further assumed that the strength of each object's gravitational field would decrease according to the square of the distance to that object. If a large collection of small objects were formed into a giant spherical body such as the Earth or Sun, Newton calculated the collection would create a gravitational field proportional to the total mass of the body, and inversely proportional to

3040-406: A hammer and a feather are dropped from the same height through the air on Earth, the feather will take much longer to reach the ground; the feather is not really in free -fall because the force of air resistance upwards against the feather is comparable to the downward force of gravity. On the other hand, if the experiment is performed in a vacuum , in which there is no air resistance, the hammer and

3192-442: A low (for example 70 kV) and high (for example 140 kV) value in synchronism with the frequency of the electrical mains, resulting in effective energies alternating between 45 and 100 keV. The combination of dual X-ray absorptiometry and laser uses the laser to measure the thickness of the region scanned, allowing for varying proportions of lean soft tissue and adipose tissue within the soft tissue to be controlled for and improving

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3344-422: A material depend on the geometry and inherent structure of the materials. Bone as a material is very complex because of its hierarchal structure in which characteristics vary across length scales. At the basic scale, bone is composed of an organic matrix of collagen type-I. Collagen type-I molecules form a composite material with hydroxyapatite to make up collagen fibrils. The hierarchal structure continuous with

3496-949: A modification adapted to routinely collected health data. The term "established osteoporosis" is used when a broken bone due to osteoporosis has occurred. Osteoporosis is a part of frailty syndrome . There is an increased risk of falls associated with aging. These falls can lead to skeletal damage at the wrist, spine, hip, knee, foot, and ankle. Part of the fall risk is because of impaired eyesight due to many causes, (e.g. glaucoma , macular degeneration ), balance disorder , movement disorders (e.g. Parkinson's disease ), dementia , and sarcopenia (age-related loss of skeletal muscle ). Collapse (transient loss of postural tone with or without loss of consciousness). Causes of syncope are manifold, but may include cardiac arrhythmias (irregular heart beat), vasovagal syncope , orthostatic hypotension (abnormal drop in blood pressure on standing up), and seizures . Removal of obstacles and loose carpets in

3648-509: A need for supervision and precautionary measures. Studies of the benefits of supplementation with calcium and vitamin D are conflicting, possibly because most studies did not have people with low dietary intakes. A 2018 review by the USPSTF found low-quality evidence that the routine use of calcium and vitamin D supplements (or both supplements together) did not reduce the risk of having an osteoporotic fracture in male and female adults living in

3800-493: A negative effect on bone density). Risk of adverse events from the types of exercise usually considered appropriate for people with osteoporosis is generally low (though repeated forceful forward spinal bends are discouraged). For people who have had vertebral fractures, there is moderate-quality evidence that exercise is likely to improve physical performance, as well as some low-quality evidence suggesting that exercise may reduce pain and improve quality of life. Osteoporosis

3952-404: A scan is done outside one of these centers, it should not be interpreted without consultation with an expert in the field. Furthermore, most of the pharmaceuticals given to adults with low bone mass can be given to children only in strictly monitored clinical trials. Whole-body calcium measured by DXA has been validated in adults using in-vivo neutron activation of total body calcium but this

4104-634: A separate radiation dose, is sensitive to change over time, can analyze a region of any size or shape, excludes irrelevant tissue such as fat, muscle, and air, and does not require knowledge of the patient's subpopulation in order to create a clinical score (e.g. the Z-score of all females of a certain age). Among QCT's disadvantages: it requires a high radiation dose compared to DXA, CT scanners are large and expensive, and because its practice has been less standardized than BMD, its results are more operator-dependent. Peripheral QCT has been introduced to improve upon

4256-450: A spinal fracture index that takes into account the number of vertebrae involved. Involvement of multiple vertebral bodies leads to kyphosis of the thoracic spine, leading to what is known as dowager's hump . Dual-energy X-ray absorptiometry (DEXA scan) is considered the gold standard for the diagnosis of osteoporosis. Osteoporosis is diagnosed when the bone mineral density is less than or equal to 2.5 standard deviations below that of

4408-434: A stooped posture, loss of height, and chronic pain with resultant reduction in mobility. Fractures of the long bones acutely impair mobility and may require surgery . Hip fracture , in particular, usually requires prompt surgery, as serious risks are associated with it, such as deep vein thrombosis and pulmonary embolism . There is also an increased risk of mortality associated with osteoporosis-related hip fracture, with

4560-468: A string, does the combined system fall faster because it is now more massive, or does the lighter body in its slower fall hold back the heavier body? The only convincing resolution to this question is that all bodies must fall at the same rate. A later experiment was described in Galileo's Two New Sciences published in 1638. One of Galileo's fictional characters, Salviati, describes an experiment using

4712-410: A uniform acceleration and a uniform gravitational field. Thus, the theory postulates that the force acting on a massive object caused by a gravitational field is a result of the object's tendency to move in a straight line (in other words its inertia) and should therefore be a function of its inertial mass and the strength of the gravitational field. In theoretical physics , a mass generation mechanism

Dual-energy X-ray absorptiometry - Misplaced Pages Continue

4864-460: A vacuum, as David Scott did on the surface of the Moon during Apollo 15 . A stronger version of the equivalence principle, known as the Einstein equivalence principle or the strong equivalence principle , lies at the heart of the general theory of relativity . Einstein's equivalence principle states that within sufficiently small regions of spacetime, it is impossible to distinguish between

5016-642: A week, moderate to high intensity, activities should be multidirectional, and load should be more than typical everyday load on bones. Some examples of exercises are jumping, skipping, hopping, depth jumps, etc.  Recommended dosage for progressive resistance training is 2 or more days a week, intensity (load) should start low and increase gradually. Resistance training should focus on major muscle groups used for functional movements as well as muscles that have direct stress on bones susceptible to fracture. Considerations for resistance training are to teach proper lifting techniques and be careful with lifting weights above

5168-446: A young (30–40-year-old ), healthy adult women reference population. This is translated as a T-score . But because bone density decreases with age, more people become osteoporotic with increasing age. The World Health Organization has established the following diagnostic guidelines: The International Society for Clinical Densitometry takes the position that a diagnosis of osteoporosis in men under 50 years of age should not be made on

5320-485: Is a balance scale , which balances the force of one object's weight against the force of another object's weight. The two sides of a balance scale are close enough that the objects experience similar gravitational fields. Hence, if they have similar masses then their weights will also be similar. This allows the scale, by comparing weights, to also compare masses. Consequently, historical weight standards were often defined in terms of amounts. The Romans, for example, used

5472-450: Is a theory which attempts to explain the origin of mass from the most fundamental laws of physics . To date, a number of different models have been proposed which advocate different views of the origin of mass. The problem is complicated by the fact that the notion of mass is strongly related to the gravitational interaction but a theory of the latter has not been yet reconciled with the currently popular model of particle physics , known as

5624-399: Is a very prevalent disease in the elderly population but not much is known about the optimal prescription and dosage of physical exercise to help prevent bone mineral loss. A lot of the focus around osteoporosis is also prevention and not so much maintenance which should be the front runner when considering what approach to take. When prescribing exercise, an aspect to take into consideration is

5776-419: Is adequate for most of classical mechanics, and sometimes remains in use in basic education, if the priority is to teach the difference between mass from weight.) This traditional "amount of matter" belief was contradicted by the fact that different atoms (and, later, different elementary particles) can have different masses, and was further contradicted by Einstein's theory of relativity (1905), which showed that

5928-422: Is an imbalance between bone resorption and bone formation . In normal bone, matrix remodeling of bone is constant; up to 10% of all bone mass may be undergoing remodeling at any point in time. The process takes place in bone multicellular units (BMUs) as first described by Frost & Thomas in 1963. Osteoclasts are assisted by transcription factor PU.1 to degrade the bone matrix, while osteoblasts rebuild

6080-405: Is an obvious cost but it can be justified by the advantage of bipedalism inferring that this vulnerability is the byproduct of such. It has been suggested that porous bones help to absorb the increased stress that we have on two surfaces compared to our primate counterparts who have four surfaces to disperse the force. In addition, the porosity allows for more flexibility and a lighter skeleton that

6232-561: Is believed to be a result of their coupling with the Higgs boson in what is known as the Brout–Englert–Higgs mechanism . There are several distinct phenomena that can be used to measure mass. Although some theorists have speculated that some of these phenomena could be independent of each other, current experiments have found no difference in results regardless of how it is measured: The mass of an object determines its acceleration in

Dual-energy X-ray absorptiometry - Misplaced Pages Continue

6384-443: Is due to the missing depth value in the calculation of bone mineral density. Despite DXA technology's problems with estimating volume, it is still a fairly accurate measure of bone mineral content. Methods to correct for this shortcoming include the calculation of a volume that is approximated from the projected area measure by DXA. DXA BMD results adjusted in this manner are referred to as the bone mineral apparent density (BMAD) and are

6536-427: Is easier to support. One other consideration may be that diets today have much lower amounts of calcium than the diets of other primates or the tetrapedal ancestors to humans which may lead to higher likelihood to show signs of osteoporosis. In the absence of risk factors other than sex and age a BMD measurement using dual-energy X-ray absorptiometry (DXA) is recommended for women at age 65. For women with risk factors

6688-403: Is emerging with regard to other drugs. Osteoporosis due to pregnancy and lactation is a rare condition of unknown cause. Age-related bone loss is common among humans due to exhibiting less dense bones than other primate species. Because of the more porous bones of humans, frequency of severe osteoporosis and osteoporosis related fractures is higher. The human vulnerability to osteoporosis

6840-440: Is essential because the structure will translate to the mechanical behavior of bones. Previous work indicates that osteoporotic bones undergo specific structural changes that contribute to altered mechanical behavior. For instance, a study demonstrated that osteoporotic bone exhibits reduced bone volume fraction, trabecular thickness, and connectivity. In another study, osteoporosis in human cancellous bone led to 3-27% variability in

6992-653: Is important to maintaining functional movements such as walking and standing. Physical therapy may be an effective way to address postural weakness that may result from vertebral fractures, which are common in people with osteoporosis. Physical therapy treatment plans for people with vertebral fractures include balance training, postural correction, trunk and lower extremity muscle strengthening exercises, and moderate-intensity aerobic physical activity. The goal of these interventions are to regain normal spine curvatures, increase spine stability, and improve functional performance. Physical therapy interventions were also designed to slow

7144-479: Is insufficient evidence to make recommendations about the intervals for repeated screening and the appropriate age to stop screening. In men the harm versus benefit of screening for osteoporosis is unknown. Prescrire states that the need to test for osteoporosis in those who have not had a previous bone fracture is unclear. The International Society for Clinical Densitometry suggest BMD testing for men 70 or older, or those who are indicated for risk equal to that of

7296-411: Is just a comparison of what a patient's bone mineral density is in comparison to the average bone mineral density of a male or female of their age and weight. The WHO committee did not have enough data to create definitions for men or other ethnic groups. Special considerations are involved in the use of DXA to assess bone mass in children. Specifically, comparing the bone mineral density of children to

7448-529: Is lower than that normally needed to stimulate the uterus and breast gland . The α-form of the estrogen receptor appears to be the most important in regulating bone turnover. In addition to estrogen, calcium metabolism plays a significant role in bone turnover, and deficiency of calcium and vitamin D leads to impaired bone deposition; in addition, the parathyroid glands react to low calcium levels by secreting parathyroid hormone (parathormone, PTH), which increases bone resorption to ensure sufficient calcium in

7600-418: Is meant to prevent bone loss and the degradation of the bone microarchitecture and is noted to reduce the risk of fractures in bones by 20-30%. However, MHT has been linked to safety concerns, so it is not generally recommended. As far as management goes with this potentially limiting disease, there are practices that can and should be implemented within the daily lifestyle. For example, it would be beneficial if

7752-449: Is no evidence that supplementation before menopause can enhance bone mineral density. Vitamin K deficiency is also a risk factor for osteoporotic fractures. The gene gamma-glutamyl carboxylase (GGCX) is dependent on vitamin K. Functional polymorphisms in the gene could attribute to variation in bone metabolism and BMD. Vitamin K2 is also used as a means of treatment for osteoporosis and

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7904-476: Is not suitable for paediatric subjects and studies have been carried out on paediatric-sized animals. DXA scans can also be used to measure total body composition and fat content with a high degree of accuracy comparable to hydrostatic weighing with a few important caveats. From the DXA scans, a low resolution "fat shadow" image can also be generated, which gives an overall impression of fat distribution throughout

8056-682: Is relatively insensitive to detection of early disease and requires a substantial amount of bone loss (about 30%) to be apparent on X-ray images. The main radiographic features of generalized osteoporosis are cortical thinning and increased radiolucency. Frequent complications of osteoporosis are vertebral fractures for which spinal radiography can help considerably in diagnosis and follow-up. Vertebral height measurements can objectively be made using plain-film X-rays by using several methods such as height loss together with area reduction, particularly when looking at vertical deformity in T4-L4, or by determining

8208-542: Is replaced more often than cortical bone, providing early evidence of metabolic change. Also, the calcaneus is fairly flat and parallel, reducing repositioning errors. The method can be applied to children, neonates, and preterm infants, just as well as to adults. Some ultrasound devices can be used on the tibia . The U.S. Preventive Services Task Force (USPSTF) recommend that all women 65 years of age or older be screened by bone densitometry . Additionally they recommend screening younger women with risk factors. There

8360-589: Is required to completed a recognised course in safe use of bone mineral densitometers. In NSW and QLD a DXA technician only requires prior study in science, nursing or other related undergraduate study. The Environmental Protection Agency (EPA) oversees licensing of technicians, however, this is far from rigorous and regulation is non-existent. Osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass , micro-architectural deterioration of bone tissue leading to more porous bone, and consequent increase in fracture risk. It

8512-453: Is small, as low as 0.001 mSv , much less than a standard chest or dental x-ray. However, the dose delivered by older DEXA radiation sources (that used radioisotopes rather than x-ray generators ) could be as high as 35 mGy, considered a significant dose by radiological health standards. The quality of DXA operators varies widely. DXA is not regulated like other radiation-based imaging techniques because of its low dosage. Each US state has

8664-422: Is sometimes the best medicine. Resistance training is the most recommended method of physical activity but that can come in multiple forms. High intensity and high impact training is shown to be extremely beneficial in improving bone health and the most effective in improving, maintaining, bone density in the lower spine and femur. Although these types of exercises are safe for postmenopausal women, there still may be

8816-408: Is the acceleration due to Earth's gravitational field , (expressed as the acceleration experienced by a free-falling object). For other situations, such as when objects are subjected to mechanical accelerations from forces other than the resistance of a planetary surface, the weight force is proportional to the mass of an object multiplied by the total acceleration away from free fall, which is called

8968-430: Is the basis by which masses are determined by weighing . In simple spring scales , for example, the force F is proportional to the displacement of the spring beneath the weighing pan, as per Hooke's law , and the scales are calibrated to take g into account, allowing the mass M to be read off. Assuming the gravitational field is equivalent on both sides of the balance, a balance measures relative weight, giving

9120-427: Is the gravitational mass ( standard gravitational parameter ) of the body causing gravitational fields, and R is the radial coordinate (the distance between the centers of the two bodies). By finding the exact relationship between a body's gravitational mass and its gravitational field, Newton provided a second method for measuring gravitational mass. The mass of the Earth can be determined using Kepler's method (from

9272-411: Is the most common reason for a broken bone among the elderly . Bones that commonly break include the vertebrae in the spine , the bones of the forearm , the wrist , and the hip . Until a broken bone occurs there are typically no symptoms. Bones may weaken to such a degree that a break may occur with minor stress or spontaneously. After the broken bone heals, some people may have chronic pain and

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9424-513: Is the sponge-like bone in the ends of long bones and vertebrae. Cortical bone is the hard outer shell of bones and the middle of long bones. Because osteoblasts and osteoclasts inhabit the surface of bones, trabecular bone is more active and is more subject to bone turnover and remodeling. Not only is bone density decreased, but the microarchitecture of bone is also disrupted. The weaker spicules of trabecular bone break ("microcracks"), and are replaced by weaker bone. Common osteoporotic fracture sites,

9576-560: Is theoretically modifiable, although in many cases, the use of medication that increases osteoporosis risk may be unavoidable. Caffeine is not a risk factor for osteoporosis. Many diseases and disorders have been associated with osteoporosis. For some, the underlying mechanism influencing the bone metabolism is straightforward, whereas for others the causes are multiple or unknown. Certain medications have been associated with an increase in osteoporosis risk; only glucocorticosteroids and anticonvulsants are classically associated, but evidence

9728-410: Is theoretically possible to collect an immense number of small objects and form them into an enormous gravitating sphere. However, from a practical standpoint, the gravitational fields of small objects are extremely weak and difficult to measure. Newton's books on universal gravitation were published in the 1680s, but the first successful measurement of the Earth's mass in terms of traditional mass units,

9880-702: Is typically measured by dual-energy X-ray absorptiometry (DXA or DEXA). Prevention of osteoporosis includes a proper diet during childhood, hormone replacement therapy for menopausal women, and efforts to avoid medications that increase the rate of bone loss. Efforts to prevent broken bones in those with osteoporosis include a good diet, exercise, and fall prevention . Lifestyle changes such as stopping smoking and not drinking alcohol may help. Bisphosphonate medications are useful to decrease future broken bones in those with previous broken bones due to osteoporosis. In those with osteoporosis but no previous broken bones, they are less effective. They do not appear to affect

10032-467: The Cavendish experiment , did not occur until 1797, over a hundred years later. Henry Cavendish found that the Earth's density was 5.448 ± 0.033 times that of water. As of 2009, the Earth's mass in kilograms is only known to around five digits of accuracy, whereas its gravitational mass is known to over nine significant figures. Given two objects A and B, of masses M A and M B , separated by

10184-658: The European Union had osteoporosis in 2010. In the United States in 2010, about 8 million women and between 1 and 2 million men had osteoporosis. White and Asian people are at greater risk. The word "osteoporosis" is from the Greek terms for "porous bones". Osteoporosis has no symptoms and the person usually does not know that they have osteoporosis until a bone is broken. Osteoporotic fractures occur in situations where healthy people would not normally break

10336-471: The International Society for Clinical Densitometry (ISCD) is that a patient may be tested for BMD if they have a condition that could precipitate bone loss, is going to be prescribed pharmaceuticals known to cause bone loss, or is being treated and needs to be monitored. The ISCD states that there is no clearly understood correlation between BMD and the risk of a child's sustaining a fracture;

10488-543: The Solar System . On 25 August 1609, Galileo Galilei demonstrated his first telescope to a group of Venetian merchants, and in early January 1610, Galileo observed four dim objects near Jupiter, which he mistook for stars. However, after a few days of observation, Galileo realized that these "stars" were in fact orbiting Jupiter. These four objects (later named the Galilean moons in honor of their discoverer) were

10640-550: The Standard Model . The concept of amount is very old and predates recorded history . The concept of "weight" would incorporate "amount" and acquire a double meaning that was not clearly recognized as such. What we now know as mass was until the time of Newton called “weight.” ... A goldsmith believed that an ounce of gold was a quantity of gold. ... But the ancients believed that a beam balance also measured “heaviness” which they recognized through their muscular senses. ... Mass and its associated downward force were believed to be

10792-686: The Wnt signaling pathway is recognized, but less well understood. Local production of eicosanoids and interleukins is thought to participate in the regulation of bone turnover, and excess or reduced production of these mediators may underlie the development of osteoporosis. Osteoclast maturation and activity is also regulated by activation of colony stimulating factor 1 receptor (CSF1R). Menopause -associated increase production of TNF-α stimulates stromal cells to produce colony stimulating factor 1 (CSF-1) which activates CSF1R and stimulates osteoclasts to reabsorb bone. Trabecular bone (or cancellous bone)

10944-404: The bone mineral density (BMD). The most popular method of measuring BMD is dual-energy X-ray absorptiometry . In addition to the detection of abnormal BMD, the diagnosis of osteoporosis requires investigations into potentially modifiable underlying causes; this may be done with blood tests . Depending on the likelihood of an underlying problem, investigations for cancer with metastasis to

11096-405: The carob seed ( carat or siliqua ) as a measurement standard. If an object's weight was equivalent to 1728 carob seeds , then the object was said to weigh one Roman pound. If, on the other hand, the object's weight was equivalent to 144 carob seeds then the object was said to weigh one Roman ounce (uncia). The Roman pound and ounce were both defined in terms of different sized collections of

11248-495: The elementary charge . Non-SI units accepted for use with SI units include: Outside the SI system, other units of mass include: In physical science , one may distinguish conceptually between at least seven different aspects of mass , or seven physical notions that involve the concept of mass . Every experiment to date has shown these seven values to be proportional , and in some cases equal, and this proportionality gives rise to

11400-442: The melting point of ice. However, because precise measurement of a cubic decimetre of water at the specified temperature and pressure was difficult, in 1889 the kilogram was redefined as the mass of a metal object, and thus became independent of the metre and the properties of water, this being a copper prototype of the grave in 1793, the platinum Kilogramme des Archives in 1799, and the platinum–iridium International Prototype of

11552-446: The osteoblast and toward the marrow adipocyte lineage. An interplay of these three mechanisms underlies the development of fragile bone tissue. Hormonal factors strongly determine the rate of bone resorption; lack of estrogen (e.g. as a result of menopause) increases bone resorption, as well as decreasing the deposition of new bone that normally takes place in weight-bearing bones. The amount of estrogen needed to suppress this process

11704-416: The proper acceleration . Through such mechanisms, objects in elevators, vehicles, centrifuges, and the like, may experience weight forces many times those caused by resistance to the effects of gravity on objects, resulting from planetary surfaces. In such cases, the generalized equation for weight W of an object is related to its mass m by the equation W = – ma , where a is the proper acceleration of

11856-453: The torsion balance pendulum, in 1889. As of 2008 , no deviation from universality, and thus from Galilean equivalence, has ever been found, at least to the precision 10 . More precise experimental efforts are still being carried out. The universality of free-fall only applies to systems in which gravity is the only acting force. All other forces, especially friction and air resistance , must be absent or at least negligible. For example, if

12008-444: The "Galilean equivalence principle" or the " weak equivalence principle " has the most important consequence for freely falling objects. Suppose an object has inertial and gravitational masses m and M , respectively. If the only force acting on the object comes from a gravitational field g , the force on the object is: Given this force, the acceleration of the object can be determined by Newton's second law: Putting these together,

12160-400: The 17th century have demonstrated that inertial and gravitational mass are identical; since 1915, this observation has been incorporated a priori in the equivalence principle of general relativity . The International System of Units (SI) unit of mass is the kilogram (kg). The kilogram is 1000 grams (g), and was first defined in 1795 as the mass of one cubic decimetre of water at

12312-753: The ACSM general training principle to better design a program for the individual. Which mode of exercise and dosage has been a recurring question for treating osteoporosis, many articles have found that multimodal exercise programs have had findings of significant improvement in factors related to osteoporosis. Factors include lower limb strength, balance, flexibility, and risk of falls. Other modes of exercise have also proven to improve individuals with osteoporosis, some of these modes include weight-bearing, resistance specifically progressive resistance, and aerobic exercise. The recommendations for these types of exercises are as follows, weight-bearing exercise should be done 4-7 days

12464-675: The Kilogram (IPK) in 1889. However, the mass of the IPK and its national copies have been found to drift over time. The re-definition of the kilogram and several other units came into effect on 20 May 2019, following a final vote by the CGPM in November 2018. The new definition uses only invariant quantities of nature: the speed of light , the caesium hyperfine frequency , the Planck constant and

12616-449: The absorption by soft tissue, leaving just the absorption by bone, which is related to bone density. One type of DXA scanner uses a cerium filter with a tube voltage of 80 kV , resulting in effective photon energies of about 40 and 70 keV . There is also a DXA scanner type using a samarium filter with a tube voltage of 100 kV, resulting in effective energies of 47 and 80 keV. Also, the tube voltage can be continuously switched between

12768-428: The abstract concept of mass. There are a number of ways mass can be measured or operationally defined : In everyday usage, mass and " weight " are often used interchangeably. For instance, a person's weight may be stated as 75 kg. In a constant gravitational field, the weight of an object is proportional to its mass, and it is unproblematic to use the same unit for both concepts. But because of slight differences in

12920-885: The accuracy. The U.S. Preventive Services Task Force recommends that women over the age of 65 should get a DXA scan. The date at which men should be tested is uncertain but some sources recommend age 70. At risk women should consider getting a scan when their risk is equal to that of a normal 65-year-old woman. A person's risk can be measured using the University of Sheffield's FRAX calculator, which includes many different clinical risk factors including prior fragility fracture, use of glucocorticoids , heavy smoking, excess alcohol intake, rheumatoid arthritis, history of parental hip fracture, chronic renal and liver disease, chronic respiratory disease, long-term use of phenobarbital or phenytoin, celiac disease, inflammatory bowel disease, and other risks. The World Health Organization has defined

13072-448: The area (also measured by the machine) of the site being scanned. Because DXA calculates BMD using area (aBMD: areal Bone Mineral Density), it is not an accurate measurement of true bone mineral density, which is mass divided by a volume . In order to distinguish DXA BMD from volumetric bone-mineral density, researchers sometimes refer to DXA BMD as an areal bone mineral density (aBMD). The confounding effect of differences in bone size

13224-501: The basis of densitometric criteria alone. It also states, for premenopausal women, Z-scores (comparison with age group rather than peak bone mass) rather than T-scores should be used, and the diagnosis of osteoporosis in such women also should not be made on the basis of densitometric criteria alone. Chemical biomarkers are a useful tool in detecting bone degradation. The enzyme cathepsin K breaks down type-I collagen , an important constituent in bones. Prepared antibodies can recognize

13376-732: The blood. The role of calcitonin , a hormone generated by the thyroid that increases bone deposition, is less clear and probably not as significant as that of PTH. The activation of osteoclasts is regulated by various molecular signals, of which RANKL (receptor activator of nuclear factor kappa-B ligand) is one of the best-studied. This molecule is produced by osteoblasts and other cells (e.g. lymphocytes ), and stimulates RANK (receptor activator of nuclear factor κB). Osteoprotegerin (OPG) binds RANKL before it has an opportunity to bind to RANK, and hence suppresses its ability to increase bone resorption. RANKL, RANK, and OPG are closely related to tumor necrosis factor and its receptors. The role of

13528-501: The body will be attenuated by both soft tissue and bone, and it is not possible to determine, from a single beam, how much attenuation was attributable to the bone. However, the attenuation coefficients vary with the energy of the X-rays, and, crucially, the ratio of the attenuation coefficients also varies. DXA uses two energies of X-ray. The difference in total absorption between the two can be used, by suitable weighting, to subtract out

13680-663: The body. It has been suggested that, while very accurately measuring minerals and lean soft tissue (LST), DXA may provide skewed results due to its method of indirectly calculating fat mass by subtracting it from the LST and/or body cell mass (BCM) that DXA actually measures. DXA scans have been suggested as useful tools to diagnose conditions with an abnormal fat distribution, such as familial partial lipodystrophy . They are also used to assess adiposity in children, especially to conduct clinical research. DXA uses X-rays to measure bone mineral density. The radiation dose of current DEXA systems

13832-509: The bone matrix. These alterations in composition contribute to how bone can handle mechanical loading. Thus, osteoporosis-induced changes at the macroscopic and microscopic levels significantly impact the mechanical properties of bone, predisposing individuals to fractures even under relatively low mechanical loads. Understanding these structural alterations is vital for developing effective diagnostic and therapeutic strategies for osteoporosis. The underlying mechanism in all cases of osteoporosis

13984-455: The bone matrix. Low bone mass density can then occur when osteoclasts are degrading the bone matrix faster than the osteoblasts are rebuilding the bone. The three main mechanisms by which osteoporosis develops are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodeling, likely due to mesenchymal stem cells biasing away from

14136-434: The bone's volume, and are, therefore, not susceptible to the confounding effect of bone-size in the way that DXA results are susceptible. It is important for patients to get repeat BMD measurements done on the same machine each time, or at least a machine from the same manufacturer. Error between machines, or trying to convert measurements from one manufacturer's standard to another can introduce errors large enough to wipe out

14288-521: The bone, multiple myeloma, Cushing's disease and other above-mentioned causes may be performed. Conventional radiography is useful, both by itself and in conjunction with CT or MRI, for detecting complications of osteopenia (reduced bone mass; pre-osteoporosis), such as fractures; for differential diagnosis of osteopenia; or for follow-up examinations in specific clinical settings, such as soft tissue calcifications, secondary hyperparathyroidism, or osteomalacia in renal osteodystrophy. However, radiography

14440-405: The classical theory offers no compelling reason why the gravitational mass has to equal the inertial mass. That it does is merely an empirical fact. Albert Einstein developed his general theory of relativity starting with the assumption that the inertial and passive gravitational masses are the same. This is known as the equivalence principle . The particular equivalence often referred to as

14592-479: The community who had no known history of vitamin D deficiency, osteoporosis, or a fracture. The USPSTF does not recommend low dose supplementation (less than 1 g of calcium and 400 IU of vitamin D) in postmenopausal women as there does not appear to be a difference in fracture risk. A 2015 review found little data that supplementation of calcium decreases the risk of fractures. While some meta-analyses have found

14744-437: The development of osteoporosis through therapeutic exercise. Prescribed amounts of mechanical loading or increased forces on the bones promote bone formation and vascularization in various ways, therefore offering a preventative measure that is not reliant on drugs. Specific exercise interacts with the body's hormones and signaling pathways which encourages the maintenance of a healthy skeleton. Reduced estrogen levels increase

14896-637: The diagnosis of osteoporosis in children cannot be made using the basis of a densitometry criteria. T-scores are prohibited with children and should not even appear on DXA reports. Thus, the WHO classification of osteoporosis and osteopenia in adults cannot be applied to children, but Z-scores can be used to assist diagnosis. Some clinics may routinely carry out DXA scans on pediatric patients with conditions such as nutritional rickets , lupus , and Turner syndrome . DXA has been demonstrated to measure skeletal maturity and body fat composition and has been used to evaluate

15048-470: The double of the distance between the two bodies. Hooke urged Newton, who was a pioneer in the development of calculus , to work through the mathematical details of Keplerian orbits to determine if Hooke's hypothesis was correct. Newton's own investigations verified that Hooke was correct, but due to personal differences between the two men, Newton chose not to reveal this to Hooke. Isaac Newton kept quiet about his discoveries until 1684, at which time he told

15200-422: The effects of pharmaceutical therapy. It may also aid pediatricians in diagnosing and monitoring treatment of disorders of bone mass acquisition in childhood. However, it seems that DXA is still in its early days in pediatrics, and there are widely acknowledged limitations and disadvantages with DXA. A view exists that DXA scans for diagnostic purposes should not even be performed outside specialist centers, and, if

15352-434: The elapsed time could be measured. The ball was allowed to roll a known distance down the ramp, and the time taken for the ball to move the known distance was measured. The time was measured using a water clock described as follows: Galileo found that for an object in free fall, the distance that the object has fallen is always proportional to the square of the elapsed time: Galileo had shown that objects in free fall under

15504-515: The elderly is often attributed to fractures from osteoporosis and can lead to further disability and early mortality. These fractures may also be asymptomatic. The most common osteoporotic fractures are of the wrist, spine, shoulder and hip. The symptoms of a vertebral collapse (" compression fracture ") are sudden back pain , often with radicular pain (shooting pain due to nerve root compression) and rarely with spinal cord compression or cauda equina syndrome . Multiple vertebral fractures lead to

15656-407: The evidence shows no adverse effect of higher protein intake on bone health. Evidence suggests that exercise can help promote bone health in older people. In particular, physical exercise can be beneficial for bone density in postmenopausal women, and lead to a slightly reduced risk of a bone fracture (absolute difference 4%). Weight bearing exercise has been found to cause an adaptive response in

15808-497: The exact number of carob seeds that would be required to produce a gravitational field similar to that of the Earth or Sun. In fact, by unit conversion it is a simple matter of abstraction to realize that any traditional mass unit can theoretically be used to measure gravitational mass. Measuring gravitational mass in terms of traditional mass units is simple in principle, but extremely difficult in practice. According to Newton's theory, all objects produce gravitational fields and it

15960-410: The feather should hit the ground at exactly the same time (assuming the acceleration of both objects towards each other, and of the ground towards both objects, for its own part, is negligible). This can easily be done in a high school laboratory by dropping the objects in transparent tubes that have the air removed with a vacuum pump. It is even more dramatic when done in an environment that naturally has

16112-399: The fibrils being arranged into different patterns such as lamellae. The microstructure of bone then forms vascular channels, called osteons, which are surrounded by lamellae. At the subsequent scale of bones, there are different types of bone based on morphology: cortical (solid), cancellous (sponge), or trabecular (thin plates).   A basic picture of the hierarchical structure of bones

16264-411: The financial costs to health care systems. The risk of having osteoporosis includes age and sex. Risk factors include both nonmodifiable (for example, age and some medications that may be necessary to treat a different condition) and modifiable (for example, alcohol use, smoking, vitamin deficiency). In addition, osteoporosis is a recognized complication of specific diseases and disorders. Medication use

16416-404: The first celestial bodies observed to orbit something other than the Earth or Sun. Galileo continued to observe these moons over the next eighteen months, and by the middle of 1611, he had obtained remarkably accurate estimates for their periods. Sometime prior to 1638, Galileo turned his attention to the phenomenon of objects in free fall, attempting to characterize these motions. Galileo was not

16568-402: The first paragraph of Principia , Newton defined quantity of matter as “density and bulk conjunctly”, and mass as quantity of matter. The quantity of matter is the measure of the same, arising from its density and bulk conjunctly. ... It is this quantity that I mean hereafter everywhere under the name of body or mass. And the same is known by the weight of each body; for it is proportional to

16720-436: The first to investigate Earth's gravitational field, nor was he the first to accurately describe its fundamental characteristics. However, Galileo's reliance on scientific experimentation to establish physical principles would have a profound effect on future generations of scientists. It is unclear if these were just hypothetical experiments used to illustrate a concept, or if they were real experiments performed by Galileo, but

16872-404: The following categories based on bone density in white women: Bone densities are often given to patients as a T score or a Z score. A T score tells the patient what their bone mineral density is in comparison to a young adult of the same gender with peak bone mineral density. A normal T score is -1.0 and above, low bone density is between -1.0 and -2.5, and osteoporosis is -2.5 and lower. A Z score

17024-572: The gap between Galileo's gravitational acceleration and Kepler's elliptical orbits. It appeared in Newton's 1728 book A Treatise of the System of the World . According to Galileo's concept of gravitation, a dropped stone falls with constant acceleration down towards the Earth. However, Newton explains that when a stone is thrown horizontally (meaning sideways or perpendicular to Earth's gravity) it follows

17176-421: The gravitational acceleration is given by: This says that the ratio of gravitational to inertial mass of any object is equal to some constant K if and only if all objects fall at the same rate in a given gravitational field. This phenomenon is referred to as the "universality of free-fall". In addition, the constant K can be taken as 1 by defining our units appropriately. The first experiments demonstrating

17328-472: The head. Lastly, aerobic exercise has minimal effect on preventing BMD loss unless done at a higher intensity or with a load like a weighted vest. Considerations with this mode are that this may cause a higher risk of fall or fracture. Improvements can also be observed in other ways, such as decreased Timed-Up-and-Go, increased Sit-To-Stand, and increased One-Leg-Stance-Test. A study with a 12-week exercise intervention on postmenopausal osteoporotic women observed

17480-416: The individual with osteoporosis refrained from consuming excess alcohol and to avoid smoking. These individuals should also be intentional about intaking an adequate amount of protein, calcium, and vitamin D. If the woman has an even higher risk of fracture, managing this may require therapy. Generally, the recommended treatment of prevention for a decrease in bone mineral density is physical activity. Exercise

17632-597: The individual’s need this can be attained by conducting a pre-exercise evaluation or screening, exercise should also be tailored to the individual and what works for them. Important things often overlooked when treating osteoporosis are muscle strength and maintenance of BMD, which should be incorporated into the program to optimize the benefits of exercise. This entails including exercises that focus on and improve muscle strength and exercises that focus on and improve skeletal strength or BMD as these go hand in hand for reducing fall and fracture risk. It’s also important to reference

17784-629: The influence of the Earth's gravitational field have a constant acceleration, and Galileo's contemporary, Johannes Kepler, had shown that the planets follow elliptical paths under the influence of the Sun's gravitational mass. However, Galileo's free fall motions and Kepler's planetary motions remained distinct during Galileo's lifetime. According to K. M. Browne: "Kepler formed a [distinct] concept of mass ('amount of matter' ( copia materiae )), but called it 'weight' as did everyone at that time." Finally, in 1686, Newton gave this distinct concept its own name. In

17936-460: The interpretation of BMD as measured by DXA. One important confounding variable is bone size. DXA has been shown to overestimate the bone mineral density of taller subjects and underestimate the bone mineral density of smaller subjects. This error is due to the way by which DXA calculates BMD. In DXA, bone mineral content (measured as the attenuation of the X-ray by the bones being scanned) is divided by

18088-424: The limitations of DXA and QCT. Quantitative ultrasound has many advantages in assessing osteoporosis. The modality is small, no ionizing radiation is involved, measurements can be made quickly and easily, and the cost of the device is low compared with DXA and QCT devices. The calcaneus is the most common skeletal site for quantitative ultrasound assessment because it has a high percentage of trabecular bone that

18240-455: The living environment may substantially reduce falls. Those with previous falls, as well as those with gait or balance disorders, are most at risk. As well as susceptibility to breaks and fractures, osteoporosis can lead to other complications. Bone fractures from osteoporosis can lead to disability and an increased risk of death after the injury in elderly people. Osteoporosis can decrease the quality of life, increase disabilities, and increase

18392-511: The mean average mortality rate within one year for Europe being 23.3%, for Asia 17.9%, United States 21% and Australia 24.9%. Fracture risk calculators assess the risk of fracture based upon several criteria, including bone mineral density , age, smoking, alcohol usage, weight, and gender. Recognized calculators include FRAX , the Garvan FRC calculator and QFracture as well as the open access FREM tool. The FRAX tool can also be applied in

18544-558: The motion of bodies in an orbit"). Halley presented Newton's findings to the Royal Society of London, with a promise that a fuller presentation would follow. Newton later recorded his ideas in a three-book set, entitled Philosophiæ Naturalis Principia Mathematica (English: Mathematical Principles of Natural Philosophy ). The first was received by the Royal Society on 28 April 1685–86; the second on 2 March 1686–87; and

18696-403: The nearby gravitational field. No matter how strong the gravitational field, objects in free fall are weightless , though they still have mass. The force known as "weight" is proportional to mass and acceleration in all situations where the mass is accelerated away from free fall. For example, when a body is at rest in a gravitational field (rather than in free fall), it must be accelerated by

18848-509: The object caused by all influences other than gravity. (Again, if gravity is the only influence, such as occurs when an object falls freely, its weight will be zero). Although inertial mass, passive gravitational mass and active gravitational mass are conceptually distinct, no experiment has ever unambiguously demonstrated any difference between them. In classical mechanics , Newton's third law implies that active and passive gravitational mass must always be identical (or at least proportional), but

19000-430: The object from going into free fall. By contrast, on the surface of the Moon, the same object still has a mass of 50 kilograms but weighs only 81.5 newtons, because only 81.5 newtons is required to keep this object from going into a free fall on the moon. Restated in mathematical terms, on the surface of the Earth, the weight W of an object is related to its mass m by W = mg , where g = 9.80665 m/s

19152-412: The orbit of Earth's Moon), or it can be determined by measuring the gravitational acceleration on the Earth's surface, and multiplying that by the square of the Earth's radius. The mass of the Earth is approximately three-millionths of the mass of the Sun. To date, no other accurate method for measuring gravitational mass has been discovered. Newton's cannonball was a thought experiment used to bridge

19304-408: The ovaries . Certain medications increase the rate of bone loss, including some antiseizure medications , chemotherapy , proton pump inhibitors , selective serotonin reuptake inhibitors , and glucocorticosteroids . Smoking and getting an inadequate amount of exercise are also risk factors. Osteoporosis is defined as a bone density of 2.5 standard deviations below that of a young adult. This

19456-409: The planets orbit the Sun. In Kepler's final planetary model, he described planetary orbits as following elliptical paths with the Sun at a focal point of the ellipse . Kepler discovered that the square of the orbital period of each planet is directly proportional to the cube of the semi-major axis of its orbit, or equivalently, that the ratio of these two values is constant for all planets in

19608-466: The polymorphisms of GGCX could explain the individual variation in the response to treatment of vitamin K. Dietary sources of calcium include dairy products, leafy greens, legumes, and beans. There has been conflicting evidence about whether or not dairy is an adequate source of calcium to prevent fractures. The National Academy of Sciences recommends 1,000 mg of calcium for those aged 19–50, and 1,200 mg for those aged 50 and above. A review of

19760-400: The presence of an applied force. The inertia and the inertial mass describe this property of physical bodies at the qualitative and quantitative level respectively. According to Newton's second law of motion , if a body of fixed mass m is subjected to a single force F , its acceleration a is given by F / m . A body's mass also determines the degree to which it generates and is affected by

19912-446: The production of Insulin-like growth factors in the bone, but at a greater extent. Post-menopausal women experience a reduction of estrogen, which is essential for density, so these exercise-induced hormonal enhancements can counteract the loss of bone mineral density in the most critical area, like the lumbar spine and the femoral neck. Research suggest that regular resistance training accompanied with weight-bearing activities help reduce

20064-563: The progression of osteoporosis and risk of fracture. Mass Mass is an intrinsic property of a body . It was traditionally believed to be related to the quantity of matter in a body, until the discovery of the atom and particle physics . It was found that different atoms and different elementary particles , theoretically with the same amount of matter, have nonetheless different masses. Mass in modern physics has multiple definitions which are conceptually distinct, but physically equivalent. Mass can be experimentally defined as

20216-402: The rate of bone loss through home exercise programs. Whole body vibration therapy has also been suggested as a physical therapy intervention. Moderate to low-quality evidence indicates that whole body vibration therapy may reduce the risk of falls. There are conflicting reviews as to whether vibration therapy improves bone mineral density. Physical therapy can aid in overall prevention in

20368-521: The reference data of adults (to calculate a T-score) will underestimate the BMD of children, because children have less bone mass than fully developed adults. This would lead to an over-diagnosis of osteopenia for children. To avoid an overestimation of bone mineral deficits, BMD scores are commonly compared to reference data for the same gender and age (by calculating a Z-score ). Also, there are other variables in addition to age that are suggested to confound

20520-464: The relative gravitation mass of each object. Mass was traditionally believed to be a measure of the quantity of matter in a physical body, equal to the "amount of matter" in an object. For example, Barre´ de Saint-Venant argued in 1851 that every object contains a number of "points" (basically, interchangeable elementary particles), and that mass is proportional to the number of points the object contains. (In practice, this "amount of matter" definition

20672-544: The release of growth hormone and Insulin-like growth factor-1 or IGF-1 that participate in bone remodeling. Stress is applied to the bones, thus activating osteoblast, which are cells that form new bones and grow and heal existing bones while restoring hormones that increase bone density. Resistance training exercises, like weight lifting, can lead to brief increased in anabolic hormones, like testosterone, which aid in muscle and bone strength. The increase in mechanical tension during resistance exercise will likely help stimulate

20824-567: The resulting fragment, called a neoepitope , as a way to diagnose osteoporosis. Increased urinary excretion of C-telopeptides , a type-I collagen breakdown product, also serves as a biomarker for osteoporosis. Quantitative computed tomography (QCT) differs from DXA in that it gives separate estimates of BMD for trabecular and cortical bone and reports precise volumetric mineral density in mg/cm rather than BMD's relative Z-score. Among QCT's advantages: it can be performed at axial and peripheral sites, can be calculated from existing CT scans without

20976-554: The results obtained from these experiments were both realistic and compelling. A biography by Galileo's pupil Vincenzo Viviani stated that Galileo had dropped balls of the same material, but different masses, from the Leaning Tower of Pisa to demonstrate that their time of descent was independent of their mass. In support of this conclusion, Galileo had advanced the following theoretical argument: He asked if two bodies of different masses and different rates of fall are tied by

21128-406: The risk of death. Osteoporosis becomes more common with age. About 15% of Caucasians in their 50s and 70% of those over 80 are affected. It is more common in women than men. In the developed world , depending on the method of diagnosis, 2% to 8% of males and 9% to 38% of females are affected. Rates of disease in the developing world are unclear. About 22 million women and 5.5 million men in

21280-525: The risk of osteoporosis, so hormone replacement therapy when women reach the menopause may reduce the incidence of osteoporosis. A more natural way of restoring hormone levels in postmenopausal women include participating in specific forms of exercise. Weight-bearing exercises and resistance training exercises such as squats with weights, step-ups, lunges, stair climbing, and even jogging can elicit hormone responses that are advantageous for post-menopausal women living with osteoporosis. These exercises result in

21432-503: The same common mass standard, the carob seed. The ratio of a Roman ounce (144 carob seeds) to a Roman pound (1728 carob seeds) was: In 1600 AD, Johannes Kepler sought employment with Tycho Brahe , who had some of the most precise astronomical data available. Using Brahe's precise observations of the planet Mars, Kepler spent the next five years developing his own method for characterizing planetary motion. In 1609, Johannes Kepler published his three laws of planetary motion, explaining how

21584-407: The same thing. Humans, at some early era, realized that the weight of a collection of similar objects was directly proportional to the number of objects in the collection: where W is the weight of the collection of similar objects and n is the number of objects in the collection. Proportionality, by definition, implies that two values have a constant ratio : An early use of this relationship

21736-430: The sensitivity of the measurements. DXA results need to be adjusted if the patient is taking strontium supplements. DXA can also used to measure trabecular bone score . DXA is, by far, the most widely used technique for bone mineral density measurements, since it is considered to be cheap, accessible, easy to use, and able to provide an accurate estimation of bone mineral density in adults. The official position of

21888-790: The skeleton, promoting osteoblast activity and protecting bone density. A position statement concluded that increased bone activity and weight-bearing exercises at a young age prevent bone fragility in adults. Limitations in the available evidence hinder the production of detailed evidence-based exercise recommendations. Some expert consensus guidance does exist. International guidelines recommend multicomponent exercise tailored to individual needs that includes "balance and mobility training, paired with weight bearing exercise, progressive resistance training, and posture exercises" (generally accompanied by optimal nutrition). Cycling and swimming are not considered weight-bearing exercise, and neither helps slow age-related bone loss (professional bicycle racing has

22040-441: The square of the distance to the body's center. For example, according to Newton's theory of universal gravitation, each carob seed produces a gravitational field. Therefore, if one were to gather an immense number of carob seeds and form them into an enormous sphere, then the gravitational field of the sphere would be proportional to the number of carob seeds in the sphere. Hence, it should be theoretically possible to determine

22192-399: The stiffness and strength compared to health bone. Additionally, bone mineral density (BMD) is a parameter used to evaluate fracture risk in bones and is used as a predictor of osteoporosis. A lower BMD value correlates to decreased bone and a higher bone fragility. Furthermore, bone diseases, such as osteoporosis, are known to alter the composition of collagen and other proteins that make up

22344-501: The strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets. Conceptually, "mass" (measured in kilograms ) refers to an intrinsic property of an object, whereas "weight" (measured in newtons ) measures an object's resistance to deviating from its current course of free fall , which can be influenced by

22496-500: The third on 6 April 1686–87. The Royal Society published Newton's entire collection at their own expense in May 1686–87. Isaac Newton had bridged the gap between Kepler's gravitational mass and Galileo's gravitational acceleration, resulting in the discovery of the following relationship which governed both of these: where g is the apparent acceleration of a body as it passes through a region of space where gravitational fields exist, μ

22648-492: The top of a high mountain" with sufficient velocity, "it would reach at last quite beyond the circumference of the Earth, and return to the mountain from which it was projected." In contrast to earlier theories (e.g. celestial spheres ) which stated that the heavens were made of entirely different material, Newton's theory of mass was groundbreaking partly because it introduced universal gravitational mass : every object has gravitational mass, and therefore, every object generates

22800-459: The universality of free-fall were—according to scientific 'folklore'—conducted by Galileo obtained by dropping objects from the Leaning Tower of Pisa . This is most likely apocryphal: he is more likely to have performed his experiments with balls rolling down nearly frictionless inclined planes to slow the motion and increase the timing accuracy. Increasingly precise experiments have been performed, such as those performed by Loránd Eötvös , using

22952-535: The weight. Robert Hooke had published his concept of gravitational forces in 1674, stating that all celestial bodies have an attraction or gravitating power towards their own centers, and also attract all the other celestial bodies that are within the sphere of their activity. He further stated that gravitational attraction increases by how much nearer the body wrought upon is to its own center. In correspondence with Isaac Newton from 1679 and 1680, Hooke conjectured that gravitational forces might decrease according to

23104-458: The wrist, the hip, and the spine, have a relatively high trabecular bone to cortical bone ratio. These areas rely on the trabecular bone for strength, so the intense remodeling causes these areas to degenerate most when the remodeling is imbalanced. Around the ages of 30–35, cancellous or trabecular bone loss begins. Women may lose as much as 50%, while men lose about 30%. Osteoporosis can be diagnosed using conventional radiography and by measuring

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