1.Overview
Currently, about 200 million people worldwide suffer from osteoporosis, of which about 1.5 million patients suffer from fractures every year, including about 1/3 of vertebral fractures, 1/5 of hip fractures, 1/6 of wrist fractures, and 1/6 of other fractures. about 20% of patients with fractures are bedridden within one year due to respiratory, cardiac, and cerebrovascular diseases, which eventually lead to death [1]. Most of the current research on osteoporosis treatment is currently focused on internal medicine, which is difficult to promote due to the use of estrogen, calcium, active vitamins, calcitonin and fluoride, although they have certain efficacy, but the side effects are large and expensive. The WHO has clearly mentioned three major principles for the treatment of OP: calcium supplementation, exercise therapy and diet modification.
1.1 Definition Osteoporosis (OP) was first proposed by Pommer in 1885, and was defined by the Fourth International Symposium on Osteoporosis in 1993 as a systemic bone disease characterized by a decrease in bone mass and deterioration of bone microstructure, resulting in increased bone fragility and fracture. It is characterized by a decrease in bone mass, including a decrease in the proportion of bone mineral and bone matrix; a series of bone microstructure degeneration phenomena such as bone resorption, thinning, thinning and even fracture of bone trabeculae; an increase in bone brittleness, a decrease in strength, and a decrease in the ability to withstand the original load, which makes it easy to fracture even under the action of small external forces. This shows that osteoporosis is not a disease, but a state. Figure 1 clearly demonstrates the essence of osteoporosis, i.e., the reduction of bone mass, while the ratio of mineral to organic matter in bone tissue is normal.
1.2 Classification According to the extent of the lesion, OP can be divided into systemic osteoporosis and limited osteoporosis. We mainly discuss systemic osteoporosis here. It includes.
(1) primary (physiological) osteoporosis
It is a physiological degenerative lesion that must occur with age and is the most common type. Among them, it can be divided into two types, type I is postmenopausal osteoporosis, seen in postmenopausal women due to the decline in estrogen levels resulting in osteoporosis.
Type II is senile osteoporosis, which usually occurs in elderly people over 65 years of age.
Type I and type II often occur together
(2) Secondary osteoporosis. It is osteoporosis induced by other diseases or other causes. For example: hyperthyroidism, hyperadrenocorticism, diabetic osteoporosis, etc.
(3) Idiopathic osteoporosis. It is usually seen in adolescents or adults aged 8 to 14 years old, with family history and more females.
1.3 Etiology and pathogenesis of osteoporosis
The etiology of primary osteoporosis and its pathogenesis are still not well understood. Among the many possible causes of primary osteoporosis, most scholars now believe that estrogen deficiency and calcium are the main causes. The decrease in bone mass can be due to two factors: on the one hand, a decrease in bone formation; and on the other hand, an increase in bone resorption. Therefore various factors that can lead to a decrease in bone formation and an increase in bone resorption can lead to osteoporosis.
(1) Age factor
Primary osteoporosis is extremely common in the elderly. It is more common in women after menopause and in men after 55 years of age. The onset of osteoporosis is earlier and several times more common in women than in men.
(2) Endocrine factors
Estrogen can reduce bone resorption and increase the synthesis of organic matter in bone, providing a site for calcium salt deposition. After menopause, estrogen levels decline in women, leading to calcium deficiency and affecting the formation of organic matter, leading to osteoporosis. Decreased androgens affect protein formation and are one of the main causes of osteoporosis in older men. Other hormones associated with osteoporosis are parathyroid hormone, calcitonin and active vitamin D.
(3) Nutritional status
The daily requirement of the body is about 600-800mg of calcium. In postmenopausal women, the daily requirement is 1500mg, all of which must be taken from the diet. If calcium intake is not enough, in order to maintain the normal level of serum calcium, it should be extracted from the bone. The daily calcium intake of postmenopausal women in China is about 300-400 mg. Our diet leads to a long-term low-calcium diet which is the main cause of osteoporosis. Malnutrition can also cause severe protein deficiency, leading to osteoporosis.
(4) Lifestyle and mechanical activity
Physical activity has a great impact on bones. The more activity there is, the stronger the pulling force on the bone, which can promote the transformation of osteoclasts into osteoblasts and facilitate the formation of new bone. Long-term idleness and various reasons for disuse, due to insufficient mechanical stimulation of the bone, resulting in less bone formation and more bone resorption, resulting in osteoporosis. Fractures and bone disease can also lead to osteoporosis after long-term fixation. Lack of outdoor activities and insufficient sunlight leading to insufficient vitamin D are also causes of osteoporosis.
1.4 General principles of osteoporosis treatment
(1) Increasing bone mass and delaying bone loss
It is generally believed that bone mass growth occurs before the age of 20, and bone mass loss begins gradually after the age of 40. Therefore, during the age of bone growth, i.e., adolescence, one should actively participate in sports to maximize the peak bone mass and maintain it for a longer period of time.
Gao Ping, Xu Ling [3] et al. determined and analyzed the bone mineral density (BMD) values of male and female athletes in China who had been engaged in high-intensity training for more than 8 years, and found that the peak bone mineral density of both male and female athletes was higher than that of the general population at all tested sites, which was statistically significant. Zhao Jiexiu [4] et al. randomly selected 171 male students from the Department of Physical Education and the Department of Chemistry of South China Normal University and tested their BMD and body mass indexes, and the results showed that the sprint group, such as the martial arts group, had higher BMD values compared to the control group, and there was a highly significant difference (P<0.01). These findings suggest that exercise has a positive effect on peak bone mass accumulation, especially for adolescents at the growth stage, and that moderate exercise can reduce the occurrence of osteoporosis in the future by effectively increasing peak bone mass.
In the age of bone loss, i.e., after 40 years of age, especially around the time of menopause in women, efforts should be made to delay bone loss; in the stage of rapid bone loss, appropriate therapeutic and preventive measures should be taken. Zhang Lin et al [5] conducted a six-month study on 75 postmenopausal female teachers at Tsinghua University by implementing fitness exercises in the exercise group and the same daily life in the control group, and the results showed that the effect of exercise on the maintenance of bone mass in postmenopausal women mainly lies in the inhibition of the bone resorption process of bone metabolism.
(2) Prevention of fracture occurrence
Fracture is the most serious consequence of osteoporosis. The most effective measures to prevent fracture, in addition to maximizing peak bone mass and delaying bone loss, are to improve the living and transportation environment and to reduce the external conditions for falls. Moderate exercise can significantly improve muscle strength, enhance muscle control of joints, and reduce the chance of falls. At the same time, the increase of muscle strength can effectively reduce the rate of bone loss; exercise can significantly accelerate blood circulation, avoid stiffness of joints, effectively improve the regulatory ability of the nervous system, reduce falls, and reduce the risk of fracture.
(3) Symptomatic treatment
The symptoms and characteristics of pain and fracture can be treated with medication, physical and surgical measures.
2. Review of exercise therapy for osteoporosis
In 1947, a famous article by Asher entitled “Danger in bed” was published in the British Medical Journal. He pointed out that prolonged physical inactivity leads to severe bone loss [6]. This was later demonstrated from astronauts, as weightlessness is similar to inactivity. By measuring the BMD of athletes, it was found that they all had higher BMD than the general population. This confirms the positive effect of exercise from another side. In the last 20 years, most studies have been conducted on menopausal women and older adults, focusing on what types of exercise and what exercise programs are more effective in improving and maintaining BMD. However, the exact frequency, intensity and duration of exercise are still unclear. Currently, with the rise of molecular biology and cell biology, research on the bony effects of exercise is developing in depth. It has been found that different VD receptor genes affect the osseous effects of exercise, and people with bb-type receptors respond to exercise more than people with other genotypes [7]. That is to say, in the case of the same amount of exercise, the bone mineral density of people with VD receptor type bb is easier to improve and maintain than other types of people.
3. Mechanisms of the effect of exercise therapy
3.1 Stress effect of exercise
The stress produced by exercise on bones leads to specific deformation of bone tissue and stimulates both bone cells and osteoblasts. Experiments have shown that the mechanical stress applied to osteoblasts in vitro leads to an increase in DNA synthesis, followed by an increase in the synthesis of collagen, the expression product of DNA, which raises the level of bone mass, when the rate of bone formation is greater than that without exercise, so that exercise leads to an increase in bone mass and a consequent increase in BMD. In postmenopausal women and the elderly, exercise compensates to some extent for the large loss of bone mass and thus plays a role in maintaining bone mass levels.
3.2 Hormonal effects of exercise
Moderate exercise increases the levels of estrogen and testosterone, which act on bone by regulating endocrine, and Alaia concluded through her study on exercise and bone health that endocrine plays a very important role in maintaining normal bone metabolism [6]. Primarily, it can promote protein synthesis in bone, which increases the total amount of bone matrix, which in turn facilitates calcification. In particular, testosterone and estradiol promote bone growth, development, thicken the bone cortex, promote the retention and deposition of calcium, and accelerate the fusion of the long bone stem and epiphysis. Research shows that moderate exercise can promote the secretion of testosterone and estrogen. Therefore, long-term moderate exercise can promote bone metabolism and increase bone dense mass.
3.3 Calcium supplementation effect of exercise
Ca is an important nutrient for the skeletal system, and more than 99% of calcium in the human body exists in the bones. Studies have shown that calcium deficiency is one of the main causes of osteoporosis. Exercise increases the demand for Ca while increasing bone mass, i.e., it raises the threshold. Conversely, prolonged inactivity, such as bed rest or limb immobilization, decreases the demand for Ca in bone mass, at which point even large amounts of calcium supplementation will not have a significant effect. A large amount of calcium is excreted from the urine, thus reducing bone density. In addition, outdoor activities can receive sufficient sunlight, which increases vitamin D and thus promotes calcium absorption. It is also believed that after proper exercise the blood flow value of the bone cortex increases, which improves the blood supply to the bone tissue and thus promotes calcium absorption.
3.4 Muscle effect of exercise
FROST suggests that non-mechanical factors (calcium, vitamin D, hormones, etc.) are not the most important in the pathogenesis of osteoporosis, and that muscle mass (including muscle mass and muscle strength) under the regulation of the nervous system is an important factor in determining bone strength (including bone mass and bone structure). cadavers and found that the weight of vertebral ashes was significantly and positively correlated with lumbar muscle, and that lumbar muscle weight was a key determinant of vertebral bone ash mass [8].Chow (1986) and Pocock (1986) found that BMD of the lumbar spine and femur was related to maximum muscle strength, and also found that the corresponding bone mass in humans is a roughly constant proportional relationship, and that age-related and bone loss in women tends to be be accompanied by a corresponding decrease in muscle strength. Therefore, exercise maintains muscle strength while maintaining the corresponding bone mass.
4. Research on exercise prescription
4.1 Choice of exercise modality
Nawhall et al. found that the increase in running distance was not accompanied by an increase in BMD. Moreover, large weight-bearing (i.e., large stress on the skeleton) for a short period of time can lead to a significant increase in BMD values than small weight-bearing for a long period of time [9]. Similar conclusions were obtained from human studies, Heinonen et al. studied weightlifters, cross-country athletes, skiers and cyclists and found that weightlifters had much higher BMD in the lumbar spine, femoral neck, scapula and distal radius than the other groups and that weightlifters were trained for shorter periods of time than the other groups of athletes. It can be seen that large weight-bearing exercises are superior to small weight-bearing exercises in improving BMD. A Japanese study also found that the average bone salt content of the L2-L4 lumbar spine and the bone mineral content of the greater trochanter of the femur in sprinters exceeded that of long-distance runners when comparing the bone mineral content of sprinters and long-distance runners. This indicates that explosive exercise is more beneficial than endurance exercise in maintaining and increasing BMD. Our study by Jiexiu Zhao et al. found that sprinting, soccer, basketball, and middle and long-distance running sports had decreasing exercise intensity in that order, and the BMD of athletes participating in that sport also showed a decreasing trend in that order.
In summary, heavy weight-bearing, explosive exercise is more stressful to the skeleton than aerobic exercise, and therefore, these forms of exercise have advantages in maintaining and improving BMD. However, training in a purely heavy-weight, explosive manner can be detrimental to the circulatory system of the subject, especially in the elderly. Therefore, the exercise regimen recommended by the American College of Sports Medicine for OP prevention is strength training, fitness running and walking. Accordingly, if we consider the prevention of OP from this point of view, can we consider the improvement of the common fitness methods of our elderly people. Most of the exercises for the elderly in China are based on slow walking, jogging, and qigong. If the physical condition allows, appropriate use of large load, explosive training methods, such as running, you can use weight running or fast running, using a comprehensive trainer fitness, you can use a medium to large load or explosive form of exercise. This will be of great benefit to maintain their BMD.
4.2 The choice of exercise program
Researchers have studied the BMD of athletes engaged in various sports and found that tennis players have significantly higher BMD in the hands and forearms, male swimmers have significantly higher BMD in the forearms and spine, running and climbing athletes have significantly higher BMD in the heel bone, and weightlifting and rowing athletes have significantly higher BMD in the forearms. These suggest that each sport has its own specific site for the increase in BMD. The increase in BMD correlates with the bones attached to the major muscle groups used in the sport, meaning that the BMD of the most commonly used bones is more likely to increase. Therefore, the choice of exercise program should be purposeful, based on the purpose of the exercise, the characteristics of the exercise program, and interests to choose. Some studies have shown that stair climbing is an effective exercise program to increase the BMD of the proximal femur because it produces a greater instantaneous stress stimulus to the femur. Therefore, if you want to prevent hip fracture, stair climbing is a suitable exercise program. Another study found that the bone density of the lumbar spine was significantly higher after formal gymnastics training. This is due to the high intensity of training performed in gymnastics and the fact that training always includes stresses in different directions. According to recent studies, this is a more appropriate training method due to the fact that it has various different forces on the bone, such as pressure and shear, which can effectively increase bone density. It is evident that gymnastic training is a more effective exercise program if it is to effectively maintain and improve the prevention of lumbar spine fractures. It has also been measured that the bone mineral content of the humerus and radius of the racket-holding hand of professional tennis players is 13% and 7.9% higher than that of the opposite side, while the bone mineral content of the opposite side is not significantly different from that of their normal counterparts. Therefore, if one wants to maintain and improve the bone mineral density of the upper extremity and prevent the vulnerability to Colles fractures, tennis is the program to choose, but with attention to simultaneous exercise on both sides.
Increasing BMD through resistance training has been reported with increasing interest in recent years. nelson conducted 52 weeks of high intensity strength training twice a week in menopausal women aged 50-70 years without any resistance training in the control group. The training method was as follows: hip extension, knee extension, spinal extension, lumbar extension, and abdominal flexion on a pneumatic resistance trainer, with each movement given a load type of 80% of the maximum load. As a result, the bone density of femoral neck and lumbar spine in the experimental group increased by 0.9% and 1.0%, respectively, while that of the control group decreased by 2.5% and 1.0%, respectively. In addition, the whole-body bone mineral content of the experimental group remained at the same level, while that of the control group decreased by 1.2%. In addition, muscle strength and balance were significantly enhanced in the experimental group, which was significantly different from the control group (P>0.01). Braith reported a 3% decrease in whole-body BMD in patients 2 months after heart transplantation due to inactivity, resulting in 9 patients returning to their preoperative BMD after 6 months of resistance training, while 8 untrained patients showed a continued trend of BMD However, the BMD of the 8 untrained patients continued to decrease. In conclusion, the effectiveness of resistance training in the prevention and treatment of osteoporosis was confirmed. Resistance exercise has the advantages of being simple, easy to perform, easy to control, and not limited by space compared to other exercise programs (running, swimming, hiking, ball games, etc.).
There are three types of resistance exercise: isometric, isotonic, and isokinetic. For patients with osteoporosis, isometric exercises are more advantageous in the treatment of patients with osteoporosis with pain, because the joints do not produce movement, thus reducing the pain caused by joint movement. In contrast, isokinetic training, especially for patients with osteoporosis specifically using isokinetic trainers, has not been reported.
4.3 Studies on the amount of exercise
4.3.1 Exercise intensity Within a certain range, the greater the exercise intensity, the greater the stress stimulation to the bone, and the more beneficial to the maintenance and improvement of bone density. Beyond a certain range, there is a risk of fatigue fractures, and the tolerance of each person’s circulatory system is limited. Therefore, before exercise must do the necessary exercise in line with the test, such as plate test, step test, power bike test. Strictly control the intensity of exercise according to the results of the test. Strictly control the intensity of exercise according to the results of existing tests. According to the existing literature, most researchers set the intensity of aerobic exercise to 60%-90% of my maximum heart rate if there are no other diseases
4.3.2 Exercise time There is no uniform standard for exercise time, but for general aerobic exercise, the exercise intensity is high and the time is short; the exercise intensity is low and the time can be slightly longer. Most researchers set the exercise time at about 30-60 minutes.
4.3.3 The frequency of exercise was mainly based on the subjective feelings of the trainees, with the degree of not feeling fatigue the next day. Generally, 3-5 days per week is appropriate. Too little exercise is not effective, while too many times will produce fatigue.
4.3.4 The phase of exercise Many scholars believe that the longer you stick to it, the better. Long-term adherence to planned and regular exercise and the establishment of good habits can not only improve physical fitness, but also have a certain effect on delaying the loss of bone mass.
5.Summary
(1) For adolescents in the growth and development period, exercise can increase the peak bone calcium. With the increase of exercise intensity and the growth of exercise history, there is a tendency for BMD values to rise. Exercise prescriptions to promote bone health in young adulthood should be done consistently. The program should be a high-intensity exercise that is appropriate for the individual.
(2) Aging causes a significant decrease in the bone mineral content of the body, but appropriate exercise can slow the bone loss that occurs with aging. Moreover, its effect increases with the increase of load within the appropriate load, but beyond a certain amount of load, the bone mineral content does not increase, nor does the bone density, and there is an inhibition of osteogenesis and causes microscopic damage to bone and an increase in local bone resorption. Based on the combination and principles of whole-body exercise and special exercises for osteoporosis-prone areas (forearm, lumbar spine, femur, lower limb, etc.), appropriate exercise programs and exercise frequency should be selected.
(3) Because the bone mineral content and bone density increased by exercise after a period of cessation of training, with the growth of age and the acceleration of the loss, bone density decreased. Therefore, long-term exercise must be maintained to prevent osteoporosis.
(4) Do not replace hormone replacement therapy at the beginning of menopause with increased exercise; the combined effect of exercise and drugs or nutrition to prevent osteoporosis is better than the effect of any single means.