I. The relationship between exercise and endocrine hormones
Exercise increases estrogen concentration in postmenopausal women, which increases bone calcium content. Testosterone and estradiol can promote protein synthesis of bone and increase the total amount of bone matrix, resulting in retention of bone salt deposits, bone thickening and epiphyseal fusion, thus promoting bone growth and development. Interleukin-1 and interleukin-6 both stimulate bone resorption, and regular exercise training can reduce the levels of these cytokines, delaying osteoclast activity and reducing bone loss.
Endogenous prostaglandin E2 (PGE2) and prostaglandin I2 (PGI2) are known to promote bone formation, and PGE2 and PGI2 secretion increases under mechanical stress of exercise. Exercise training raises testosterone and estrogen levels and promotes skeletal growth, bone cortical thickening, and increased bone density. kawata et al. administered tension stimulation to rat skull cells and saw IGF-1 and osteocalcin formation after 24 hours. There must be some coupling mechanism between this mechanical stimulation and the upregulation of local gene and cytokine expression.
There is a mechanical signal receptor in the tissue that converts mechanical signals into biochemical signals and the expression of this receptor can be upregulated by sex hormones. Zhang Peizhen et al. found that swimming at appropriate loads slowed the decrease in sex hormone levels that occurs with ageing, especially at higher loads. Shao Zhijie et al. observed the effect of long-term adherence to swimming exercise on E2 in postmenopausal women and found a significant increase in the swimming group (33.030 ± 1.35 pg/ml vs. 26.065 ± 1.52 pg/ml).
However, the dual effect of exercise on sex hormone changes should be recognized. Intense athletic training can interfere with the menstrual cycle of female athletes, leading to estrogen deficiency and consequent loss of bone inorganic salts, increasing the risk of fracture.Drikewaten studied the bone inorganic salt content of the lumbar spine and forearm in 28 female athletes using photon absorptiometry. A significant effect of weekly training (running) volume on menstruation was found. The group that ran 24.9 miles per week had normal menstruation; the group that ran 41.8 miles per week produced amenorrhea.
There was no significant difference in forearm bone inorganic salt density between the two groups of subjects, but a significant difference was seen in inorganic salt density in L1-4. Nelson et al. compared the BMD of 11 subjects who developed amenorrhea for more than 1 year with that of 17 female runners with normal menstruation (mean age 25.2 and 29.2 years; similar height, weight, and body surface area percentages, respectively). The radial inorganic salt density of the subjects in the amenorrheic group was found to be 1.099 ± 0.027 g/cm2, significantly lower than the 1.196 ± 0.025 g/cm2 in the normally menstruating group.
The study further demonstrated that the blood estradiol concentration was reduced in amenorrheic female athletes. In response to the decrease in exercise estrogen levels, Wancus et al. studied the bone mass and metabolic status of 17 female superior distance runners. The subjects were highly trained and were able to run 10,000 m in less than 3 hours. Among them, 11 had secondary amenorrhea (1-7 years) and 6 had normal menstruation. By measuring and analyzing their training intensity, body composition and endocrine levels, it was found that amenorrheic athletes were characterized by young age, low body weight, low estrogen levels, low spinal bone density and low calcium intake.
Inorganic salt density of the lumbar spine measured by CT was 182 ± 4.9 mg/ml in the normal menstruation group and only 151 ± 8 mg/ml in the amenorrheic group (20% lower) . In contrast, the non-athlete control group of women of the same age was 166±4mg/ml, which was 10% higher than the amenorrheic female athlete group. It is noteworthy that the percentage of fractures increased in the amenorrheic group of athletes, and six had a history of multiple tibial and bone fatigue fractures.
Second, the reasonable choice of exercise mode and timing
Exercise as an important means of preventing osteoporotic fractures has its mechanical characteristics, firstly, it is site-specific, that is, the bone density at the stress-bearing part of the skeleton increases significantly, and secondly, the increased bone mass will be lost due to the termination of exercise. It is obviously important to design exercise prescriptions for different age groups, for example, the purpose of exercise is to increase the peak bone mass as much as possible in adolescence in order to achieve optimal bone salt reserve. In the elderly, the main objective is to slow down the loss of bone salts.
1, the purpose of exercise to prevent osteoporosis:
(1) exercise through muscle contraction generated tension and mechanical stress on the bone, promote bone formation and prevent bone loss.
(2) exercise training to enhance the strength of the back muscles, help support the spine and prevent vertebral wedge changes or kyphosis deformity.
(3) Exercise improves the flexibility and balance of the body and prevents fractures caused by falls.
(4) Proper regular exercise can reduce the symptoms of back pain.
2.Exercise for osteoporosis:
(1) Aerobic endurance exercise Aerobic exercise methods such as jogging, brisk walking, cycling and climbing steps can directly play a role in stimulating bone formation and inhibiting bone resorption.
② Muscle strength training Muscle strength training can prevent the decrease of muscle strength caused by ageing and help prevent and treat osteoporosis. Plyometric exercises include isotonic exercises represented by barbells and dumbbells, isometric exercises that force against resistance without movement, and isokinetic exercises that require special equipment. The above-mentioned exercises increase local muscle endurance and there will be a corresponding growth of local muscles, and they also improve the coordination function of the body.
Patients with osteoporosis are recommended to perform a comprehensive exercise program based on lighter weight-bearing, which will strengthen the muscle groups attached to the bones. The patient does activities to change position, which can influence the load exerted by the curvature of the bone surface, which is related to the reconstruction of the bone, so that the exercise increases the convex surface area, stimulates osteoblast activity and enhances the ability of the bone to withstand stress. These exercises, of course, are based on the potential ability of the individual and should be started with a minimal load and increased gradually to give the patient enough time to adapt.
Progressive resistance exercise can achieve enhanced bone health and improved function, but only for patients with osteoporosis without fractures. Progressive resistance exercise has a greater effect on building muscle strength and increasing bone density than endurance exercise produces. Resistance exercise of the hip joint increases bone density of the greater trochanter, but has little effect on the femoral neck.
③ Balance and flexibility training is an important form of exercise for fall prevention, such as gymnastics, dance, and tai chi. The literature reports that performing tai chi exercises can reduce the incidence of falls and prevent hip fractures in particular. Patients with very low bone density and multiple fractures need to have muscle protection for the bones and should have exercise training to enhance muscle strength and improve balance and flexibility, but avoid activities with spinal flexion.
For patients with significantly reduced bone density and with muscle weakness and balance disorders, exercise training can strengthen coordination and balance, resulting in increased bone density and muscle strength, which can prevent falls. Flexibility training can maintain the proper range of motion of the joints and can maintain the normal function of the musculoskeleton. Stretching exercises are divided into dynamic and static stretching. Dynamic stretching is the use of inertia flexion and extension of joints, and static stretching exercises should be done before exercise.
Static stretching exercises of medium intensity can reduce the tension of muscle nerves, joint flexion and extension to a certain position to maintain 10-30 seconds, the degree of stretching to not cause pain as the limit. Static stretching exercises occur less trauma, suitable for the middle-aged and elderly joint stretching exercises, can be carried out three times a week.
3, osteoporosis exercise intensity and duration of the general principles: exercise quantification is the key to the development of osteoporosis exercise prescription. For individual differences in exercise capacity, bone density and the presence of fractures to develop exercise therapy programs. The intensity of exercise to perform aerobic endurance exercise can be used as the following indicators (1) heart rate: as an indicator of the intensity of exercise during training, called the target heart rate or target heart rate. The target heart rate of exercise is calculated based on the individual’s maximum heart rate, such as the maximum heart rate multiplied by a percentage to obtain the target heart rate of exercise.
(2) Conscious exercise intensity RPE grading: RPE can be used independently or in combination with heart rate to assess the exercise intensity of aerobic endurance training. 12-13 on the RPE grading scale is equivalent to 60% of the maximum heart rate, 16 is equivalent to 90% of the maximum heart rate. Patients with osteoporosis without fractures should be trained in the range of 12-13. The intensity of exercise varies according to the individual and the degree of osteoporosis. Exercise intensity should be gradually increased to make the bone strong. The exercise load should be within the range of mechanical stress that the bone can withstand. Low-level exercise has a role in maintaining bone density, and high-level exercise can strengthen bone mass to adapt to new environments.
The minimum amount of the appropriate type of exercise has the effect of stimulating osteoblasts. Exercise duration: There should be preparatory activities and finishing exercises (10-15 minutes) during each exercise training, and the exercise duration is generally 20-30 minutes. Patients with osteoporosis should not exercise for a short period of time with high intensity, and should exercise for a longer period of time with low intensity.
In the first week of exercise, low and moderate intensity exercise should be performed for 20-30 minutes, and the exercise duration can be gradually increased from 20 minutes when normal exercise response occurs after 2-4 weeks of exercise and there are no complications. Intermittent exercise may also be performed in patients with severe osteoporosis. The frequency of exercise is usually 3 times a week.
4, the choice of exercise for different age groups:
(1) The choice of exercise methods for adolescents During adolescence, the bones have not been fully ossified, and there is cartilage and epiphyseal cartilage between the epiphysis and the backbone of the long bones, and during childhood and adolescence, epiphyseal cartilage grows rapidly, especially in the extremities, and during this period, the pressure on the bone is small and easily deformed, therefore, the content of physical exercise should be based on speed and burst force items, less weight bearing, short exercise time per group, and long intervals. The intervals should be long, and the intensity and amount of exercise should be moderate.
When Yuxiang He et al. observed the effect of exercise on BMD in adolescents, 46 general elementary school students aged 8-9 years were divided into 3 groups: 13 in group 1, who insisted on 1 hour of track and field training every day, as the large-exercise group, and 17 in group 2, who insisted on 20 minutes of track and field training every day, as the small-exercise control group and 16 in the non-exercise group.
The bone density of the orthostatic L2-4 , left femoral neck, greater trochanter, Ward’s triangle and radial ulna of the non-dominant arm were measured in the athletic group before and after 4 months of training, and the changes in bone density values were better in the large-exercise group than in the small-exercise and non-exercise groups after 4 months of athletic training, and no differences were seen between the small-exercise and control groups. Therefore, to increase BMD, improve peak bone mass and prevent osteoporosis through physical exercise, youths must achieve a certain exercise intensity and sufficient exercise time to achieve good results.
(2) The choice of exercise methods for young people Young people basically stop the ossification process by the age of 25, their bone stress capacity is greatly enhanced, and their general athletic ability is also very strong, this period of training should use more burst force and a certain amount of absolute strength and moderate amount of endurance exercises, with more direct exercise to stimulate the bone to produce more obvious therapeutic effect, such as multiple 50-100 meters of sprinting, push-ups and weighted squats, etc. Exercise exercises can prevent and control osteoporosis of the long bones of the limbs, proximal and distal, and the spine.
(3) Selection of exercise methods for middle-aged and elderly people The physiological characteristics and exercise ability of middle-aged and elderly people determine that the selection of exercise methods should be different from those of patients in other age groups. Gu Liyan et al. conducted a study to compare the general elderly exercise group and aerobic exercise (long-distance running) elderly group. The results showed that geriatric osteoporosis is an inevitable trend, an irreversible process of change with age, but the decline in the aerobic exercise group was lower than that in the general group, indicating a more positive effect of aerobic exercise on maintaining the mineral content of living bone and delaying the appearance of geriatric osteoporosis.
This result confirms that gravity has a favorable effect on bone formation, as long-distance running training increases the stimulating effect of body weight on bone. Yang Baozhu et al. divided 145 cases of retired people with basic health, including 90 men and 55 women aged 50-70 years old, who participated in sports including gateball, billiards, table tennis, taijiquan (sword), walking, dancing, and geriatric aerobics, into small activity group, medium activity group, and large activity group according to the accumulated time of participation per month.
The small activity group was 0.5-1 hour/day, the medium activity group was 2 hours/day, and the cumulative time was 1 year; the large activity group was 3-4 hours/day, and the cumulative time was 2 years. As a result, the incidence of osteoporosis in the small and medium activity groups was 37.5% (33/88) and 75% (21/28), respectively, while no osteoporosis occurred in the high activity group. This result proves that aerobic exercise can effectively prevent and treat osteoporosis in middle-aged and elderly people, and on the other hand, it proves that middle-aged and elderly people should increase the amount of exercise within their capacity in order to achieve better prevention and treatment effects.