Everett L. Smith

Physical activity and calcium modalities for bone mineral increase in aged women

This study tested the hypothesis that physical activity and/or supplemental calcium (0.75 g/day) and vitamin D (400 IU) would effectively slow bone loss, and /or increase bone mineral content (BMC) in aged females (X = 81) over three years. In vivo BMC and width of the radius was determined by photon absorptiometry at two sites. Four groups were formed: a control, a drug, a physical activity, and a physical activity plus drug. A single tailed t-test was used to compared the slope of the linear regression of 10 data points collected on each subject. The BMC of the control group declined 3.29%, while the physical activity group and drug group demonstrated a 2.29% (p less than .05) increase and a 1.58% (p less than .07) increase respectively, during the study.

Deterring bone loss by exercise intervention in premenopausal and postmenopausal women

SummaryThis study investigated the efficacy of 4 years of exercise intervention in deterring bone loss in middle-aged women, and is a correction and extension of previously published data. Sixty-two control subjects (mean age 50.8) and 80 exercise subjects (mean age 50.1) completed a 4-year study. Subjects exercised three times a week, 45 minutes per session. Bilateral radius, ulna, and humerus bone mineral content (BMC) and width (W) were measured on each subject 11 times over the 4-year period. The two groups did not differ initially in age, height, or weight, but the control group had a greater maximum VO2 (ml/kg/min) than the exercise group. Slopes and intercepts of the bone variables vs. time were determined for each subject, and these values were used for between-group comparisons of loss. The control group BMC and BMC/W declined significantly in all three bones in both arms. The exercise group rate of decline was significantly less than that of the control group for 12 of the 18 bone variables. The greatest effect of the exercise intervention was on the ulna and radius. Exercise subjects lost significantly less than control subjects in left and right ulna and radius BMC and BMC/W, and left ulna and radius W. Lesser differences between groups were observed in the humerus. BMC and W loss rates of the left humerus were reduced in the exercise group, with no difference between exercise and control subjects in the other humerus variables. To determine if menopausal status influenced the response to exercise, we analyzed the difference between groups for premenopausal and postmenopausal subjects separately. Regardless of menopausal status, exercise subjects had lower bone loss rates than control subjects. In both premenopausal and postmenopausal subjects, exercise reduced bone loss significantly for 10 of the 18 bone variables. It can be concluded that physical activity significantly reduces bone loss in the arms of middle-aged women.

Physical activity effects on bone metabolism.

SummaryThe incidence of osteoporotic fractures rises exponentially with age and is increasing faster than the demographic increase in the aging population. Physical activity has great potential to reduce the risk for osteoporotic fractures. Three independent but interactive factors contribute to the risk of fractures: bone strength, the risk of falling, and the effectiveness of neuromuscular response that protects the skeleton from injury. Exercise can reduce fracture risk not only by preventing bone loss, but by decreasing the risk of falling and the force of impact by improving strength, flexibility, balance, and reaction time. Extreme inactivity causes rapid bone loss of up to 40%, while athletic activity results in bone hypertrophy of up to 40%. Exercise intervention programs have reduced bone loss or increased bone mass in both men and women of various ages and initial bone status. These benefits have been shown for arm bone mineral content, total body calcium, spine, calcium bone index, tibia, and calcaneus. In both middle-aged and elderly women, physical activity intervention reduced bone loss or increased bone mass. The mechanisms for maintenance of skeletal integrity rely on a cellular response to hormonal and mechanical load stimuli. Studies in animal models show that training affects cellular activity. In osteoporotics, cellular erosion is increased and mineral apposition rate (MAR) decreased compared with normal age-matched controls. In contrast to this, sows trained on a treadmill 20 min per day for 20 weeks had greater active periosteal surface, periosteal MAR, and osteonal MAR than untrained sows.

Muscular strength and bone density with weight training in middle-aged women

Previous research has demonstrated positive correlations between bone mass and both physical activity and muscular strength. There is a paucity of information describing the specific type of exercise which most benefits the human skeleton. The effects of a 1 yr weight training program on 18 middle-aged women participating in an endurance dance program (E + W) compared with 17 other women in the endurance dance program only (E) and with 19 sedentary controls (C) were studied by measuring muscular strength and bone mineral density (BMD). Eighteen women in the E + W group demonstrated increases in all strength measurements, whereas the E and C groups either had smaller increases or had declined. A significant group x test interaction term, indicating that groups responded differently over time, was observed for nondominant isokinetic elbow flexion measured through the range of motion at a constant velocity of 60 degrees.s-1 (P less than 0.05), nondominant isokinetic elbow extension at 180 degrees.s-1 (P less than 0.01), and nondominant isokinetic elbow flexion at 180 degrees.s-1 (P less than 0.05). BMD did not change significantly except that a significant group x test interaction term appeared for the radius ultradistal site (P less than 0.01). BMD of the humerus and femoral Wards triangle increased nonsignificantly in both E and E + W over the year. This weight training program increased muscular strength but did not increase measured bone mass.

Total body and regional bone mineral by dual-photon absorptiometry in metabolic bone disease

SummaryDual-photon absorptiometry (153Gd) was used to measure bone mineral of the total body and major anatomical areas. Patients with osteoporosis (♂=11, ♀=18) and with renal osteodystrophy (n=17) were significantly below (20%) normal females (n=72) and males (n=13) at most sites. In the osteoporotic patients, but not the renal patients, there was preferential osteopenia of the spine. Bone loss in all anatomical areas became evident after the menopause with an annual loss rate of about 0.7%.

Bone involution decrease in exercising middle-aged women.

SummaryPhysical activity is an important stimulus in the prevention of bone involution. Bilateral bone mineral mass and width of the radius, ulna, and humerus were measured by single photon absorptiometry on 200 women between the ages of 35 and 65 over a 3–4 year period. Two groups were formed: 80 in a control group and 120 in a physical activity group exercising 45 min/day, 3 days/week. The control and physical activity groups were similar in age, height, weight, and level of physical fitness at the beginning of the study. The control group lost bone mineral mass at a rate similar to that of the general population. The left radius bone mineral declined 2.44% per year. Similar rates of decline were observed in the other bones measured. The physical activity group increased in fitness by 13% in the first year of the study. The bone mineral mass of the exercise group declined the first year and then increased; thereby the bone mineral data for the exercise group was analyzed in two sets. During the first year of the program, a decline of 3.77% in bone mineral mass of the left radius, a significantly greater loss than that of the control group, was observed. Decline rates were similar in the other bones measured. In the second and third years, bone mineral mass of the left radius increased by 1.39% per year, and the rate of change was significantly different from that of the control group. There were similar increases in the other bones measured. The data from this study support the importance of physical activity in the prevention of bone mineral loss in the aging female.

Dose-response relationship between physical loading and mechanical competence of bone

A dose-response relationship between mechanical loading and bone can be inferred by the fact that bone response is proportional to the applied load in cell and organ culture and in animal models where a known load at a given magnitude and frequency is applied. Proportional responses have been observed in second messengers, growth factors, bone matrix, and bone strength. In the human model, however, the determination of a dose-response relationship is hindered by the lack of appropriate technology to directly evaluate the mechanical load and the skeletal competence. In vitro loading of bone does not duplicate the in vivo physiologic conditions, in particular the neuromuscular responses to the loads applied to the skeleton. While animal studies aid in determining the mechanisms of bone response to mechanical loading and dietary interactions, they do not obviate the need for human clinical trials to evaluate the effects of physical activity on both skeletal competence and fall prevention. The literature reviewed shows that physical activity increases the competence of the skeleton to resist fracture by the maintenance and improvement of bone mineral density (BMD) and neuromuscular competency, thus reducing skeletal fragility, pre-disposition to falls, and fall impact.

Physical Activity Prescription for the Older Adult

In brief: Disuse accounts for about half of the functional decline that occurs between ages 30 and 70, and aging causes the other half. This article describes how to reverse the decline caused by disuse with a physical activity program tailored to the needs of older adults. The authors give safety tips for exercise testing with a bicycle ergometer and treadmill, as well as a step test that can be performed while sitting. They also present simple equations for computing percent of maximum heart rate, maximum met level, calories used during exercise, and duration of exercise at a particular intensity. Specific examples of how to use the equations are included, along with a list of activities and their met levels.

Winning the Battle Against Childhood Physical Inactivity: The Key to Bone Strength?†

IN THIS ISSUE, Gunter et al. highlight the convergence of two factors that greatly promote bone health—the critical period of bone accrual during childhood and the importance of bone loading through specific physical activity. Bailey and McCulloch and others first alluded to the possibility that adult osteoporosis had its antecedents in childhood. In 2008, the verdict is in—well-designed childhood physical activity programs are likely critical for preventing osteoporosis in mature adults. Advances in novel imaging technology and analysis methods suggest that the early DXA-based bone and physical activity studies may have underestimated the importance of developing a greater peak bone mass in childhood through targeted physical activity, which will benefit skeletal integrity for life.

Osteocyte Apoptosis and Osteoclast Presence in Chicken Radii 0–4 Days Following Osteotomy

Osteocyte apoptosis caused by load-induced microdamage is followed by osteoclastic bone remodeling, and a causal link between apoptosis and repair has been suggested. The objectives of the present study were to use a chick model to examine the incidence of osteocyte apoptosis and the presence of osteoclasts during the first 96 hours following an osteotomy, prior to extensive callus mineralization. Osteotomies were performed on the right radii of 24 chicks at 23–24 days of age. The left radii served as controls. Radii were collected and processed at six time points following surgery (0, 12, 24, 48, 72, and 96 hours). Decalcified bone tissue sections were stained either for apoptosis using a modified TUNEL procedure or for tartrate-resistant acid phosphatase to identify osteoclasts in the intracortical and periosteal envelopes. The percentage of apoptotic osteocytes, as well as osteoclast counts (n/mm or n/mm2) were quantified in four regions (0–1, 1–2, 2–4, and 4–8 mm from the site of the osteotomy; regions 1–4, respectively) in the osteotomized radii and in the same measured areas in the control radii. Data for osteocyte apoptosis and osteoclasts in the control limb were subtracted from the osteotomized limb data to identify differences due to surgical influence. The incidence of osteocyte apoptosis was significantly higher at 12, 24, 48, and 72 hours versus 0 hours following osteotomy, and the response was highest in region 1; however, there was no interaction between time and region. Intracortical osteoclast counts (n/mm2) were elevated after 48 hours, and the response was similar in all regions. The data demonstrate that osteocyte apoptosis occurs within 24 hours in response to an osteotomy and temporally precedes an increase in osteoclast presence. Hence, osteocyte apoptosis may play a role in signaling during the bone healing process.