The effects of exercise on bone. Basic concepts and implications for the prevention of fractures.

Osteogenic dynamic loads delivered to the skeleton during exercise prevent aging-associated bone fragility. Moreover, because of its pleiotropic favourable effects on health, exercise improves quality of life, and specific types of exercise increase muscle strength, a known predictor of bone strength, and coordination and balance, and so reduce the risk of fallrelated fractures. Exercise should definitely be the mainstay of the prevention and treatment of osteoporosis; often however, physicians don't have enough know-how for evidencebased prescription of exercise. Moreover, the lack of facilities for safe implementation of the exercise programs compound the problem. Scientific societies and health authorities should invest in patient and physicians education about exercise and in promoting facilities (Gyms) devoted to training of persons with, or at risk of, metabolic diseases (osteoporosis, obesity, diabetes), like Metagym in Florence, Italy.

Structural adaptations to bone loss in aging men and women.

INTRODUCTION: Bone apposition on the subperiosteal surface and bone loss from the endocortical surface during aging establish the external diameter, total cross-sectional area (tCSA), cortical thickness (Ct.Th) and the distance the cortex is placed from the neutral axis of a long bone, all determinants of bone strength. We tested the hypothesis that sex-related differences in these processes produces a sexual dimorphism in tibial fragility. METHODS: The above traits were assessed in 688 women and 561 men (20-102 years old) using peripheral QCT. RESULTS: Total and medullary areas were greater in young adult men than young adult women. As age advanced, in men, tCSA area increased by 0.79 SD, and medullary area increased by 0.54 SD so that cortical area, cortical thickness and minimum and maximum moments of inertia (Imin and Imax) were similar at all ages. In women, tCSA increased by 0.2 SD, while medullary area increased by 2.6 SD so that cortical area and thickness and the moments of inertia diminished. Cortical apparent volumetric bone mineral density (vBMD) declined more in women (by 3.1 SD) than men (by 0.5 SD). In both sexes, the lower the cortical apparent vBMD, the higher the tCSA (women R2 = 0.13, men R2 = 0.16, both P < 0.0001), whereas the lower the Ct.Th, the lower the tCSA (women R2 = 0.30, men R2 = 0.32, both P < 0.0001). CONCLUSIONS: Bone loss reduces cortical thickness and increases intracortical porosity. These changes tend to be compensated for by periosteal apposition in both sexes but more greatly in men than in women, perhaps because this mechanism may be ineffective when cortical thinning is severe.

Urinary calcium is a determinant of bone mineral density in elderly men participating in the InCHIANTI study.

BACKGROUND: It is generally acknowledged that calcium excretion is a determinant of bone mineral density. Since data confirming this hypothesis are not conclusive, the present study evaluates the relationship between calcium excretion and volumetric bone mineral density (vBMD) in a sample of general population mostly composed of elderly subjects. METHODS: This relationship was studied in 595 subjects in good health (M/F 302/293), selected from the InCHIANTI population, an epidemiologic survey on aging in Tuscany (Italy). Of these subjects, 432 (72.6%) were 65 years old or older. Trabecular and cortical apparent vBMDs were measured by peripheral quantitative computed tomography at right tibia and standardized to age and body mass index (BMI) in each gender (z-score). RESULTS: Men in the highest tertile of calcium excretion had significantly lower trabecular vBMD, and were more likely to have a trabecular z-score of -1 or less. These results were confirmed in men older than 64 years, but not in women and younger men. Sodium excretion and 25-hydroxycolecalciferol (25(OH)D) were greater in men and women in the highest tertile. No differences among tertiles were observed for cortical vBMD, circulating levels of interleukin-1beta and interleukin-6, and intake of principal nutrients and calcium. The lower levels of vBMD z-score were confirmed in men in the highest tertile of calcium excretion, standardized to creatinine clearance, sodium excretion, plasma calcium, and logarithm of circulating 25(OH)D, and resulted to be associated with calcium excretion at multiple regression analysis in men. CONCLUSION: High calcium excretion is associated with a decreased trabecular BMD in elderly men and may predispose men to trabecular bone loss.

Is muscle power output a key factor in the age-related decline in physical performance? A comparison of muscle cross section, chair-rising test and jumping power.

Ageing compromises locomotor capacity and is associated with an increased risk of falls. Several lines of evidence indicate that both changes in muscle mass and performance are causative. Most studies, however, do not discern between effects of ageing, sedentarism and comorbidity. The present study compares the age effects in muscle cross section, force and power in physically competent self-selected subjects of different age groups. A total of 169 women and 89 men between 18 and 88 years, without any disease, impairment or medication affecting the musculoskeletal system were enrolled in this study. Calf muscle cross-sectional area was assessed by computed tomography. Muscle force and power were assessed by jumping mechanography. No significant correlation between muscle cross section and age was found in the men. A weak correlation in the women disappeared after correction for height. Close correlations with age, however, were found for peak force and peak power. Correction for muscle cross section or body weight further increased these correlation coefficients, particularly for peak power specific to body weight (r = 0.81 in women and r = 0.86 in men). The non-sedentarian population investigated here depicted a reduction of >50% between the age of 20 and 80 without a reduction in muscle cross section. This suggests a crucial role for muscular power in the ageing process. Possibly, the jumping mechanography as a measurement of anti-gravitational power output is a promising extension of the chair-rising test, known to be predictive for immobilization and the risk of falls.

High-frequency vibration training increases muscle power in postmenopausal women.

OBJECTIVE: To test whether training on a high-frequency (28Hz) vibrating platform improves muscle power and bone characteristics in postmenopausal women. DESIGN: Randomized controlled trial with 6-month follow-up. SETTING: Outpatient clinic in a general hospital in Italy. PARTICIPANTS: Twenty-nine postmenopausal women (intervention group, n=14; matched controls, n=15). INTERVENTION: Participants stood on a ground-based oscillating platform for three 2-minute sessions for a total of 6 minutes per training session, twice weekly for 6 months. The controls did not receive any training. Both groups were evaluated at baseline and after 6 months. MAIN OUTCOME MEASURES: Muscle power, calculated from ground reaction forces produced by landing after jumping as high as possible on a forceplate, cortical bone density, and biomarkers of bone turnover. RESULTS: Over 6 months, muscle power improved by about 5% in women who received the intervention, and it remained unchanged in controls (P=.004). Muscle force remained stable in both the intervention and control groups. No significant changes were observed in bone characteristics. CONCLUSION: Reflex muscular contractions induced by vibration training improve muscle power in postmenopausal women.

Age-associated changes in skeletal muscles and their effect on mobility: an operational diagnosis of sarcopenia.

Sarcopenia, the reduction of muscle mass and strength that occurs with aging, is widely considered one of the major causes of disability in older persons. Surprisingly, criteria that may help a clinician to identify persons with impaired muscle function are still lacking. Using data from a large representative sample of the general population, we examined how muscle function and calf muscle area change with aging and affect mobility in men and women free of neurological conditions. We tested several putative indicators of sarcopenia, including knee extension isometric torque, handgrip, lower extremity muscle power, and calf muscle area. For each indicator, sarcopenia was considered to be present when the measure was >2 SDs below the mean. For all four measures, the prevalence of sarcopenia increased with age, both in men and women. The age-associated gradient in prevalence was maximum for muscle power and minimum for calf-muscle area. However, lower extremity muscle power was no better than knee-extension torque or handgrip in the early identification of poor mobility, defined either as walking speed <0.8 m/s or inability to walk at least 1 km without difficulty and without developing symptoms. Optimal cutoff values that can be used in the clinical practice to identify older persons with poor mobility were developed. The findings of the study lay the basis for a cost-effective, clinical marker of sarcopenia based on a measure of isometric handgrip strength. Our findings should be verified in a longitudinal study.

Changes in anthropometric measures in men and women across the life-span: findings from the InCHIANTI study.

OBJECTIVES: To describe the age distribution of anthropometric parameters in a population-based sample of older persons. METHODS: Cross-sectional survey of a population-based sample of persons over a wide age-range living in the Chianti area, Italy, between 1998 to 2000. Total cohort: 1453 men and women, of whom 424 younger than 65 and 1029 aged 65 years or older. Participation rate: 69.4% in < 65 yrs and 91.6% in > or = 65 yrs. Analytical cohort: anthropometric measures were available for 1266 subjects. RESULTS: Height and weight declined with increasing age in both sexes. In men, Body mass index (BMI) increased with age up to age 45-54 and then it declined. In women, it reached its maximum at age 65-74 and remained higher than in men in each corresponding age group above 65 years of age. Waist-to-hip ratio (WHR) progressively increased in men up to age 55-64 and then slightly declined. In women WHR steadily increased over the entire age range. CONCLUSIONS: Height and weight decline with age, regardless to differences in body size attributable to secular trend. In both sexes, important fat redistribution occurs between 45 and 54 years and in older women the increase in WHR mostly reflects a reduction of fat deposits in the hips. This information may be relevant for a correct interpretation of changes in WHR in older persons. However, these findings were obtained in a cross-sectional study and should be verified in a longitudinal perspective.