Physical fitness effect on bone mass is mediated by the independent association between lean mass and bone mass through adolescence: a cross-sectional study

We studied 278 adolescents (169 females) aged 13.0–18.5 years to elucidate whether an independent effect of physical fitness and lean mass in the differences between male and female bones can be detected. Lean and fat masses and bone mineral content (BMC) were measured with DXA. Physical fitness was evaluated with six different tests included in the EUROFIT test battery (flexibility, isometric, dynamic and endurance strength, speed, and cardiovascular fitness). To test the independent relationship between physical fitness and bone mass, multiple regression analysis was applied, including lean mass, age, and Tanner development as covariates. The males had a 43% lower fat mass and 40% and 16% higher lean mass and total BMC compared with the females (all P < 0.05). After adjustment for differences in body size and lean mass, the females exhibited a 7.4% higher BMC than the males (P < 0.05). The multiple regression analysis showed that lean mass had an independent relationship with bone mass (P < 0.001), explaining 67% of the total variance in whole-body BMC. In males, change in R ² was 0.658 for hand grip and 0.035–0.151 for the rest of physical fitness-related variables; but 0.019–0.042 in females (all P–0.001); however, the independent relationships between physical fitness and bone disappeared after controlling for lean mass. In conclusion, it is likely the differences between male and female in bone mass could be explained by differences in lean mass and physical fitness.     

Growth and Bone Mineral Accretion During Puberty in Chinese Girls: A Five‐Year Longitudinal Study

There are few longitudinal data on bone development during puberty in children with low calcium intake. This 5‐yr longitudinal study showed that, in Chinese girls, the mean apparent calcium retention efficiency during puberty was 40.9%, PHV occurred at 3–0 yr before menarche, and peak bone mineral accretion occurred 1 yr later than PHV. Chinese girls have high calcium retention efficiency during puberty. Introduction: There are few longitudinal data on bone development during puberty in children with low dietary calcium intake. The aim of this study was to examine the rate of growth and bone mineral accretion and study the predictors of total body BMC during puberty in a 5‐yr longitudinal study with Chinese girls. Materials and Methods: Ninety‐two girls, 9.5–10.5 yr of age at baseline, from the unsupplemented control group of a school milk intervention trial were included in this analysis. Data on anthropometric measurements, total body BMC as assessed by DXA, and calcium intake as assessed by a 3‐day food record were obtained at baseline and 1, 2, 4, and 5 yr. Results: The mean age of menarche was 12.1 ± 1.0 yr. The mean annual rate of bone mineral accretion was 197.4 g/yr during the follow‐up period, representing a calcium accretion rate of 162.3 mg/d. This calcium retention rate and the average dietary calcium intake of 444.1 mg/d gave an apparent calcium retention efficiency of 40.9%. Peak height velocity (PHV) occurred at 3–0 yr before menarche. Peak bone mineral accretion occurred 1 yr later than PHV. There was a decrease in size‐corrected BMD in the year before menarche. In the linear mixed‐effects model analysis containing body size and lifestyle factors, we found that height, body weight, and calcium intake were significant independent predictors of total body BMC. Conclusions: Chinese girls with low habitual dietary calcium intake have high calcium retention efficiency during puberty. Because calcium intake is a significant predictor of total body BMC, increasing dietary calcium intake may have beneficial effects on bone mineral accretion in these girls.     

Long‐term survival after kidney transplantation in an HIV‐positive patient

Abstract: Only a decade ago, human immunodeficiency virus (HIV)‐seropositivity was considered an absolute contraindication for organ transplantation. With the currently available experience, it is no longer justified to deny HIV‐positive patients access to transplantation. To the best of our knowledge, we here present the longest surviving HIV‐positive patient after renal transplantation. The follow‐up period after renal transplantation in this HIV‐positive female is now 13 yr and she is in good general condition with excellent renal function. Throughout her post‐transplant follow‐up, we encountered a number of problems that are illustrative of the HIV‐positive patient.     

Long‐term effects of intermittent androgen suppression on testosterone recovery and bone mineral density: results of a 33‐month observational study

OBJECTIVE

To investigate changes in bone mineral density (BMD) and osteoporosis, over 3 years of intermittent androgen‐suppression therapy (IAST).

PATIENTS AND METHODS

This was a Phase II individual cohort study of 72 patients with prostate cancer without metastatic bone disease, enrolled between 1999 and 2002. Patients had 9 months flutamide (250 mg, three times daily) and leuprolide (22.5 mg, 3‐monthly depot) after which, patients ceased therapy providing that their PSA levels were <4 ng/mL. AST re‐commenced when the PSA level exceeded the pretreatment level or was >20 ng/mL. BMD for hip and spine was the primary endpoint; assessed at baseline; completion of initial treatment period; and at 1 and 2 years after initial treatment (POST period).

RESULTS

Osteoporosis increased from 7% at baseline to 10% at 3 years. The BMD declined after 9 months treatment, at ?1.9% and ?3.3% at hip and spine, respectively (P < 0.001). Subsequent BMD decline in the POST period was attenuated; at 1 years and 2 years later, hip ?0.6% (not significant), and ?0.8% (P < 0.014), and spine +1.0% and +0.2% (not significant). The BMD change in those remaining ‘off’ therapy for 2 years (n = 20) was strongly associated with the level of testosterone recovery; a peak testosterone level of <5 nmol/L associated with a greater then normal physiological loss. Testosterone recovery was less likely in older men.

CONCLUSION

The attenuation of spine and hip BMD decline after 3‐year IAST compared with those reported for continuous AST appears to be due to testosterone driven BMD recovery in the POST period. Failure of testosterone recovery was associated with worse final BMD. By reducing the potential risk for adverse bone complications, intermittent therapy may become an important consideration when the therapeutic ratio is narrow.     

Long‐term outcome of pediatric renal transplantation: a single center experience

Abe T, Ichimaru N, Kakuta Y, Okumi M, Imamura R, Isaka Y, Takahara S, Kokado Y, Okuyama A. Long‐term outcome of pediatric renal transplantation: a single center experience.
Clin Transplant 2011: 25: 388–394. © 2010 John Wiley & Sons A/S. Abstract: Renal transplantation is the optimal treatment for pediatric end‐stage renal disease. We examined 51 children <20 yr old who underwent a total of 52 living‐donor renal transplantations at Osaka University Hospital between 1972 and 2004. The mean age at transplantation was 13.7 (3–19 yr). The mean duration of follow‐up was 16.5 yr. The five‐, 10‐, and 20‐yr patient survival rates following renal transplantation were 94%, 90%, and 87%, respectively. The five‐, 10‐, and 20‐yr graft survival rates were 76%, 65%, and 48%, respectively. A double‐drug regimen was used before 1987; this was replaced by a triple‐drug regimen including a calcineurin inhibitor in 1988. The five‐, 10‐, and 20‐yr graft survival rates after 1988 (89%, 80%, and 60%, respectively) were higher than those before 1987. Growth was examined among patients <15 yr old at the time of surgery, and height standard deviation (SD) scores (Z‐scores) were analyzed in 14 patients who displayed favorable renal function after transplantation. At the time of transplantation, mean SD score (SDS) was ?2.39, and mean final adult SDS was ?1.79. Rates of patient and graft survival after renal transplantation were mostly favorable. Future goals must include overcoming chronic rejection and establishing a steroid discontinuation protocol to improve growth.     

Adverse interaction of low‐calcium diet and low 25(OH)D levels on lumbar spine mineralization in late‐pubertal girls

No consensus has been reached on the serum 25‐hydroxyvitamin D [25(OH)D] levels required to ensure optimal bone health around menarche. We searched for a possible interaction of 25(OH)D levels and calcium intake on lumbar spine mineralization and on biologic features of bone metabolism in healthy late‐pubertal girls. Lumbar spine parameters (ie, area, mineral content, and density) and calcium intake were evaluated in 211 healthy white adolescent girls at pubertal stages IV–V (11 to 16.9 years), together with biologic markers of calcium and bone metabolism and with International External Quality Assessment Scheme for Vitamin D Metabolite (DEQAS)–validated serum 25(OH)D levels. A high prevalence of 25(OH)D levels ≤ 30 nmol/L (41%), ≤40 nmol/L (61%), and ≤50 nmol/L (70%) was found during winter–spring. Parathyroid hormone (PTH) levels were inversely associated with 25(OH)D levels (p = .0021). In contrast, lumbar spine mineral content and density were not associated with 25(OH)D, excepted when calcium intake was below 600 mg/day (p = .0081). Girls with such low calcium intake and 25(OH)D levels of 40 nmol/L or less (9% of the cohort) had a 0.4 to 0.7 SD lower mean areal bone mineral density Z‐score than girls with higher calcium intake and/or higher 25(OH)D status. The adverse association between lumbar spine mineralization and combined calcium deficiency–low 25(OH)D levels remained significant in the 91 girls who could be followed over 4 years after their initial evaluation. We conclude that low 25(OH)D levels (≤40 nmol/L) are observed frequently during winter–spring in late‐pubertal European girls, which may exacerbate the negative impact of calcium deficiency on lumbar spine mineralization. © 2010 American Society for Bone and Mineral Research.     

Gain in mass density of bone following strenuous physical activity

A group of 223 military recruits aged 18-21 years underwent strenuous physical training for a period of 14 weeks. The absolute bone density of the distal tibia in both lower limbs was measured before the training period and at its end. The density was determined by the Compton scattering technique, which has been developed in our laboratory; this method provides the bone mass of all bone constituents per unit volume. The distribution curve of the bone density in both tibiae shifted to higher values at the end of the training period. The mean bone density in the right and left tibia increased significantly by 7.5%. This study indicates that following an intensive physical exercise regime, a significant increase in the mass density of bone can be obtained in young adults within a short period.     

Relationship between vitamin D status, body composition and physical exercise of adolescent girls in Beijing

Summary  Little is known about the prevalence of actual vitamin D deficiency in healthy school-aged adolescents, particularly in China. The aim of this study was to examine the prevalence of hypovitaminosis D and to identify whether there was any association between vitamin D status, body composition and physical exercise in 323 Chinese adolescent girls in Beijing, China (40°N). Introduction  It is well recognized that persistent severe vitamin D deficiency is associated with the bone abnormalities of rickets and osteomalacia. However, there is now evidence suggesting that low vitamin D status, not previously considered to be a state of deficiency is associated with secondary hyperparathyroidism, increased bone remodelling and other clinical signs thought only to be found in severe vitamin D deficiency. Hypovitaminosis D in healthy children and adolescents has been reported frequently in many countries, especially in winter. Methods  We performed a cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter. Mean age of the subjects was 15.0 (±0.4) years. About 32.8%, 68.4% and 89.2% of the subjects were at risk of vitamin D deficiency when defined as plasma concentrations of 25(OH)D of 25, 37.5 or 50 nmol/L, respectively. Results  This cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter showed that hypovitaminosis D was common in these subjects. In addition, body mass index, milk intake, participation in organized sports and total physical activity were all significant independent determinants of vitamin D status. An inverse association was found between plasma 25(OH)D and intact-parathyroid hormone (iPTH) concentration. Body mass index (BMI), milk intake, participation in organized sports and total physical activity all emerged as major independent determinants of vitamin D status as assessed by plasma 25(OH)D concentration. Vitamin D status was positively associated with lean body mass (LBM), but there was no association with the degree of body adiposity. Regardless of the concentration of 25(OH)D in blood used to define vitamin D deficiency, hypovitaminosis D was common in these subjects. Conclusion  It is recommended that policies be developed to prevent vitamin D deficiency in adolescent girls. Further studies are needed to identify the mechanisms whereby vitamin D status is related to exercise and to body composition during growth.     

Laparoscopic pyeloplasty in children: Long‐term outcome

Objectives: To asses the safety and efficacy of laparoscopic pyeloplasty in pediatric patients. Methods: Data of pediatric patients under the age of 14 years, who had undergone laparoscopic pyeloplasty from January 2000 to December 2005, were prospectively analyzed. The various parameters recorded were: operative time, blood loss, need for analgesics, intra/postoperative complications, hospital stay and postoperative outcome. Success was defined as either symptomatic improvement and/or better drainage on postoperative isotope renography Results: There were 53 patients with a mean age of 9.12 years (1–14 years) and a male to female ratio of 4.3:1. Dismembered pyeloplasty was done in 41 patients and Foley Y‐V plasty in 12 patients via a transperitoneal approach using 3 ports in 50 children or 4 ports in 3 children. Mean operative time was 181 min (78–369); mean blood loss was 118.01 mL (50–250) with a mean hospital stay of 5.05 days (2–11). Conversion to open surgery was required in 4 (7.54%) patients. Follow‐up renograms were available in 49 patients, which showed improvement in drainage in 44 patients and an obstructed pattern in five; of these, two patients had significant deterioration in split function. Two patients among the obstructed group underwent redo pyeloplasty by open technique while the other three elected for a conservative approach. Thus at a mean follow up of 24.58 months (4–45) the overall success rate was 89.75%. Conclusions: Laparoscopic pyeloplasty is a safe and effective, minimally invasive procedure in pediatric patients with a good intermediate term success rate and minimal morbidity.     

The effect of calcium intake and physical activity on bone quantitative ultrasound measurements in children: a pilot study

Environmental factors, such as nutritional status, physical activity, and drug therapy, can affect bone mineralization. Our objective was to evaluate the relationship between nutritional status, physical activity, and bone mineralization as assessed by multisite quantitative ultrasound technology in children. The study group comprised 67 children, aged 6–17 years (mean, 9.4), attending a primary care clinic. Data on calcium intake and physical activity were collected using a detailed questionnaire. Speed of sound measurements were performed at the distal 1/3 radius and the midshaft tibia using Sunlight Omnisense apparatus. The reported mean calcium intake was 1105 mg/day. There was a significant difference in Z-scores at the radius and tibia between the low-and high-calcium-intake groups (P = 0.004, P = 0.035, respectively). A similar difference was found between the low-and normal-physical-activity groups (P = 0.015, P = 0.036, respectively). In this pilot study, a positive association was found between calcium intake, physical activity, and bone status, as assessed by the quantitative ultrasound technique.     

Long‐term outcome of giant cell tumors of bone around the knee treated by en bloc resection of tumor and reconstruction with prosthesis

Objective: To study the long‐term outcomes and complications of giant cell tumors around the knee treated with en bloc resection and reconstruction with prosthesis. Methods: From January 1991 to March 2005, 19 patients (11 men, 8 women, average age 35.4 years) were treated in our hospital with en bloc resection and reconstruction with domestic prosthesis (15 hinge knee and 4 rotating‐hinge knee). The distal femur was involved in 12 and the proximal tibia in 7 cases. Nine tumors were primary and 10 recurrent. All cases were Campanacci grade III. The affected limb functions were evaluated by the Musculoskeletal Tumor Society scoring system. Results: All patients underwent operation successfully with no complications. The mean follow‐up time was 128.9 months (60 to 216 months). Apart from one patient who underwent amputation because of wound infection two years after reoperation, the range of knee motion of 18 patients was 30°–110°. The mean functional score of the affected limb was 22.7 (15 to 27 points). The length of the lower extremities was equal in nine cases; the affected limb was 2–9 cm shorter in the other ten cases. Prosthesis fracture and loosening developed in one, prosthesis aseptic loosening in three, and delayed deep infection and prosthesis loosening in two cases. The prosthesis loosening rate was 31.6%. One patient developed a proximal femur fracture. Conclusion: En bloc resection and reconstruction with prosthesis is a feasible method for treating giant cell tumor of bone around the knee. Complications related to the prosthesis, mainly prosthesis loosening and limb shortening, increase gradually with longer survival time.     

Long‐term cadmium exposure and the association with bone mineral density and fractures in a population‐based study among women

All people are exposed to cadmium (Cd) via food; smokers are additionally exposed. High Cd exposure is associated with severe bone damage, but the public health impact in relation to osteoporosis and fractures at low environmental exposure remains to be clarified. Within the population‐based Swedish Mammography Cohort, we assessed urinary Cd [U‐Cd, µg/g of creatinine (cr)] as a marker of lifetime exposure and bone mineral density (BMD) by dual‐energy X‐ray absorptiometry (DXA) among 2688 women. Register‐based information on fractures was retrieved from 1997 to 2009. Associations were evaluated by multivariable regression analyses. In linear regression, U‐Cd was inversely associated with BMD at the total body (p < .001), femoral neck (p = .025), total hip (p = .004), lumbar spine (p = .088), and volumetric femoral neck (p = .013). In comparison with women with U‐Cd < 0.50 µg/g of cr, those with U‐Cd ≥ 0.75 µg/g of cr had odds ratios (ORs) of 2.45 [95% confidence interval (CI) 1.51–3.97] and 1.97 (95% CI 1.24–3.14) for osteoporosis at the femoral neck and lumbar spine, respectively. Among never‐smokers, the corresponding ORs were 3.47 (95% CI 1.46–8.23) and 3.26 (95% CI 1.44–7.38). For any first fracture (n = 395), the OR was 1.16 (95% CI 0.89–1.50) comparing U‐Cd ≥ 0.50 µg/g of cr with lower levels. Among never‐smokers, the ORs (95% CIs) were 2.03 (1.33–3.09) for any first fracture, 2.06 (1.28–3.32) for first osteoporotic fracture, 2.18 (1.20–3.94) for first distal forearm fracture, and 1.89 (1.25–2.85) for multiple incident fractures. U‐Cd at low environmental exposure from food in a general population of women showed modest but significant association with both BMD and fractures, especially in never‐smokers, indicating a larger concern than previously known. © 2011 American Society for Bone and Mineral Research.     

Bone and Muscle Development During Puberty in Girls: A Seven‐Year Longitudinal Study

The growth of lean mass precedes that of bone mass, suggesting that muscle plays an important role in the growth of bone. However, to date, no study has directly followed the growth of bone and muscle size through puberty and into adulthood. This study aimed to test the hypothesis that the growth of muscle size precedes that of bone size (width and length) and mass during puberty. Bone and muscle properties were measured using pQCT and DXA in 258 healthy girls at baseline (mean age, 11.2 yr) and 1‐, 2‐, 3–4‐ and 7‐yr follow‐up. Growth trends as a function of time relative to menarche were determined from prepuberty to early adulthood for tibial length (TL), total cross‐sectional area (tCSA), cortical CSA (cCSA), total BMC (tBMC), cortical volumetric BMD (cBMD), and muscle CSA (mCSA) in hierarchical models. The timings of the peak growth velocities for these variables were calculated. Seventy premenopausal adults, comprising a subset of the girl's mothers (mean age, 41.5 yr), were included for comparative purposes. In contrast to our hypothesis, the growth velocity of mCSA peaked 1 yr later than that of tibial outer dimensions (TL and tCSA) and slightly earlier than tBMC. Whereas TL ceased to increase 2 yr after menarche, tCSA, cCSA, tBMC, and mCSA continued to increase and were still significantly lower than adult values at the age of 18 yr (all p < 0.01). The results do not support the view that muscle force drives the growth of bone size during puberty.     

Effects of sodium bicarbonate supplementation on axial and peripheral bone mass in rats on strenuous treadmill training exercise

We observed the effects of sodium bicarbonate supplement on bone mass in rats on strenuous treadmill training. Sixty female Wistar rats (93-days-old; mean initial weight 261 ± 16 g) were studied. One group of 15 rats was killed at the beginning of the experiments (basal control group), while another group of 15 rats was not manipulated (Exer−NaB−). Another group of 15 rats was exercised but did not receive sodium bicarbonate (Exer+NaB−), while the final group of 15 rats exercised and received sodium bicarbonate (Exer+NaB+) at a dose of 0.05 mg/kg/day, administered by esophageal catheter on exercise days. These rats were killed at the end of 11 weeks. Femoral and vertebral length, weight, and bone mineral content (BMC) and density (BMD) were measured. According to anova with the Tukey–Kramer test, femur length and weight, vertebral weight, femur BMC and BMD, vertebral BMC and BMD and the ratio between femur and vertebral BMC and final body weight, and plasma bicarbonate were lower in the basal control and Exer+NaB− groups than in the two other groups (P < 0.005–0.0001). Overall, there was a positive correlation between femur and vertebral BMC and femur BMC and length (P < 0.0001 for all). Only in the Exer+NaB− group was there a positive association between plasma bicarbonate levels and femur length (r = 0.78; P < 0.0005). Our study demonstrates the adverse effects of strenuous exercise on bone, and the usefulness of sodium bicarbonate supplements in preventing and minimized these effects. Received: May 1, 2000 / Accepted: August 11, 2000     

Interactions of interleukin-6 gene polymorphisms with calcium intake and physical activity on bone mass in pre-menarche Chinese girls

Summary  This study assessed independent associations and interactions of IL-6 promoter alleles (−174G/C and −634C/G), calcium intake and physical activity with bone mass among pre-menarche Chinese girls. The −634 CC carriers, greater calcium intake and physical activity were associated with better bone mass. The gene-bone association was more pronounced among girls with high physical activity or with low calcium intake. Introduction  The association between interleukin (IL)-6 promoter polymorphisms and bone mass remains in debate. This cross-sectional study examined the association between the IL-6 promoter alleles (−174G/C and −634C/G) and bone mass, and assessed if the association could be modified by calcium intake or physical activity in pre-menarche Chinese girls. Methods  Two-hundred and twenty-eight healthy pre-menarche girls aged 9–11 years were recruited from primary schools in Guangzhou, China by sending letters to parents. None of them had diseases or medications known to affect bone metabolism. The IL-6 promoter genotypes were determined by PCR-RFLP, and BMD and BMC at the total body, lumbar spine, total hip and femoral neck were measured by DXA. Calcium intake and physical activity were assessed by face-to-face questionnaire interview. Results  One hundred and seventy-six subjects completed the entire study. We did not detect gene polymorphism at the IL-6 −174G/C locus, all were GG homozygotes. The IL-6 −634C/G polymorphism was significantly associated with both BMD and BMC even after adjusting for age and weight. Girls with CC genotype had higher levels of BMC and BMD than G allele carriers (+8.3% for the total body BMC, and +2.9%, +5.8%, and +5.7% for BMDs at the total body, total hip, and femoral neck, respectively; P < 0.05). The favorable effect of physical activity on BMDs at the total hip and femoral neck was much more pronounced in CC carriers than in G allele carriers, and the CC genotype associated higher BMDs at the total hip and femoral neck were observed only in girls with high level physical activity (P for interactions = 0.036 and 0.021, adjusted for age and weight). Calcium had a more benefit to the total body BMC in G allele carriers than in CC carriers, and the G allele-associated lower total body BMC was found only in subjects with low calcium intake. Conclusion  The IL-6 −634C/G polymorphism was significantly associated with BMD and the association might be modified by calcium intake or physical activity in pre-menarche Chinese girls.     

Validation of a physical activity questionnaire to measure the effect of mechanical strain on bone mass

Most of the questionnaires available to estimate the daily physical activity levels of humans are based on measuring the intensity of these activities as multiples of resting metabolic rate (METs). Metabolic intensity of physical activities is the most important component for evaluating effects on cardiopulmonary fitness. However, animal studies have indicated that for effects on bone mass the intensity in terms of energy expenditure (metabolic component) of physical activities is less important than the intensity of mechanical strain in terms of the forces by the skeletal muscles and/or the ground reaction forces. The physical activity questionnaire (PAQ) used in the Amsterdam Growth and Health Longitudinal Study (AGAHLS) was applied to investigate the long-term effects of habitual physical activity patterns during youth on health and fitness in later adulthood. The PAQ estimates both the metabolic components of physical activities (METPA) and the mechanical components of physical activities (MECHPA). Longitudinal measurements of METPA and MECHPA were made in a young population of males and females ranging in age from 13 to 32 years. This enabled evaluation of the differential effects of physical activities during adolescence (13-16 years), young adulthood (21-28 years), and the total period of 15 years (age 13-28 years) on bone mineral density (BMD) of the lumbar spine, as measured by dual-energy X-ray absorptiometry (DXA) in males (n = 139) and females (n = 163) at a mean age of 32 years. The PAQ used in the AGAHLS during adolescence (13-16 years) and young adulthood (21-28 years) has the ability to measure the physical activity patterns of both genders, which are important for the development of bone mass at the adult age. MECHPA is more important than METPA. The highest coefficient of 0.33 (p < 0.01) was between MECHPA measured over the total period of 15 years (13-28 years) and lumbar BMD at age 32 years. Only during adolescence (12-16 years) was METPA more important with regard to lumbar BMD at age 32 years, with a beta of 0.21 (p < 0.01). The relative validity of the PAQ was established by comparing PAQ scores during four annual measurements in 200 boys and girls with two other objective measures of physical activity: movement counters (pedometers) and heart rate monitoring. These showed significant (p < 0.01) correlations in both genders, varying between 0.16 and 0.20. The small variation indicates, however, that all three instruments measure different aspects of physical activity. The results from the PAQ, with respect to MECHPA, validated in humans the results from animal studies in which bone adaptation during skeletal growth and development continuously adjust skeletal mass and architecture to changing mechanical stimuli caused by physical activity.     

Cortical versus trabecular bone mass: Influence of activity on both bone components

Motivated by the controversy in the literature concerning the influence of activity on bone mass and on its cortical and trabecular components, a study was made using computed peripheral tomography (Stratec XCT 900) of the total, cortical, and trabecular bone mass of the dominant and nondominant upper extremities of 50 apparently normal subjects (average age 26±6 years). No differences were observed in the trabecular bone compartment, but the cortical compartment was greater (P<0.001) in the dominant extremity. There was also a significantly greater total bone mass in the dominant extremity which we attributed to greater cortical mass (P<0.025) given the highly significant correlation (r²=0.904, P=0.0001) between total and cortical bone mass and the less significant correlation between total and trabecular bone mass (r²=0.479, P=0.0001).