Exercise, bone mass and bone size in prepubertal boys: one-year data from the pediatric osteoporosis prevention study.

This non-randomized prospective controlled study evaluates a daily school-based exercise intervention program of 40 min/school day for 1 year in a population-based cohort of 81 boys aged 7-9 years. Controls were 57 age-matched boys assigned to the general school curriculum of 60 min/week. Bone mineral content (BMC; g) and areal bone mineral density (aBMD; g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body, the third lumbar vertebra (L3) and the femoral neck (FN). Bone width for L3 and FN was calculated from the lumbar spine and hip scan. No differences between the groups were found at baseline in age, anthropometrics or bone parameters. The mean annual gain in L3 BMC was 5.9 percentage points higher (P<0.001), L3 aBMD a mean 2.1 percentage points higher (P=0.01) and L3 width a mean 2.3 percentage points higher (P=0.001) in the cases than in the controls. When all individuals were included in one cohort, the total duration of exercise including both school-based and spare-time training correlated with L3 BMC (r=0.26, P=0.003), L3 aBMD (r=0.18, P=0.04) and L3 width (r=0.24, P=0.006). The study suggests that exercise in pre-pubertal boys influences the accrual of bone mineral and bone width and that a 1-year school-based exercise program confers skeletal benefits, at least in the lumbar spine.

Daily physical education in the school curriculum in prepubertal girls during 1 year is followed by an increase in bone mineral accrual and bone width--data from the prospective controlled Malmö pediatric osteoporosis prevention study.

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7-9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2-L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm(3)) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7-9 years enhances the accrual of BMC and aBMD and increases bone width.

Pubertal bone growth in the femoral neck is predominantly characterized by increased bone size and not by increased bone density--a 4-year longitudinal study.

Fragility fractures are correlated to reduced bone size and/or reduced volumetric bone density (vBMD). These region-specific deficits may originate from reduced mineral accrual and/or reduced skeletal growth during the first 2 decades of life. Before pathological development can be defined, normal skeletal growth must be described. To evaluate growth of bone size, accrual of bone mineral content (BMC), areal bone mineral density (aBMD) and vBMD in a population-based cohort, 44 boys and 42 girls were followed by annual measurements from the age of 12 to 16 (attendance rates 90-100%). Segmental bone length, bone width, BMC, aBMD and vBMD were measured by dual-energy X-ray absorptiometry (DXA). Data were compared with predicted adult peak, as determined in 36 men aged 27.7+/-4.6 years and 44 women aged 26.8+/-4.9 years. Growth in width of the femoral neck precedes accrual of BMC in the femoral neck in both genders up to age 15. The girls were at all ages closer to their predicted adult peak in both bone width and BMC compared with the boys except in the femoral neck. As femoral neck vBMD had reached its predicted adult peak already at 12 years in both genders, the increase in femoral neck BMC and femoral neck aBMD from age 12 to 16 was most likely to be explained by the increase in bone size. In boys the peak velocity growth was recorded at ~14 years for BMC, height, width and lean mass. Growth from the age of 12 to 16 seems to build a bigger but not a denser skeleton in the femoral neck.

Physical activity increases bone size in prepubertal boys and bone mass in prepubertal girls: a combined cross-sectional and 3-year longitudinal study.

This study evaluates the effect on the skeleton of physical activity from age 9 to 16. In 42 girls and 44 boys, bone mass and bone size were evaluated longitudinally by dual-energy X-ray absorptiometry (DXA) from ages 13 to 16. Physical activity from ages 9 to 13 was cross-sectionally evaluated at baseline (age 13). Girls with high physical activity from ages 9 to 13 at baseline had higher femoral neck bone mineral content (FN BMC; g) (P = 0.07), higher FN areal bone mineral density (FN aBMD; g/cm2), and higher FN volumetric BMD (FN vBMD; g/cm3) (both P < 0.05) compared with girls of low activity. FN width (cm) and head aBMD (an unloaded region) showed no differences when comparing the two groups. Three years of further high and low activity (from ages 13 to 16) did not yield any increased differences between the two groups. Boys with high physical activity from ages 9 to 13, had at baseline higher FN BMC, FN aBMD, and FN width (all P < 0.05) compared with boys with low activity. FN vBMD and head aBMD showed no differences when comparing the two groups. Three years of further high and low activity did not yield any increased differences between the two groups. We conclude that exercise may yield skeletal benefits before age 13, and that 3 years of continued high or low level activity up to age 16 did not yield any increased differences in bone size or bone mass in either girls or boys.

Abnormally decreased regional bone density in athletes with medial tibial stress syndrome.

Medial tibial stress syndrome, a common condition of uncertain origin found in athletes, is characterized by pain in the distal posteromedial aspect of the tibia during exercise, with or without increased scintigraphic uptake in the affected region. To determine whether medial tibial stress syndrome with increased scintigraphic uptake is associated with a change in tibial bone mineral density confined to the site of the increased uptake, we measured bone mineral density (in grams per square centimeter) in 18 adult male athletes with long-standing medial tibial stress syndrome and compared the measurements with those of 16 age- and sex-matched control subjects and with those of 18 athletes without medial tibial stress syndrome who had a comparable training regimen. Tibial bone mineral density in the region corresponding to the pain was 15%+/-9% lower in the patients than in control subjects and 23%+/-8% lower than in the athletic control subjects (both significant differences). Bone mineral densities in most other regions of the body were higher than in the control subjects but lower than in the athletic controls at the corresponding sites. In summary, medial tibial stress syndrome is associated with low regional bone mineral density.

Peripubertal moderate exercise increases bone mass in boys but not in girls: a population-based intervention study.

On the basis of cross-sectional studies in elite athletes and longitudinal studies, physical activity in growing children has been suggested to enhance bone mineral acquisition and prevent osteoporosis later in life. The level of exercise in most of these studies is not applicable in a population on a day-to-day basis. The aim of this study was to determine whether moderate increased exercise within the school curriculum from age 12 to 16 years would have anabolic bone effects. In a population-based setting of 40 boys and 40 girls the school curriculum was enhanced to physical education 4 times per week for 3-4 years. Controls were 82 boys and 66 girls who had had physical education twice a week over a corresponding period. Both cases and controls were measured at age 16 years. Bone mineral content (BMC), areal bone mineral density (aBMD), bone size (femoral neck width) and volumetric BMD (vBMD) were measured in total body, spine and femoral neck (FN) by dual-energy X-ray absorptiometry. Data are presented as mean +/- SD. BMC (8 +/- 15%, p = 0.04), aBMD (9 +/- 13%, p = 0.002) and vBMD (9 +/- 15%, p = 0.001) were all higher in FN in the male intervention group compared with controls. FN bone size was no higher in the intervention group than in the controls. In girls, no differences were found when comparing the intervention group with controls. The results remained after adjusting for confounding factors such as weight, height, milk intake and activity after school. In summary, we report that increased bone mass can be achieved in a population-based cohort of boys (but not in girls) by moderate increased physical activity within the school curriculum from age 12 to 16 years. We speculate that the same results can be seen in girls if intervention starts at an earlier age. We conclude that increasing the physical education content of the Swedish school curriculum may improve bone mass in at least peripubertal boys.

The impact of long-term moderate physical activity on functional performance, bone mineral density and fracture incidence in elderly women.

BACKGROUND: Earlier studies have shown that physical exercise and a higher workload increase muscle strength and improve gait and balance at all ages for both sexes. Published studies have, so far, failed to investigate the functional performance of elderly individuals concerning their long-term physical activity and variables of daily living. OBJECTIVE: To compare elderly women who participate in long-term, moderate exercise programmes with two age-matched groups of women from an urban and a rural community. METHODS: All participants answered a questionnaire about health, social circumstances and fractures. We measured the vibration threshold of the lower extremities, bone mineral density of the distal radius and functional performance such as muscle strength, balance and gait. RESULTS: The elderly, active groups performed significantly better in all functional tests and had sustained fewer fractures than the urban control group. When the comparison was made with the rural control group the differences were less obvious. The active group rated their health as better than both the control groups. CONCLUSION: Elderly women, who continue with moderate exercise programmes over many years, sustain fewer fractures and have better muscle strength, balance, gait and health ratings than women in general. Whether this is the result of the exercise or inherited characters, remains to be proved.

Comparison of quantitative ultrasound measurements in calcaneus with DXA and SXA at other skeletal sites: a population-based study on 280 children aged 11-16 years.

We performed ultrasound measurements (QUS) of the calcaneus in a population-based setting on 280 healthy children, aged 11-16 years, from a small urban area in southern Sweden. The results are compared with dual-energy X-ray absorptiometry (DXA) measurements in the total body, the lumbar spine and the hip, as well as single-energy X-ray absorptiometry (SXA) of the forearm. Normative data and correlations between the three different techniques were determined. We found significant correlations between QUS and age (r = 0.34-0.54), height (r = 0.13-0.56) and weight (r = 0.30-0.60), and between QUS and bone mineral density (BMD) measurements (r = 0.44-0.70). Boys increased all their bone mineral variables with age, whereas girls showed a decreasing trend from age 15 years. QUS had a significantly higher increase in standardized value with age than Ward's triangle BMD, but a significantly lower increase in standardized value with age than distal radius (cortical site) BMD. At other BMD sites we did not find any significant differences compared with QUS regarding changes with age. The measurements obtained by QUS, DXA and SXA, respectively, were divided into, quartiles. Of all subjects in the lowest quartile for QUS measurements, only 34-50% were also in the lowest quartiles for DXA and SXA measurements. In conclusion, QUS measurements of the calcaneus in children show similar results as for adult regarding the correlation with DXA and SXA; they also have a significant correlation with anthropometric data. QUS did not identify the same individuals with low bone mass as the X-ray techniques.

Assessment of sex hormones and bone mineral density in relation to occurrence of fracture in men: a prospective population-based study.

Patients with fragility fractures have low bone mineral density (BMD)--this statement is supported mainly by data on women. In this study, including only men, the objectives were to determine whether a decline in BMD alone or in combination with data on male sex hormones and skinfold thickness could be of value in predicting forthcoming fractures. We also wanted to find out whether high consumers of alcohol can be identified by measuring BMDs and male sex hormones. A prospective, population-based study was performed in the city of Malmö, Sweden. 242 men were randomly selected; all were of Scandinavian ethnic background, and were aged 50, 60, 70, and 80 years. Forearm BMD, testosterone, sex-hormone-binding globulin (SHBG), and skinfold thickness were analyzed. In addition, alcohol consumption and carbohydrate-deficient transferrin (CDT)--a marker of alcohol abuse--were analyzed. The study group was followed prospectively for 7 years and all fractures sustained were recorded. Prospectively, for a 1 SD decrease in forearm BMD, the Cox proportional hazard model gave a relative risk (RR) of 1.75 with a 95% confidence interval of 1.08-2.83 for a forthcoming fracture and 3.88 (1.30-11.57) for a hip fracture. For a 1 SD change in skinfold thickness, measured on the dorsum of the hand, a RR of 1.69 (0.99-2.87) for a forthcoming fracture was found and the corresponding value for hip fracture was 2.34 (1.10-5.00). Testosterone and SHBG did not enhance fracture prediction. Abusers of alcohol had, retrospectively, significantly more fractures. Individuals with alcohol consumption rates in the highest quartile had significantly higher CDT levels, but we were unable to identify high consumers of alcohol by analyzing BMD or sex hormones. In this study we found that forearm BMD and skinfold thickness could be used in predicting forthcoming fractures in men.

Balance and gait performance in an urban and a rural population.

OBJECTIVE: To compare the differences in standing balance and gait performance between two populations, correlated with age and physical activities of daily living. DESIGN: A cross-sectional study. SETTINGS: Malmö, the third largest city in Sweden, and Sjöbo, a typical agricultural community 60 km east of Malmö. PARTICIPANTS: Participants were 570 men and women from the urban community (urban) and 391 from the rural community (rural), born in 1938, 1928, 1918, and 1908, and women born in 1948. The two cohorts were subdivided into true urbans, who had lived only in the city (n = 269), and true rurals, who had never lived in a city (n = 354). MEASUREMENTS: Information about workload, housing, spare time activities, medication, and illness during different decades of life was gathered using two questionnaires. The first questionnaire was sent to the home after agreement to participate, and the second was presented at the test session. The clinical measurements were standing balance, gait speed, and step length. RESULTS: The urban subjects had significantly (P < .001) impaired balance compared with rural subjects. This difference increased with increasing age. The urban subjects walked faster than the rural subjects (P < .001), and the urban subjects used fewer steps than their rural counterparts (P < .001). Spare time activities had a significant influence on the above tests, but, except for gait velocity (P = .011), workload was of minor importance according to analysis of covariance. CONCLUSION: Background factors such as usual daily activities of living and lifestyle seem to be of importance when evaluating and comparing different populations with respect to their balance and gait performance.

Bone mineral density in adolescents. Higher values in a rural area--a population-based study of 246 subjects in southern Sweden.

We performed, in a cross-sectional study, dual energy X-ray absorptiometry (DXA) among 15-16-year-old boys (n 58) and girls (n 44) living in an urban area and among boys (n 82) and girls (n 66) of the same age from a rural area. We measured bone mineral density (BMD) of the total body, the lumbar spine and the hip. In the rural population, we found significantly higher BMD levels in the lumbar spine (14% for the boys and 12% for the girls) and the total body (6.9% for the boys and 3.4% for the girls). We detected no significant differences in the hip BMD. Adolescents in rural areas seem to develop a higher peak bone mass and thereby presumably have a lower risk of developing fragility fractures.

The relationship between childhood growth, bone mass, and muscle strength in male and female adolescents.

In this population-based study, the relationship between childhood weight and height, and adolescent bone mass and muscle strength have been studied in 39 girls and 48 boys. Total body and femoral neck bone mass measurements (bone mineral content, BMC and bone mineral density, BMD) were made by dual X-ray absorptiometry. Quadriceps muscle strength was measured. Mean age at the time of measurement was 15.1 years for girls and boys. Results were individually linked to data on childhood (birth to 6 years of age) weight and height, taken from community health records. Childhood weight was found to be predictive of adolescent total body BMC (TBMC). However, this was not the case when correlating childhood weight and total body BMD (TBMD), suggesting that growth determines the size of the skeleton, whereas the density within that bone envelope is to a greater extent governed by other factors. Further, in a multiple regression model we found that the combined effect of childhood weight and height was significantly correlated with adolescent quadriceps muscle strength.

Bone mineral density, muscle strength and physical activity. A population-based study of 332 subjects aged 15-42 years.

The aim of this population-based study was to find out whether differences in levels of physical activity have an influence on bone mass quantity and whether quadriceps muscle strength is a reliable determinant of bone mass. Included were 175 men and 157 women, aged 15-42 years. Bone mineral density (BMD) was measured at various sites by dual X-ray absorptiometry (DXA) and single photon absorptiometry (SPA). Muscle strength was assessed using an isokinetic muscle force meter. A questionnaire was used to estimate the level of physical activity. We found a positive correlation between physical activity and BMD for boys at the distal forearm and for girls at the trochanter (age group 15-16 years). Active men (age group 21-42 years) had up to 9% higher BMD levels at the hip than those who were less active. Quadriceps muscle torque was not an independent predictor of BMD. Our data suggest that a higher level of physical activity-within the limits of a "normal life style"-may have a positive effect on BMD in the proximal femur of young adults, which in turn may lessen the subsequent risk of fracture.

A single bone density measurement can predict fractures over 25 years.

The purpose of the present study was to determine the predictive ability of a single bone mineral density (BMD) measurement on a 25-year perspective. A group of 1076 women (age 20-78 years) had had their forearm BMD measured from 1970 to 1975. In those women that were still alive at the end of 1994 (n = 410), all fragility fractures (distal end of the radius, proximal end of the humerus, hip, and vertebra) that had occurred after the BMD measurement and that were roentgen verified were recorded, after a follow-up time of 20-25 years. Altogether, 213 fractures occurred in the cohort. In the age group > or = 40-70 (at time of BMD measurement) the relative risk (RR) associated with a 1 SD decrease of forearm BMD was 1.66 (CI 1.13-2.46) for a hip fracture (n = 43), 1.79 (CI 1.22-2.62) for a vertebral fracture (n = 63), and 1.33 (CI 1.20-1.73) for all fractures. In the age group 30-50, a fracture of the distal end of the radius after 20 years could be predicted; RR 1.90 (CI 1.02-3.55). These are slightly lower predictive values compared with previous studies of the same population with follow-up times of 11 and 13 years, especially with regard to hip fractures. However, the present study demonstrates that a single BMD measurement at the forearm has a predictive ability for fragility fractures--including hip fractures--on a 25-year perspective.

Importance of participation rate in sampling of data in population based studies, with special reference to bone mass in Sweden.

OBJECTIVE: To study the effects of participation rate in sampling on "normative" bone mass data. DESIGN: This was a comparison between two randomly selected samples from the same population. The participation rates in the two samples were 61.9% and 83.6%. Measurements were made of bone mass at different skeletal sites and of muscle strength, as well as an assessment of physical activity. SETTING: Malmö, Sweden. SUBJECTS: There were 230 subjects (117 men, 113 women), aged 21 to 42 years. RESULTS: Many subjects participated in both studies (163). Those who took part only in the study with the higher participation rate (67) almost invariably had higher values for bone mass density at the sites measured (up to 7.6% for men) than participants in the study with the lower participation rate. No differences in muscle strength were recorded. CONCLUSION: A high degree of compliance is important to achieve a reliable result in determining normal values in population based studies.

Bone mineral density in female junior, senior and former football players.

The purpose of this study was to examine the bone mineral densities (BMD) of female junior and senior football (soccer) players with different training regimens and histories, female former football players, and their respective controls. Active junior (age 13-17 years, n = 62) and senior (age 18-28 years, n = 34) players, representing three teams with different levels of performance and training, were compared reciprocally and with matched controls (n = 90). Former players (age 34-84 years, n = 25) who had ended their careers on average 9.7 years previously and their matched controls (n = 57) were also studied. Body composition and total body, lumbar spine and proximal femur BMD were measured with dual-energy X-ray absorptiometry. Former players and their controls were asked in a questionnaire to specify their current level of physical activity. In a control for differences in age, weight and body mass index, football players had significantly greater BMD than controls at all sites measured. This difference appeared to be site-specific, with greater differences in BMD at the proximal femur sites (10.5-11.1%) than at the lumbar spine (4.8%) or for the total body (3.5%). Further, differences were greater for senior than for junior players. However, no BMD differences were found between teams representing different levels of performance and training. Female former football players had retained their proximal femur and total-body BMD advantage over controls. In conclusion, training in female football, which is an impact-loading activity, has a site-specific, positive effect on bone formation that is not increased over a certain level of physical activity. The BMD advantage attained appears to be preserved to some extent after the termination of the athlete's active career, which may have a positive effect on future fracture risk.

Assessment of biochemical markers of bone metabolism in relation to the occurrence of fracture: a retrospective and prospective population-based study of women.

We have in a population-based setting evaluated biochemical markers of bone metabolism in 328 women, aged 40-80 years, and related it to contents of bone mineral measurements and the retrospective and prospective presence of fracture. The participants were recruited from the city population files. Serum samples for analysis of osteocalcin (Oc), procollagen I carboxy-terminal extension peptide (PICP), and carboxy-terminal telopeptide of type I collagen (ICTP) were taken, and forearm bone mineral content (BMC) was measured by single photon absorptiometry (SPA). Fracture history was recorded, and the information was verified and supplemented from both radiologic and orthopedic files. Five years later the registration of fractures was repeated. At the initial investigation, Oc was 23% lower in women who had sustained a fracture (n = 37) within 6 years before measurement (6.3 +/- 3.6 microgram/l vs 8.2 +/- 4.2 microgram/l (p = 0.006)), after adjusting for age and BMC difference. PICP and ICTP were not different from values in the women without fracture. However, in women aged 70-80 years with a fracture sustained during the previous 6 years, PICP was lower (128 +/- 32 microgram/l vs 144 +/- 34 microgram/l, p = 0.046). Oc and ICTP were significantly correlated to age and BMC (Oc-age r = 0.36, Oc-BMC r = -0.31, ICTP-age r = 0.44, ICTP-BMC r = -0.24). The correlations of PICP were weaker. Prospectively, logistic regression gave an odds ratio (OR) of 1.8 (p = 0.015) for a low PICP and fracture susceptibility, at a change of 1 SD, independent of age and BMC. In the age bracket 70-80, the odds ratio was 2.4 (p = 0.036). The odds ratio for ICTP, independent of age and BMC, was 1.9 (P = 0.043) for 1 SD decrease and subsequent fracture risk. We concluded that women who had sustained at least one recent fracture had an altered bone turnover with decreased bone formation but an unaltered resorption. Women with retrospectively registered fractures also sustained subsequent fractures. A decrease from the mean of the collagen markers PICP and ICTP was associated with an increased risk for future fracture. Utilizing these biochemical markers of bone metabolism in a female population, PICP and ICTP had a similar influence on the risk of future fracture as forearm BMC (OR = 1.6, p = 0.03).

Soccer after anterior cruciate ligament injury--an incompatible combination? A national survey of incidence and risk factors and a 7-year follow-up of 310 players.

All players in Swedish soccer teams are required to have insurance in the same company. From the archives of the insurance company, all 3,735 injuries reported in 1986 in 188,152 Swedish soccer players were reviewed. Of these, 937 were knee injuries. All players were asked by mail to fill in a questionnaire and 83 percent replied. The patient records from the different hospitals were requested. The anterior cruciate injuries represented one third of the reported knee injuries. The relative risk of sustaining an anterior cruciate ligament injury was increased in female players, in elite players, and in players in the forward position. The odds ratios were 1.6 (1.3-2.1), 3.3 (1.7-6.1) and 1.8 (1.4-2.5), respectively. The injuries occurred at a younger age in females than in males. 50 percent of the injured players were treated with anterior cruciate ligament surgery, predominantly as a reconstructive procedure, with use of a patellar tendon transplant. 30 (20) percent of the players with anterior cruciate ligament injury were active in soccer after 3 (7) years, compared to 80 (50) percent of an injured control population of soccer players. None of the elite players was active at the same level after 7 years. A comparison of anterior cruciate ligament-injured players, whether treated by surgical reconstruction or not, revealed no difference with regard to the proportion of players still playing soccer after 7 years.

The prevalence of gonarthrosis and its relation to meniscectomy in former soccer players.

The prevalence of radiographic signs of gonarthrosis and its relation to knee injuries were studied in 286 former soccer players--215 nonelite and 71 elite players--and were compared with 572 age-matched controls with a mean age of 55 years. The prevalence of gonarthrosis among the nonelite players was 4.2%, among the elite players 15.5%, and among the controls 1.6%. Seven of the soccer players had known anterior cruciate ligament injuries, and 40 had had meniscectomies. Of the 32 nonelite players with knee injuries, 4 (13%) had gonarthrosis, and of the 183 without known knee injuries 5 (3%) had gonarthrosis. Among the elite players, the prevalence of gonarthrosis in knees without diagnosed injuries was 11%. We conclude that soccer, especially at an advanced level, is associated with an increased risk for gonarthrosis. After excluding subjects with known knee injuries, there was no difference between nonelite players and controls, but we found a higher rate of gonarthrosis among the elite players.