Precision of dual-energy x-ray absorptiometry in determining bone mineral density and content of various skeletal sites.

Repeated measurements of bone mineral density (BMD) by dual-energy x-ray absorptiometry (DEXA) reliably indicate changes in the bone mineral content (BMC) of the lumbar spine and proximal femur, but its applicability to other sites has not been properly determined. The in-vivo day-to-day precision of DEXA (Norland XR-26) for lumbar spine, femoral neck, distal femur, patella, proximal tibia, calcaneus and distal radius was evaluated for 15 subjects who were scanned three times for 2 wk. Intra- and interobserver errors were also determined for image analysis. For clearly defined regions of interest, the following precision values were obtained for BMD with low intra- and interobserver error: 1.7% (lumbar spine), 1.3% (femoral neck), 1.2% (distal femur), 1.0% (patella), 0.7% (proximal tibia), 1.3% (calcaneus) and 1.9% (distal radius). The precision for BMC was lower. The results indicate that DEXA can successfully and precisely measure BMD of sites not commonly assessed by this technique.     

Dual-photon bone mineral density in the proximal femur: correlation by site

Using 153Gd dualphoton absorptiometry, bone mineral density (BMD) was measured in three areas of the proximal femur-the femoral neck, Ward's triangle and the greater trochanter-in 129 females referred for possible osteoporosis. In addition, lumbar spine bone density was determined. Lumbar spine BMD was significantly greater than any regional proximal femoral BMD (p less than 0.0001). Ward's triangle was significantly less than the trochanteric region (p less than 0.01) and both Ward's triangle and the greater trochanter were significantly less than the femoral neck (p less than 0.0005). Correlations within the three regions of the proximal femur are considerably higher than those between the spine and the proximal femur regions. This suggests that measurement of all three areas of the proximal femur is not essential for a satisfactory assessment of proximal femoral mineral content. In particular, since Ward's triangle is strongly correlated with the greater trochanter and the femoral neck, it may rationally be excluded from analysis of proximal femoral bone density.     

The effects of swimming training on bone tissue in adolescence

The aim was to analyze bone mineral content (BMC) and density (BMD) in regular swimming trained adolescents and the interaction that weigh‐bearing sports may have on these values. Bone mass was evaluated by dual energy x‐ray absorptiometry (DXA) and quantitative ultrasound (QUS) in 77 swimmers (34 females/43 males) and 52 normoactive controls (CG; 23 females/29 males) from 11 to 18 years. Swimmers who had performed or were performing other sports (OSP; 11 females/20 males) were compared with pure swimmers (PSW; 23 females/23 males). Both groups were compared with CG. Bone values were compared using analyses of covariance adjusting for height, calcium intake, subtotal lean (whole body lean minus head), and pubertal status. Male PSW showed lower BMD and BMC at several sites than male CG. However, for male OSP, only lumbar spine BMC was lower in OSP than male CG. Male PSW showed lower BMD and BMC when compared with male OSP. Female PSW showed higher arm BMD and lower leg BMC than female CG, while female OSP only presented lower leg BMC than female CG. Contrary to males, female‐PSW presented higher BMD and BMC than female OSP. No differences in QUS values were found between swimmers and CG. To summarize, although more information is needed for females, it seems that for males, swimming is associated with lower BMC and BMD.     

Lean body mass and leg power best predict bone mineral density in adolescent girls

PURPOSE: We evaluated anthropometric and performance measures that best predict bone mineral density (BMD) and bone mineral content (BMC) in 54 adolescent girls (14.6 +/- 0.5 yr; 22.7 +/- 14.0 months past menarche). METHODS: Whole body, femoral neck, greater trochanter, lumbar spine (L2-L4), and mid-femoral shaft BMD and BMC, and whole body bone-free lean mass and fat mass were assessed using DXA (Hologic QDR 1000/W). Knee extensor strength and leg power were assessed by isokinetic dynamometry and the Wingate Anaerobic Power Test, respectively. RESULTS: Whole body lean mass was correlated with BMD at all bone sites (r = 0.45-0.77; P < 0.001) and was more highly correlated with bone at all sites than was body weight. Leg power was also associated with BMD at all sites (r = 0.41-0.67; P < 0.001), whereas leg strength correlated significantly with all sites (r = 0.41-0.53; P < 0.001) except the lumbar spine. Stepwise regression analyses revealed that 59% of the variance in whole body BMD was predicted by lean mass alone. No other variables, including fat mass, height, months past menarche, leg power, or leg strength, contributed additionally to the regression model. Similarly, lean mass was the only predictor of lumbar spine and femoral shaft BMD (R2 = 0.25, R2 = 0.37, respectively), while femoral neck and trochanteric BMD were best predicted by leg power (R2 = 0.38, R2 = 0.36, respectively). Similar but stronger models emerged using BMC as the outcome, with lean mass and leg power explaining the most variance in BMC values. CONCLUSION: In this group of adolescent girls, lean body mass and leg power best predicted BMC and BMD of the whole body, lumbar spine, femoral shaft, and hip, which may suggest an important role for muscle mass development during growth to maximize peak bone density.     

High bone mineral density in loaded skeletal regions of former professional football (soccer) players: what is the effect of time after active career?

Objectives: Physical exercise is an important factor in the acceleration and maintenance of bone mineral density (BMD). Football is an impact loading sport and some studies demonstrate its site specific, bone mass increasing effect. We compared BMD at different skeletal regions in a group of former professional football players and in normal control subjects and evaluated the effect of demographic factors and time after active career on BMD.

Methods: Twenty four former football players <70 years old who had retired from professional football at least 10 years previously and 25 non-athletic controls were recruited. The demographic characteristics, activity levels, and dietary habits of all subjects and the chronological history of the footballers' professional careers were noted. BMD was measured by DEXA at the calcaneus and distal tibia and at the lumbar spine, proximal femur, and distal and proximal radius, and compared between groups. Stepwise multiple linear regression analysis was used to determine the probable predictors of BMD in former football players.

Results: In former players BMD values were found to be significantly higher at the lumbar spine, femur neck, femur trochanter, distal tibia, and calcaneus, but not at Ward's triangle (femur) or the distal and proximal radius regions compared with controls. Time after active career was the only independent predictor of BMD at the lumbar spine, proximal femur (neck, trochanter, and Ward's triangle), and distal tibia.

Conclusions: Former footballers had higher BMD at weight loaded sites and time after active career seemed to be an important factor in determining BMD.

     

不同年限及方式踢毽锻炼中老年男性BMC和BMD的比较

目的:分析比较不同年限及方式踢毽锻炼中老年男性骨矿含量(BMC)和骨密度(BMD)的不同。方法:选取每周踢毽5～7次、每次2～4小时的40～60岁男性27例,按踢毽年限和目前踢毽方式分为踢毽I组(3～12年,双腿踢毽,13例)和踢毽II组(1～3年,单腿踢毽,14例),另选不常运动的16例同龄男性为对照组。采用双能X线骨密度扫描仪测试BMC和BMD,比较分析三组全身和10个部位(头部、胸椎、腰椎、骨盆、非优势臂、优势臂、左肋、右肋、非优势腿、优势腿),以及组内两臂、两肋、两腿的BMC和BMD差异。结果:两踢毽组受试者全身BMC、全身BMD均显著高于对照组(P<0.05,P<0.01)。局部比较:踢毽II组优势腿、非优势腿、骨盆3个部位BMD和非优势腿BMC均显著高于对照组(P<0.05,P<0.01);踢毽I组除左肋外的其他9部位BMC和全部10个部位BMD均显著高于对照组(P<0.05,P<0.01)。双侧比较:踢毽II组非优势腿BMD显著高于优势腿(P<0.05,P<0.01)。结论:长期踢毽锻炼中老年男性全身BMC和BMD较无运动男性更高;踢毽年限越长,获得更高BMC和BMD的部位越多,在下肢和骨盆部位更明显;长期单腿踢毽可能造成两腿BMD发展不均衡。     

High femoral bone mineral content and density in male football (soccer) players

PURPOSE: This investigation examined the effect that long-term football (soccer) participation may have on areal bone mineral density (BMD) and bone mineral content (BMC) in male football players. METHODS: Dual energy x-ray absorptiometry (DXA) scans were obtained in 33 recreational male football players active in football for the last 12 yr and 19 nonactive subjects from the same population. Both groups had comparable age (23 +/- 4 yr vs 24 +/- 3 yr), body mass (73 +/- 7 kg vs 72 +/- 11 kg), height (176 +/- 5 cm vs 176 +/- 8 cm), and calcium intake (23 +/- 10 mg.kg(-1).d(-1) vs 20 +/- 11 mg.kg(-1).d(-1) (mean +/- SD). RESULTS: The football players showed 8% greater total lean mass (P < 0.001), 13% greater whole-body BMC (P < 0.001), and 5 units lower percentage body fat (P < 0.001) than control subjects. Lumbar spine (L2-L4) BMC and BMD were 13% and 10% higher, respectively, in the football players than in the control subjects (P < 0.05). Furthermore, football players displayed higher femoral neck BMC (24%, 18%, 23%, and 24% for the femoral neck, intertrochanteric, greater trochanter, and Ward's triangle subregions, respectively, P < 0.05) and BMD (21%, 19%, 21%, and 27%, respectively, P < 0.05) than controls. BMC in the whole leg was 16-17% greater in the football players, mainly because of enhanced BMD (9-10%) but also because of bone hypertrophy, since the area occupied by the osseous pixels was 7% higher (867 +/- 63 cm2 vs 814 +/- 26 cm2, P < 0.05). Leg muscle mass was 11% higher in the football players than in the control subjects (20,635 +/- 2,073 g vs 18,331 +/- 2,301 g, P < 0.001). No differences were found between the legs in either groups for BMC, BMD, and muscle mass. Left leg muscle mass was correlated with femoral neck BMC and BMD (P < 0.001), as well as with lumbar spine (L2-L4) BMC and BMD (P < 0.001). CONCLUSION: Long-term football participation, starting at prepubertal age, is associated with markedly increased BMC and BMD at the femoral neck and lumbar spine regions.     

Upper-limb bone mineral density of female collegiate gymnasts versus controls

PURPOSE: We examined bilateral bone mineral density (BMD) in the arms of female college gymnasts to assess the relative contribution of high-impact loading forces versus daily activities on bone plasticity. METHODS: Twenty-five female collegiate gymnasts and 25 controls were studied. BMD of the lumbar spine, proximal femur, and whole body were assessed via dual energy x-ray absorptiometry. Upper-limb BMD was determined by custom analyses of the whole-body scans to examine arms individually. RESULTS: BMD of gymnasts was significantly (P < 0.0001) greater than controls at all sites. Whole-body BMD was 8% higher in gymnasts (1.270 +/- 0.078 vs 1.175 +/- 0.073 g x cm(-2)), with 18-19% differences in the lumbar spine (1.427 +/- 0.144 vs 1.212 +/- 0.106 g x cm(-2), right proximal femur (1.298 +/- 0.101 vs 1.100 +/- 0.129 g x cm(-2)), and left proximal femur (1.293 +/- 0.111 vs 1.104 +/- 0.133 g x cm(-2)). Arm BMD was 17% greater in gymnasts, with higher values in both dominant (1.013 + 0.067 vs 0.875 + 0.066 g x cm(-2)) and nondominant (1.002 + 0.060 vs 0.849 + 0.062 g x cm(-2)) arms. Intragroup comparisons revealed a significantly (P < 0.0001) greater BMD in the dominant arm of the controls but no side-to-side difference in the arms of the gymnasts. CONCLUSIONS: Upper-limb BMD followed use patterns in both gymnasts and controls, demonstrating that the forces imposed on the arms with gymnastics training enhanced BMD and resulted in no bilateral differences. These findings illustrate the association between gymnastics training and increased BMD throughout the body, suggesting that the high BMD values observed in gymnasts are due primarily to the activity itself rather than selection bias.     

Effect of exercise training programme on bone mineral density in novice college rowers.

Exercise has important effects on skeletal mineralization. Changes in bone mineral density (BMD) and bone mineral content (BMC) as measured by dual energy X-ray absorptiometry were investigated in a group of 17 male novice college oarsmen over a 7-month period and were compared with eight age-matched controls. The rowing training programme consisted of approximately 8 h rowing, 1 h weight training, and 1 h running per week. After 7 months training the mean BMD of the lumbar spine (L1-L4) had increased significantly by 2.9% (P < 0.001) and the mean BMC had increased by 4.2% (P < 0.001). There was no significant change in the control group. Neither group showed a significant change in BMD or BMC in the femoral neck, greater trochanter or Ward's triangle. This study provides further evidence that exercise plays an important role in bone mineral formation.     

双能X线骨密度仪iDXA机型测量的精确性评估

目的 评估双能X线骨密度测量仪(DXA)iDXA机型测量腰椎、股骨骨密度和全身及其各部位骨密度和体成分含量(肌和脂肪)的精确性.方法 选取30名志愿者.每名志愿者均在同一天内完成2次DXA测量.DXA机型为美国Lunar公司生产的iDXA机型;测量部位包括腰椎、股骨近端和全身;用变异系数(CV)平均方根代表精确性.结果 腰椎和股骨近端各部位骨密度的平均精确性值在0.8%～2.0%之间;其中腰椎和全髋骨密度测量的精确性值最好(0.8%),Ward三角区的精确性值最差(2.0%);全身及各部位骨密度的平均精确性值在0.7%～2.0%之间;其中全身骨密度测量的精确性最好(0.7%);全身及各部位肌组织测量的平均精确性值范围在0.6%～2.1%之间,其中全身肌组织测量的精确性为0.6%.全身及各部位脂肪含量测量的平均精确性值范围1.0%～3.2%之间,其中全身脂肪测量的精确性为1.0%.结论 iDXA测量腰椎、股骨骨密度和全身密度的精确性可满足骨质疏松症诊断和随访的需要;全身各部位肌组织和脂肪测量的精确性结果可有助于今后临床测量的参考.     

Association of the presence of bone bars on radiographs and low bone mineral density

Objective  

Bone bars (BB) are struts of normal trabecular bone that cross the medullary portions of the metaphysis and diaphysis at right angles to the long axis of the shaft. The purpose of this investigation was to determine whether the presence of bone bars (BB) identified on radiographs of the proximal femurs and tibia, predict lower bone mineral density (BMD) as evaluated with dual-energy x-ray absorptiometry (DXA) in the lumbar spine, total hip, or femoral neck.     

Skull bone mass deficit in prepubertal highly-trained gymnast girls.

It is known that impact loading sport can increase the bone mineral density in the stressed sites of the skeleton in athletes. However, non weight-bearing sites are seldom studied in healthy young girl athletes. In order to study the effects of a long term intensive training on the non-stressed region of the skeleton (skull), we investigated both highly-trained girl athletes, involved in sports requiring or not significant impact loading on the skeleton and a girl control group. Bone mineral content (BMC) and density (BMD) were measured in the whole body, at lumbar spine, femoral neck, trochanter, Ward's triangle, radius, head and ribs, in 60 prepubertal girls including 12 swimmers, 32 gymnasts and 16 controls. Measurements were made by DXA. There were no statistical differences between the groups as regards age, height, body weight, body mass index, lean tissue mass and dietary calcium intake. Mean BMD in gymnasts was statistically higher than in other groups for radius (p < 0.001), femoral neck (p < 0.05) and Ward's triangle (p < 0.05) while there was no difference between swimmers and controls. Head BMC was significantly lower in gymnasts compared to other groups (241.9+/-41 g vs. 285.8+/-34.7 g and 291.1+/-50.2 g respectively in swimmers and controls, p < 0.001). The same observation was made for head BMD (p < 0.01). When body weight was used as a covariant, the contribution of the head BMC to the whole body was significantly lower (p < 0.001) in gymnasts (24.97%) than in swimmers (27.88%) and controls (27.77%). When compared between groups, the slopes of the regressions for head/whole body BMC or BMD were significantly lower in gymnasts (p < 0.05) than in other groups. These data suggest that in prepubertal children the increased bone density induced by gymnastic training in the stressed sites of the body could be related to a decreased skull bone mass.     

运动锻炼对30d-6°头低位卧床所致承重骨丢失的影响

目的观察下肢肌力锻炼和功率车锻炼对30 d-6°头低位卧床引起骨丢失的防护效果,为筛选航天员暴露于空间微重力环境下运动锻炼方法提供参考。方法15名男性青年受试者分为卧床对照组、下肢肌力锻炼组和功率车锻炼组,每组5人,在30 d-6°头低位卧床期间,两个运动锻炼组共进行了25 d(次)的运动锻炼,下肢肌力组每天锻炼16~18 min,功率车组每天锻炼30 min。分别于卧床前和起床后测量了全身骨密度(BMD QDR-4500/W Hologic)和腰椎骨小梁比值(CTPhilips-Mx-8000)。结果与卧床前相比,对照组卧床以后全身骨矿含量显著下降(P0.05)、左髋总骨密度和右髋大转子骨密度显著下降(P0.01),第2~4腰椎骨小梁比值显著下降(P0.05),功率车锻炼组虽然全身骨密度显著增加,但是第3~4腰椎骨密度却显著下降(P0.05),下肢肌力锻炼组全身和腰椎及髋部等承重部位的骨矿含量和骨密度均无明显下降。结论30 d-6°头低位卧床可引起腰椎和髋骨等承重部位明显的骨丢失,功率车锻炼方法不能改善腰椎部位的骨丢失,下肢肌力锻炼方法对于维持全身和承重部位的骨密度具有明显的防护效果,该结果将对我国载人航天飞行失重对抗措施方案的制定提供重要的参考。     

Age-predicted values for lumbar spine, proximal femur, and whole-body bone mineral density: results from a population of normal children aged 3 to 18 years.

We measured areal bone mineral density (BMD) with dual-energy X-ray absorptiometry (DXA) at the lumbar spine and the proximal femur and for the total body in 179 subjects (91 girls and 88 boys) with no known disorders that might affect calcium metabolism. Results are also reported for lumbar spine bone mineral content (BMC) and for the derived variable, bone mineral apparent density (BMAD). Expected-for-age values for each variable were derived for boys and girls by using an expression that represented the sum of a steady increase due to growth plus a rapid increase associated with puberty. Normal ranges were derived by assuming that at least 95% of children would be included within 1.96 population standard deviations (SD) of the expected-for-age value. The normal range for lumbar spine BMD derived from our population of children was compared with previously published normal ranges based on results obtained from different bone densitometers in diverse geographic locations. The extent of agreement between the various normal ranges indicates that the derived expressions can be used for reporting routine spine, femur, and whole-body BMD measurements in children and adolescents. The greatest difference in expected-for-age values among the various studies was that arising from intermanufacturer variability. The application of published conversion factors derived from DXA measurements in adults did not account fully for these differences, especially in younger children.     

Bone mineral density in healthy normal women and reproducibility of measurements in spine and hip using dual-energy X-ray absorptiometry.

Bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA) has been measured in 394 healthy normal women. BMD is highest at the end of the 3rd decade and declines from 45 to 75 years by 0.0095 g/cm2/year in the lumbar spine and by 0.0052-0.0078 g/cm2/year in the upper femur depending on the site. BMD appears to increase in the 8th decade. Reproducibility (coefficient of variation (CV) of repeated measurements) was lowest in the lumbar spine (1.45%) and highest in Ward's triangle (4.29%). CV was not influenced by age at any site and by osteoporosis only in the femoral neck. BMD increased from L2 to L4 but the increase could not wholly be accounted for by the size of the vertebra, suggesting that the posterior elements were contributing to the observed increase of bone density.     

Does previous participation in high-impact training result in residual bone gain in growing girls? One year follow-up of a 9-month jumping intervention

The skeletal response to exercise and training on bone is exceptionally good during the growing years. However, it is not known whether the benefit of training on bone is maintained after the training. This 20-month follow-up study assessed the effect of a 9-month jumping intervention on bone gain and physical performance in 99 girls (mean age 12.5 +/- 1.5 years at the beginning of the study) one year after the end of the intervention. Both bone mineral content (BMC), by dual energy X-ray absorptiometry (DXA) at the lumbar spine and proximal femur, and physical performance parameters (standing long jump, leg extension strength, and shuttle run tests) were measured at baseline and at 20 months. A multivariate regression analysis was first used to determine the best predictors of the BMC accrual by time. Analysis showed that age at baseline and square of age, changes in height and weight, and pubertal development into Tanner stages 4 and 5 during the follow-up explained the majority of the BMC gain. Then, the effect of participation in the 9-month exercise intervention on BMC accrual and physical performance was analysed adding this variable (participation: yes/no) into the model. The regression analysis showed that the trainees (N = 50) had 4.9 % (95 % CI, 0.9 % to 8.8 %, p = 0.017) greater BMC increase in the lumbar spine than the controls (N = 49). The mean 20-month BMC increase in the lumbar spine was 28 % (SD 19) in the trainees compared to 22 % (12) increase in the controls. In the proximal femur, the trend was similar but the obtained 2 to 3 % higher BMC accrual in the trainees (compared to that in controls) were statistically insignificant. Among the performance variables, using the same model that best predicted the BMC accrual, the only statistically significant between-groups difference, in favour of the trainees, was the improvement in the standing long jump test (6.4 %, 95 % CI, 2.3 % to 10.4 %, p = 0.002). Improvements in the leg extension strength and shuttle run tests showed no between-groups difference. In conclusion, although the greatest proportion of bone mineral accrual in growing girls is attributable to growth, an additional bone gain achieved by jumping training is maintained at the lumbar spine at least a year after the end of the training.     

The muscle strength and bone density relationship in young women: dependence on exercise status

AIM: Numerous studies report an association between muscle strength and bone mineral density (BMD) in young and older women. However, the participants are generally non-athletes, thus it is unclear if the relationship varies by exercise status. Therefore, the purpose was to examine the relationships between BMD and muscle strength in young women with markedly different exercise levels. METHODS: Experimental design: cross-sectional. Setting: a University research laboratory. Participants: 18 collegiate gymnasts and 22 age- and weight-matched recreationally active control women. Measures: lumbar spine, femoral neck, arm, leg and whole body BMD (g/cm(2)) were assessed by dual X-ray absorptiometry. In addition, lumbar spine and femoral neck bone mineral apparent density (BMAD, g/cm(3)) was calculated. Handgrip strength and knee extensor and flexor torque (60 degrees /s) were determined by dynamometry, and bench press and leg press strength (1-RM) using isotonic equipment. RESULTS: BMD at all sites and bench press, leg press and knee flexor strength were greater in gymnasts than controls (p<0.001). In controls, knee extensor torque was significantly correlated to femoral neck, limb and whole body BMD (r=0.47-0.55, p<0.05), leg press strength was associated with limb and whole body BMD (r=0.52-0.74, p<0.05), and bench press strength with arm BMD (r=0.50, p=0.019). In partial correlations controlling for weight, leg press strength was related to leg and whole body BMD (r=0.46-0.63, p<0.05). There was no association between muscle strength and BMD in gymnasts. CONCLUSION: These results suggest that the association between muscle strength and BMD in young women is dependent on exercise status. The osteogenic effect of increased mechanical loading associated with gymnastics training likely contributes to the dissociation of the relationship in gymnasts.     

Accuracy of lumbar spine bone mineral content by dual photon absorptiometry

The accuracy of measurement of the bone mineral content (BMC, g) and bone mineral density (BMD, g/cm2) of the lumbar spine by dual photon absorptiometry (DPA) was estimated by means of two different spine scanners (a Nuclear Data 2100 and a Lunar Radiation DP3). The lumbar spines of 13 cadavers were used. BMC and BMD were measured in situ and on the excised vertebrae in a solution of water/ethanol; and covered with ox muscle/porcine muscle/lard. The actual mineral weight and areal density were determined after chemical maceration, fat extraction, drying to a constant weight, ashing for 24 hr at 600 degrees C, and correction for the transverse processes. The true are was measured by parallax free X rays and planimetry. All measurements of BMC or BMD were highly interrelated (r = 0.94-0.99). The standard error of estimate (s.e.e.) of BMC in situ versus BMC in water/ethanol was 5.2%. The agreement between the BMD values of the two scanners was very good (s.e.e. = 2.9%). BMC in situ predicted the actual vertebral mineral mass with an s.e.e. of 8.1%. BMD in situ and BMD in water/ethanol predicted the actual area density with s.e.e.s of 10.3% and 5.0%, respectively. This study discloses the correlation and accuracy error of spinal DPA measurements in situ in whole cadavers versus the actual BMC and BMD. The error, which is underestimated in in vitro studies, amounts to 10%.     

Normative data for lumbar spine bone mineral content in children: influence of age, height, weight, and pubertal stage

In 136 normal growing children between the ages of 1 and 18 yr, bone mineral content (BMC) at the level of the lumbar spine (L2-L4) was determined with a commercial dual-photon absorptiometer. BMC was calculated as BML (BMC per unit length) and BMD (BMC per unit surface). The mean lumbar spine BML of the studied children (2.53 +/- 0.86 gHA/cm) was significantly lower than the spinal mineral content of adults (4.26 +/- 0.57 gHA/cm). No sex difference existed in lumbar spine BMC. BML as well as BMD were highly dependent on age, body height, and body weight. During the prepubertal years, BML and BMD increased in a fairly rectilinear pattern. During puberty, BMC increased more rapidly: 40% for BMD and 77% for BML. For the entire group, the increase in BMC with age, height, and weight was best predicted by an exponential regression line analysis.     

Bone mineral density and muscle strength in female ice hockey players

The purpose of this study was to investigate bone mineral density (BMD) at different sites in female ice hockey players as well as to study the relationship between BMD, muscle strength, and body composition parameters. The study group consisted of 14 female ice hockey players (age 22.2 +/- 4.3 years) which was compared with 14 inactive females (age 21.5 +/- 3.8 years). The two groups were matched for age and weight. Areal bone mineral density was measured in total body, head, lumbar spine, femoral neck, Ward's triangle and the trochanter, using dual energy X-ray absorptiometry. Body composition parameters were derived from the total body scan. Isokinetic concentric peak torque of the left quadriceps and hamstrings muscles was measured using an isokinetic dynamometer. Compared to the inactive group, the ice hockey players had significantly higher BMD of all of the bone sites measured, except for the head, (total body 6.9%, head -2.6%, lumbar spine 8.9%, femoral neck 17.6%, Ward's triangle 20.4%, and trochanter 21.7%). The hockey players also had significantly higher peak torque in the quadriceps and hamstrings muscles. In the ice hockey group, a significant positive correlation was found between BMD of the femoral neck and hamstrings peak torque at 225 degreesisecond (r = 0.67, P < 0.01). In the inactive group, significant positive correlations were found between BMD and peak torque in the hamstrings muscles (90 degrees/second: r = 0.6-0.8, P<0.05 (total body, trochanter) and P<0.01 (spine, neck), 225 degrees/second: r = 0.5-0.8, P<0.05 (total body, Ward's triangle, trochanter) and P< 0,01 (spine, neck)). In the inactive group significant positive correlations was also found between lean body mass and BMD of the trochanter (r = 0.58, P < 0.05). In young females it appears that training and playing ice hockey might influence BMD and muscle strength in a positive direction. The correlation between BMD and muscle strength seems to weaken with increased exercise level.