OVERVIEW OF EXERCISE AND BONE MASS

Effects of Zumba® and Aquagym on Bone Mass in Inactive Middle-Aged Women

Background and objectives: Regular exercise may stimulate bone formation and reduce the loss of bone mass in premenopausal women. This study aims to evaluate the effect of high-impact physical activity (Zumba^®) and low-impact physical activity (Aquagym) on bone mass in inactive middle-aged women. Materials and methods: Fifty-five healthy inactive women (30⁻50 years old) were recruited in Spain in 2016 and were randomly allocated into one of three groups: High impact group (HIG: n = 15), low impact group (LIG: n = 12) and control group (CG: n = 28). HIG and LIG were recruited from Madrid and the CG from Toledo. HIG and LIG completed a 12-week intervention program with three 40' sessions per week of Zumba^® or Aquagym; respectively. Dual energy X-ray absorptiometry (DXA) measured bone mineral content (BMC) and areal bone mineral density (aBMD) at total body less head (TBLH), lumbar spine and right hip. Results: Post-intervention adjusted data showed no significant differences in BMC between any of the groups nor in aBMD between HIG and LIG. Interestingly; significant differences for the HIG vs. CG were found in the change in total hip aBMD (1.76% vs. -0.44%), femoral neck aBMD (1.80% vs. -2.71%), and intertrochanter aBMD (2.03% vs. -0.50%). Moreover, significant differences for the LIG vs. CG were also found in the change in femoral neck aBMD (-0.54% vs. -2.71%). Conclusions: The regular practice of Zumba^® and Aquagym might reduce the progressive deterioration of bone mass in inactive middle-aged women.

The bone response to non-weight-bearing exercise is sport-, site-, and sex-specific

OBJECTIVE

To examine whether skeletal adaptations to chronic non-weight-bearing exercise depend on the type of aquatic exercise (swimming or water polo) as well as on sex (men or women).

DESIGN, SETTING, AND PARTICIPANTS

This was a cross-sectional study at the Laboratory of Nutrition and Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, Athens, Greece. A total of 43 water polo players, 26 swimmers, and 30 sedentary individuals, aged 17 to 34 years, were recruited (52 men, 47 women).

MAIN OUTCOME MEASURES

Bone mineral content (BMC) and areal bone mineral density (aBMD) of the total body and of various subregions.

RESULTS

: Compared with controls, swimmers had lower leg and total aBMD (P < 0.05), whereas water polo players had lower leg but higher arm and trunk aBMD (all P < 0.05). Swimmers and water polo athletes differed at the arms (men only), trunk, and total body (all higher in water polo players, at P < 0.05). Bone adaptations to water polo playing were unaffected by sex. Female swimmers, but not male swimmers, had 13% higher arm BMC than controls (P < 0.05), whereas male swimmers, but not female swimmers, had 12% lower leg BMC than controls (P < 0.05).

CONCLUSIONS

Athletes participating in long-term water polo playing and swimming have substantially different total and regional aBMD. The effect is not mediated by sex in water polo players; however, sex may mediate the differences between swimmers and controls. Whether the observed differences between athlete groups and sexes arise from different bone adaptations to activity or from other factors cannot be answered by the current data.

CLINICAL RELEVANCE

Water polo playing may be preferable over swimming for maintaining bone health; both types of aquatic exercise at the elite level of participation, however, have unfavorable effects on the lower limb bones.

Side-to-side differences in cortical bone mineral density of tibiae in young male athletes

The importance of physical activity in the development and maintenance of bone mineral density (BMD) is widely accepted. However, the effects on cortical BMD have not been clarified in detail. The present study examined bilateral asymmetries in cortical BMD of the tibia using peripheral quantitative computed tomography. Subjects comprised 37 young male athletes and 57 controls (age range, 18-28 years). BMD and geometrical indices were determined in bilateral tibiae. Cortical and trabecular BMD were calculated at the diaphysis and distal metaphysis, respectively. Cortical width, periosteal cross-sectional area, and cross-sectional moment of inertia were calculated using tomographic data of the tibial diaphysis. In athletes, the non-dominant leg showed greater cortical BMD than the dominant leg (mean difference, 5.42%; P < 0.0001). Cortical width and moment of inertia were also greater in the non-dominant leg. Periosteal area displayed no significant difference between legs. The control group exhibited similar results except for cortical BMD. No differences in trabecular BMD were noted between legs in either athletes or controls. These results implies the existence of mechanisms for the mechanical adaptation of cortical BMD. Dominant leg is used for mobility or manipulation whereas the non-dominant leg contributes to support the actions of the dominant leg. Loading differences in bilateral legs in young athletes might affect the remodeling rate leading to the side-to-side differences in cortical BMD.

Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs

The bone response to exercise is site-specific and load-dependent. Recent evidence suggests that an inverse relationship may exist between loaded and unloaded sites, such that the former may benefit at the expense of the latter. The present study examined this possibility in 48 males (21 water polo players, 12 handball players, and 15 sedentary controls). Water polo and handball are alike with respect to the active loading of the upper limbs during overhead throwing; however, the weight-supporting environment of water polo removes the weight-bearing effect from the lower limbs. Bone mineral content (BMC), bone projected area (Ap), and areal bone mineral density (aBMD) of the total body and of various subregions were determined by dual-energy X-ray absorptiometry. After adjusting for age, height, and weight, water polo players had higher arms BMC, Ap, and aBMD (by 22.2, 11.1, and 10.5%, respectively; P<0.05), but lower legs aBMD (-6.3%; P<0.05) relative to controls. On the contrary, compared to controls, handball players had higher BMC (from 11.8 to 24.3%), Ap (from 5.2 to 11.7%), and aBMD (from 6.4 to 11.9%) for the total body at all sites. Water polo athletes had increased arms and decreased legs aBMD ratios (regional-to-total) than either handball players or sedentary subjects (P<0.001). Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs, with no major effects on the rest of the body.

Loading and bone fragility

Data from retrospective and prospective observational and case-control studies suggest that activity is associated with reduced fracture risk, but consistently replicated bias may be responsible for this desired endpoint. Exercise during growth is likely to build a larger and stronger skeleton. However, cessation of exercise may erode the benefits. Modeling changes produced by exercise during growth may be permanent; remodeling changes may not be. Exercise during adulthood produces small increments in BMD or may prevent bone loss. Absence of evidence is not evidence of absence of effect, but the null hypothesis that exercise has no effect on fracture rates in old age cannot be rejected by any published data. Proof requires demonstration of a reduction in spine and hip fractures in well-designed and well-executed prospective randomized studies; none exists. Blinded studies cannot be done, but open trials can and should be done.

Current knowledge about physiotherapeutic strategies in osteoporosis prevention and treatment

In treating patients with osteoporosis, one option in physiotherapy is to comply with given physical norms by using physical stimuli to influence biological functions and structures (bone, muscle) for adaptation, stimulation, and regeneration. Serial physical stimuli can also be used for interventions and actions to minimise pain perception by means of biopsychosocial influence. In osteoporosis, physiotherapy has to be rated on a par with pharmacotherapy with respect to prevention, cure, and rehabilitation. Generally, two different aims can be defined: (1) those which can be achieved with physical therapy alone, such as structural improvement of the existing and pharmacologically increased bone tissue, slowing down of round-back formation, and fall prophylaxis and (2) those which can be achieved with physiotherapy and pharmacotherapy, such as effective pain relief and increased bone density. Regulation and normalisation of physical capacities with an aim towards maintenance and economisation of functions and improvement in abilities call for a skillful and case-specific use of physiotherapy.

Association between exercise and pubertal BMD is modulated by estrogen receptor alpha genotype

Genetic and environmental factors contribute to bone mass, but the ways they interact remain poorly understood. This study of 245 pre- and early pubertal girls found that the PvuII polymorphism in the ER-alpha gene modulates the effect of exercise on BMD at loaded bone sites.

INTRODUCTION

Impaired achievement of bone mass at puberty is an important risk factor for the development of osteoporosis in later life. Genetic, as well as environmental, factors contribute to bone mass, but the ways they interact with each other remain poorly understood.

MATERIALS AND METHODS

We investigated the interaction between a PvuII polymorphism at the ER-alpha gene and physical activity (PA) on the modulation of bone mass and geometry in 245 10- to 13-year-old pre- and early pubertal Finnish girls. Level of PA was assessed using a questionnaire. Bone properties were measured using DXA and pQCT. The analyses were controlled for the effects of Tanner stage and body size index.

RESULTS

Girls with heterozygote ER-alpha genotype (Pp) and high PA had significantly higher bone mass and BMD, as well as thicker cortex, at loaded bone sites than their low-PA counterparts. No differences were found in bone properties of the distal radius, which is not a weight-bearing bone. Bone properties did not differ in either homozygote groups (PP and pp) regardless of the PA level.

CONCLUSIONS

These findings suggest that the PvuII polymorphism in the ER-alpha gene may modulate the effect of exercise on BMD at loaded bone sites. The heterozygotes may benefit most from the effect of exercise, whereas neither of the homozygote groups received any significant improvement from high PA. Furthermore, high PA may hide the genetic influence on bone. Indeed, it seems that one may compensate one's less favorable Pp genotype by increasing leisure PA at early puberty.

Has exercise an antifracture efficacy in women?

Exercise in girls during growth seems to confer a high peak bone mineral density (BMD). Exercise in adulthood, in the peri- and postmenopausal period, and in old age prevents bone loss or increases BMD with a magnitude of minor biological significance. However, these changes must be regarded as beneficial compared to the age-related bone loss, which inevitably will occur if no interventions are implemented. Prospective intervention studies also suggest that exercise improves muscle strength, coordination and balance, even in elderly women, all of which are improvements with a potential of reducing the number of falls. A randomised, controlled, prospective, blinded study (the only study design that tests a hypothesis) of exercise with fracture as end point is extremely difficult to conduct, due to the large sample sizes needed. At present, no such studies exist. Retrospective and prospective observational and case-control studies suggest that physical activity in women is associated with reduced fracture risk. This may be correct, but we must never forget that a consistently replicated sampling bias may produce the same outcome. The Achilles heel of exercise is the reduction or the cessation of physical activity, which commonly occurs among middle-aged women when family and work demands reduce the time available for exercise. A higher BMD or improvement in muscle size and muscle strength achieved by exercise during adolescence seems to be eroded on retirement, leaving virtually no remaining benefits in old age, the period when fragility fractures begin to be a problem of increasing magnitude. However, recreational activities seem to maintain some of the musculo-skeletal benefits, but to date we do not know the level of activity needed to retain these benefits. Dose-response relationships need to be quantified, as also the effects on bone size, shape and architecture. Another essential question that we must address is how many fewer fractures will be the result of a community-based exercise campaign. Will efforts by the community to encourage a higher level of physical exercise, with the aim of reducing bone fractures, be cost-effective? The higher level of proof, suggesting that exercise does reduce fragility fractures and thus reduces the total cost for the society, must come from well-designed and well-executed, prospective, randomised, controlled trials. The responsibility of executing these studies lies in the hands of both researchers and the community.

Effect of impact load and active load on bone metabolism and body composition of adolescent athletes

PURPOSE

It is unclear whether adolescents involved in nonweight-bearing activities experience a delay in bone growth acquisition and sexual maturation. The purpose of this study was to compare bone mineral density (BMD), body composition, hormonal profile, and bone biochemical markers of adolescent athletes active in sports involved in impact load sports with those participating in active load sports.

METHODS

Forty-five male Caucasian athletes aged 12--18 yr were divided into two groups according to type of skeleton loading, impact (N = 18), or active (N = 27). Twenty-four male Caucasian adolescents (12--18 yr) served as controls and only performed the activities included in their physical education classes. All subjects were assessed for bone mass, body composition, and bone age by dual x-ray absorptiometry (DXA). Serum calcium (Ca), phosphorus (P), bone-specific alkaline phosphatase (BAP), total testosterone, FSH, LH, urinary calcium to creatinine ratio (Ca/Cr), and urinary deoxypyridinoline crosslinks to creatinine ratio (DPD/Cr) were measured.

RESULTS

The impact load group presented the highest BMD among the three groups for all studied sites. Lean mass and absolute weight were correlated with all of the bone mass measurements. BAP levels were significantly higher and testosterone levels significantly lower in the active load group compared with the impact group.

CONCLUSION

High-impact load exercises have a beneficial effect on bone mass in male adolescents. There is also a positive correlation of weight and body composition with BMD. However, further longitudinal studies are necessary to determine whether there is a delay in bone growth acquisition among adolescents involved in a nonweight-bearing exercise regimen and its association with sex hormones.

Differential influence of physical activity on lumbar spine and femoral neck bone mineral density in the elderly population

This study investigates the relationship between lifetime physical activity and bone mineral density (BMD) at various sites in 129 healthy men and women aged 72.1 +/- 6.5 years. BMD was measured by dual energy x-ray absorptiometry, and physical activity was assessed by using the QUANTAP system (Quantification de l'Activité Physique), a standardized and structured computer-assisted interview tool designed to assess lifetime physical activity. Linear regression models controlling for age, gender, height, body mass, lean mass, and smoking habits were performed. Higher levels of sporting activity during youth were associated with greater lumbar spine BMD ( p < .001). Similarly, femoral neck BMD was greatest in subjects who reported regularly taking part in sports over the previous 20 years ( p <. 05) and during their whole lifetime ( p < 0.05). Sporting activity at the time of bone mass development increases subsequent lumbar spine BMD, and more recent sporting activity contributes to the preservation of femoral neck BMD. These results suggest that physical activity has a differential influence on BMD at different sites and at different ages, possibly related to the processes of bone construction and bone aging taking place at the time.

The prepubertal years: a uniquely opportune stage of growth when the skeleton is most responsive to exercise?

The growing years may be the most opportune time in life for exercise to result in large increases in bone density, enough to reduce the risk of fracture late in life. However, it is not known if there is an 'optimal' time during growth when the skeleton is most responsive to exercise. Comparing the osteotrophic response to exercise between pre- and peripubertal children is complex because: (i) the development of the skeleton within each stage of puberty is characterised by differing temporal patterns of growth in bone size and mass; (ii) the hormonal regulation of the skeleton is unique to each stage of puberty; and (iii) it is difficult to equate the relative mechanical load placed on the prepubertal compared with the pubertal skeleton. There are sound biological bases for the hypotheses being proposed for both the pre- and peripubertal years being the time when the skeleton is most responsive to exercise; that is, exercise may enhance bone formation in a synergistic fashion in the presence of growth hormone (prepubertal years) or sex steroids (peripubertal years). The paucity of data and the complex methodology make it difficult to draw conclusions as to the most opportune time during growth when exercise may lead to the greatest osteotrophic response. The limited data available support the notion that the prepubertal years may be the most opportune time, due to increases in bone density and periosteal expansion of cortical bone.

Mechanical strain stimulates nitric oxide production by rapid activation of endothelial nitric oxide synthase in osteocytes

Previous studies have indicated that physiological levels of dynamic mechanical strain produce rapid increases in nitric oxide (NO) release from rat ulna explants and primary cultures of osteoblast-like cells and embryonic chick osteocytes derived from long bones. To establish the mechanism by which loading-induced NO production may be regulated, we have examined: nitric oxide synthase (NOS) isoform mRNA and protein expression, the effect of mechanical loading in vivo on NOS mRNA expression, and the effect of mechanical strain on NO production by bone cells in culture. Using Northern blot analyses, in situ hybridization, and immunocytochemistry we have established that the predominant NOS isoform expressed in rat long bone periosteal osteoblasts and in a distinct population of cortical bone osteocytes is the endothelial form of NOS (eNOS), with little or no expression of the inducible NOS or neuronal NOS isoforms. In contrast, in non-load-bearing calvariae there are no detectable levels of eNOS in osteocytes and little in osteoblasts. Consistent with these observations, ulnar explants release NO rapidly in response to loading in vitro, presumably through the activation of eNOS, whereas calvarial explants do not. The relative contribution of different bone cells to these rapid increases in strain-induced NO release was established by assessment of medium nitrite (stable NO metabolite) concentration, which showed that purified populations of osteocytes produce significantly greater quantities of NO per cell in response to mechanical strain than osteoblast-like cells derived from the same bones. Using Northern blot hybridization, we have also shown that neither a single nor five consecutive daily periods of in vivo mechanical loading produced any significant effect on different NOS isoform mRNA expression in rat ulnae. In conclusion, our results indicate that eNOS is the prevailing isoform expressed by cells of the osteoblast/osteocyte lineage and that strain produces increases in the activity of eNOS without apparently altering the levels of eNOS mRNA.

Aerobic exercise and lumbar spine bone mineral density in postmenopausal women: a meta-analysis

PURPOSE

To use the meta-analytic approach to examine the effects of aerobic exercise on lumbar spine bone mineral density in postmenopausal women.

DATA SOURCES

Studies were retrieved from computer searches (MEDLINE, Current Contents) as well as cross-referencing from the bibliographies of retrieved studies and review articles.

STUDY SELECTION

A total of 17 effect sizes consisting of 330 subjects (192 exercise, 138 nonexercise) were included from the 10 studies that met the criteria for inclusion: (1) aerobic activity as the only exercise intervention, (2) postmenopausal women as subjects, (3) comparative nonexercise group included, (4) changes in lumbar spine bone mineral density reported, (5) studies published in English-language journals between January 1975 and December 1994.

DATA EXTRACTION

The primary outcome measure of interest was the treatment effect delta3, defined as the percent change in lumbar spine bone mineral density, calculated by subtracting the percent change in the exercise group from the percent change in the nonexercise group.

RESULTS

Using a fixed effects model, bootstrap analysis (10,000 replications) showed that significant changes in lumbar spine bone mineral density occurred (mean +/- SD = 2.83 +/- 0.77%, 95% confidence interval (CI) = 1.33 to 4.35%). This overall average increase was caused primarily by the loss of lumbar spine bone mineral density in the nonexercise group relative to the exercise group (mean +/- SD, exercise = .32 +/- 2.46%, 95% CI = -0.94 to 1.58; nonexercise = -2.51 +/- 2.69%, 95% CI = -4.60 to -0.96).

CONCLUSION

The results of this meta-analysis suggest that aerobic exercise helps to maintain lumbar spine bone mineral density in postmenopausal women.

Abnormalities in skeletal growth in children with juvenile rheumatoid arthritis

A review of the acquisition of peak skeletal mass in normal children and studies that have been reported for children with JRA lead to the following tentative conclusions: (1) The appendicular skeleton is predominantly the overall status of skeletal mineralization; (2) a failure to develop adequate bone mineralization is virtually universal in children with JRA and is characterized by a failure of bone formation. A failure to undergo the normal increase in bone mass during puberty is common in children with JRA and markedly decreases their potential to achieve an adequate peak skeletal mass; (3) the onset of accelerated skeletal maturation with puberty is a critical period of potential intervention in JRA. Conversely, therapeutic interventions later during adolescence offer less promise of reversal of inadequate bone mineralization; and (4) the most important therapeutic maneuver is likely to be control of the inflammation process, although there is hope, at present unsubstantiated, that supplemental dietary calcium and vitamin D, and normalization of physical activity, many lead to some "catch-up" mineralization.

Determinants of peak bone mass in Chinese women aged 21-40 years. III. Physical activity and bone mineral density

Previous studies on the relation between moderate physical activity and bone mass have observed conflicting results. Many of these studies have not dissociated the role of physical activity by age groups and in relation to the period of peak bone mass formation. Our cross-sectional analysis of the baseline data of a longitudinal study of 273 women aged 21-40 attempted to evaluate the role of moderate physical activity on bone mass around the period of peak bone mass attainment. The analyses were carried out separately for the two age groups--21-30 and 31-40--and had also taken into account the effects of age, dietary calcium intake, and lean body mass on bone mineral density (BMD). The total metabolic equivalent values (MET) of leisure time physical activity was based on the MET values for each activity and the reported time spent on each activity in the past year. The results indicated that among the younger group of women, high level of leisure time physical activity was associated with higher bone mass at both the spine and the hip. Additive effects of physical activity and dietary calcium intake on the spine and the hip BMD were observed. Together with age and lean body mass, physical activity and dietary calcium intake accounted for 19% of the variances of bone mineral at the spine and 9-11% at the hip. Among women aged 31-40, presumably after the peak bone mass formation, lean body mass as well as fat mass have independent strong association with BMD. Physical activity was not associated with bone mass in this age group.

Physical activity and predisposition for hip fractures: a review

Studies on the association between physical activity and hip fractures are reviewed. All the studies, which comprise four follow-up studies, one nested case-control study and 17 case-control studies, suggest a protective effect of physical activity with regard to hip fractures. The association is strong and consistent with physical activity in leisure, weaker with respect to physical activity at work. The association is present for physical activity from childhood to adult age, and it is consistent in study populations from the USA, Australia, Asia and Northern and Southern Europe, in spite of very different hip fractures incidences in these populations. The magnitude of the association is difficult to assess because of varying criteria for exposure, but to be among the physically active seems to reduce the risk of later hip fracture by up to 50%. It seems that even daily chores, such as climbing stairs and walking, protect against hip fracture.

Expression of tenascin-C in bones responding to mechanical load

A number of early biochemical responses of bone cells to mechanical loading have been identified, but the full sequence of events from the sensing of strain to the formation of new bone is poorly characterized. Extracellular matrix proteins can modulate cell behavior and would be ideal molecules to amplify the early response to loading. The extracellular matrix protein, tenascin-C, supports differentiation of cultured osteoblast-like cells. The current study was carried out to investigate whether expression patterns of tenascin-C in loaded bones support a role for this protein as a mediator of the osteoregulatory response to loading. Tenascin-C expression was investigated by Northern blot analysis in rat ulnae subjected to an established noninvasive loading regimen engendering physiological strain levels. RNA extracted from loaded compared with contralateral control bones 6 h after loading showed a significant increase in tenascin-C transcript expression. The presence of tenascin-C was investigated by immunohistochemistry in bones of animals killed 3, 5, or 15 days after the initiation of daily loading. In animals killed at 3 or 5 days, periosteal surfaces undergoing load-induced reversal from resorption to formation showed enhanced tenascin-C staining. In animals killed at 15 days, the bone formed in response to loading was clearly demarcated from old bone by strong tenascin-C staining of reversal lines. Within this new bone, tenascin-C staining was seen in the lacunae of older but not more recently embedded osteocytes. The results presented here indicate that tenascin-C expression by bone cells is enhanced in the early osteogenic response to loading. This may indicate that tenascin-C acts as a mediator of the mechanically adaptive response.

Bone mineralization and bone mineral metabolism in children with juvenile rheumatoid arthritis

OBJECTIVE

To identify mechanisms of the osteopenia associated with juvenile rheumatoid arthritis (JRA) by determining parameters of bone mineralization, and bone mineral content and density (BMC and BMD), in children with JRA.

METHODS

BMC and BMD were measured by dual x-ray absorptiometry in 41 children with JRA and 62 healthy children. Serum samples were analyzed for concentrations of minerals, vitamin D, parathyroid hormone, osteocalcin, bone-specific alkaline phosphatase (BAP), procollagen I carboxy-terminal propeptide, and tartrate-resistant acid phosphatase (TRAP), and urinary excretion of deoxypyridinoline crosslinks and calcium.

RESULTS

BMD was decreased in all sites in JRA patients. BMD, corrected for age, height, weight, and bone area, was decreased at cortical bone sites (1/3 radius, upper and lower extremities, and whole body). Low concentrations of osteocalcin and BAP suggested reduced bone formation, and low TRAP levels suggested decreased resorption. Clinical scales of disease severity were negatively correlated with measures of bone mass. Laboratory markers of disease severity were highly correlated with decreases in markers of bone formation, but not with those of resorption. Although laboratory findings were similar for children with oligoarticular and polyarticular disease, differences in bone mass were greater in children with polyarticular disease.

CONCLUSION

These data suggest an association between decreased bone mineralization in JRA and low bone formation that is related to disease severity. Efforts to stimulate bone formation, therefore, need to be considered clinically in prepubertal children with active JRA.

Biochemical markers of bone metabolism during distance running in healthy, regularly exercising men and women

The purpose of the present study was to evaluate the effects of long distance running on bone metabolism, using the biochemical markers ICTP (the carboxyterminal cross-linked telopeptide of type I collagen), PICP (the carboxyterminal propeptide of type I procollagen), osteocalcin and bALP (bone specific alkaline phosphatase) as well as parathyroid hormone (PTH) and serum calcium. Twenty healthy, regularly exercising individuals, 10 women and 10 men, participated in a running competition. The mean age was 38 (range 22-55) and 39 (range 22-53) years respectively, the performed distance 15 (range 5-30) and 28 (range 15-30) km respectively, with a speed of 5:30, 5:02 per kilometer respectively. Fasting blood samples were drawn in the morning the day before the race, and also the day after and two days after. A decrease of PICP concentrations among women was evident the day after the competition (from 170 +/- 17 micrograms/l to 158 +/- 17 micrograms/l) which returned to pre-exercise levels two days after the race (167 +/- 19 micrograms/l). Furthermore, a decrease of osteocalcin could be seen in the men one day after the exercise (from 12.1 +/- 1.1 micrograms/l to 10.3 +/- 1.1 micrograms/l). In the men, there was also an increase of ICTP concentrations two days after (3.98 +/- 0.35 micrograms/l) this long-term and demanding exercise, when compared with pre-exercise levels (3.67 +/- 0.28). One single bout of long-term, exhaustive running exercise in well-trained men and women seems to induce a temporary inhibition of bone formation as well as a stimulation of bone resorption.

Bone mineral metabolism in children with juvenile rheumatoid arthritis

Osteopenia has emerged as a major determinant of the outcome of children with juvenile rheumatoid arthritis. Although vertebral compression fractures and fractures of long bones were recognized historically as important clinical developments in the course of disease, a decrease in skeletal mass could only be quantitated and documented early in disease by the recent introduction of bone absorptiometry. This article is limited to recent data from studies on osteopenia in juvenile rheumatoid arthritis and suggests directions of future research that have relevance to current unanswered questions in prevention or management.