High-impact loading training induces bone hyperresorption activity in young elite female gymnasts

Health Effects of Wrist-Loading Sports During Youth: A Systematic Literature Review

BACKGROUND

The benefits and risks of performing popular wrist-loading sports at a young age have not been investigated systematically. We aimed to evaluate positive and negative long-term wrist-related health effects of sports performance requiring repetitive wrist loading during youth.

METHODS

Six databases were searched for cohort and cross-sectional studies. Three investigators selected studies evaluating quantitatively measured health effects of upper extremities in athletes practicing wrist-loading sports (gymnastics, tennis, volleyball, field hockey, rowing, and judo) for minimally 4 months before the age of 18.

RESULTS

A total of 23 studies with 5 outcome measures, nearly all of moderate to good quality, were eligible for inclusion. Bone mineral density and bone mineral content were higher in athletes compared with controls and in tennis players' dominant arm. Mixed results were found for ulnar variance in gymnasts. Handgrip strength was greater in tennis players' dominant arm and in experienced gymnasts.

CONCLUSIONS

Wrist-loading sports performance during youth can promote bone strength in wrists and dominant handgrip strength, but evidence on the lasting of these effects and on prevalence of wrist joint degeneration in former young athletes is limited. For better counseling of young athletes and their parents, future studies with increased comparability are essential, for which recommendations are provided.

Physical activity may be a potent regulator of bone turnover biomarkers in healthy girls during preadolescence

This study investigated the effects of different levels of habitual physical activity (PA) assessed by pedometry on bone turnover markers of preadolescent girls according to a cross-sectional experimental design. Sixty prepubertal girls of similar chronological age, bone age, maturity level, and nutritional status were assigned to a low PA (LPA; n = 25), a moderate PA (MPA; n = 17), or a high PA (HPA; n = 18) group. Dual-energy X-ray absorptiometry was used to measure areal bone mineral density (BMD) and bone mineral content (BMC) of the lumbar spine (L2-L4) and dominant hip (femoral neck and trochanter). Blood was collected for the measurement of alkaline phosphatase (ALP), bone-specific ALP (BSAP), procollagen type I N-terminal propeptide (PINP), C-terminal telopeptide of collagen I (CTX), parathyroid hormone (PTH), osteocalcin, thyroid-stimulating hormone, estradiol, testosterone, luteinizing hormone, and follicle-stimulating hormone concentrations. ANOVA revealed that the HPA group (18,695 ± 1244 steps per day) had a lower daily energy intake and body mass than the MPA group (10,774 ± 521 steps per day) and the LPA group (7633 ± 1099 steps per day). The HPA group had higher (P < 0.05) lumbar and hip BMD and hip BMC than the LPA group and higher (P < 0.05) lumbar BMD than the MPA group. The MPA group had higher (P < 0.05) hip BMC than the LPA group. The HPA group had greater (P < 0.05) values of BSAP, PINP, and ALP and lower (P < 0.05) values of PTH and CTX than the LPA group but not the MPA group. A partial correlation analysis (adjusted for body mass index) revealed a positive correlation of steps per day with BMD and BSAP concentration and a negative correlation with PTH and CTX concentration. In conclusion, PA increases BMD and BMC of premenarcheal girls by favoring bone formation over bone resorption.

Endocrine disorders in adolescent and young female athletes: impact on growth, menstrual cycles, and bone mass acquisition

CONTEXT

Puberty is a crucial period of dramatic hormonal changes, accelerated growth, attainment of reproductive capacity, and acquisition of peak bone mass. Participation in recreational physical activity is widely acknowledged to provide significant health benefits in this period. Conversely, intense training imposes several constraints, such as training stress and maintenance of very low body fat to maximize performance. Adolescent female athletes are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function. The "adaptive" changes in the hypothalamic-pituitary-gonadal, -adrenal, and somatotropic axes and the secretory role of the adipose tissue are reviewed, as are their effects on growth, menstrual cycles, and bone mass acquisition.

DESIGN

A systematic search on Medline between 1990 and 2013 was conducted using the following terms: "intense training," "physical activity," or "exercise" combined with "hormone," "endocrine," and "girls," "women," or "elite female athletes." All articles reporting on the endocrine changes related to intense training and their potential implications for growth, menstrual cycles, and bone mass acquisition were considered.

RESULTS AND CONCLUSION

Young female athletes present a high prevalence of menstrual disorders, including delayed menarche, oligomenorrhea, and amenorrhea, characterized by a high degree of variability according to the type of sport. Exercise-related reproductive dysfunction may have consequences for growth velocity and peak bone mass acquisition. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine system may orient research to develop innovative strategies (ie, based on nutritional or pharmacological approaches and individualized modalities of training and competition) to improve the medical care of these adolescents and protect their reproductive function.

Effects of physical activity on bone remodeling

Physical exercise is recommended to improve bone mass in growing children and decrease bone loss in elderly men and women. However, the specific mechanisms by which exercise influences bone metabolism are still not thoroughly understood. The effect of physical activity on the skeleton is generally evaluated by dual-energy x-ray absorptiometry, which measures bone mineral density. However, a relatively long period is needed to detect even a minor variation in bone mineral density with this technique, limiting its usefulness. Bone biochemical markers that reflect the cellular activities of bone formation and resorption are thus also useful tools, both to monitor the acute effects of exercise on bone remodeling and to investigate the mechanisms of exercise-induced changes in bone mass. This article describes the effects of physical activity on bone remodeling in various types of population. The comparison of sedentary individuals and athletes with many years of high-volume sports practice, for example, has clarified some of the long-term effects of exercise. Moreover, the acute variation in bone cell activities after brief exercise or a training program is here examined. The interpretation of results is difficult, however, because of the many parameters, such as age, that are involved. The various populations are therefore categorized to reflect the biological factors implicated in the modulation of bone marker response during exercise.

High impact exercise is more beneficial than dietary calcium for building bone strength in the growing rat skeleton

The benefits of impact exercise and dietary calcium on bone development are controversial. We used inbred rats under highly controlled conditions to test the independent and combined effects of impact exercise and physiological levels of calcium intakes on the growing skeleton. Forty growing F-344 female rats were fed diets containing either 100% (Ca+; 0.5% Ca) or 40% (Ca(-); 0.2% Ca) of their calcium requirements. Half of each dietary group was subjected to either 10 impacts per day from 45 cm freefall drops (Impact+), or no impact (Impact(-)). All rats received a free choice of physical activity period daily. After 8 weeks, the mechanical strength, volumetric density, geometry, and microarchitecture of their ulnae were measured. Body weight and bone length did not differ among groups. On both diets, freefall impact resulted in greater bone strength, cross-sectional moments of inertia, and endosteal and periosteal circumferences in the shaft. Only Ca+ resulted in greater shaft volumetric bone mineral density (vBMD) but that did not affect shaft breaking strength. In the bone ends, both Impact+ and Ca+ positively affected density and structure of both cortical and trabecular bone but the effects of Impact+ were more pervasive. In the proximal end, Impact+ resulted in greater bone volume fraction (BV/TV) in the trabecular bone due to greater trabecular thickness, and cortical thickness was greater due to a smaller endosteal circumference. Impact+ exerted a compensatory effect on vBMD and BV/TV in Ca(-) rats at the proximal site. In Impact(-) rats only, Ca+ resulted in greater total and cortical vBMD and BV/TV in the proximal ulna. Impact+ and Ca+ exerted additive effects on cortical bone area (BA) in the proximal ulna and on total BA, periosteal circumference, and trabecular vBMD in the distal ulna. In conclusion, impact exercise was more beneficial than adequate dietary calcium to growing bones, although sufficient dietary calcium was beneficial in rats not subjected to impact exercise.

Calcium and Exercise Affect the Growing Skeleton

Adequate dietary calcium and bone-stimulating exercise during growth are known to affect skeletal development, but the combined effects of dietary calcium and osteogenic exercise have received scant attention. Animal research has showed a compensatory effect of impact loading on calcium-deprived bones, while various human studies have suggested compensatory, additive, or possibly synergistic effects in certain skeletal locations. Current evidence suggests that the best strategy for strong bones by the end of childhood may be either high-impact exercise with a moderate or greater calcium intake or a combination of moderate-impact exercise and adequate calcium during growth.

Bone mineral density differences between adolescent dancers and non-exercising adolescent females

STUDY OBJECTIVE

To compare the bone mineral density (BMD) of the axial and appendicular skeleton between regularly exercising collegiate dancers and age matched non-exercising young females between the age of 17 and 19 to assess the impact of weight-bearing exercises and menstrual status on BMD.

DESIGN

Prospective observational cohort.

SETTING

Sports clinic in a collegiate school of dance and a hospital-based adolescent clinic.

PARTICIPANTS

The adolescent dancers consisted of full-time collegiate dance students from a tertiary Performing Arts Institute (n = 35). The non-exercising controls consisted of eumenorrhoeic patients of the same age presenting to the Adolescent Clinic (n = 35).

INTERVENTIONS

All subjects had a full hormonal profile, bio-impedance estimation of body fat, and dual energy X-ray absorptiometry and quantitative peripheral CT scans (pQCT) to determine bone density.

MAIN OUTCOME MEASURES

Comparison of the mean bone mineral density in the axial and appendicular skeleton between the two groups.

RESULTS

The incidence of oligo/amenorrhoea in the dancers was 20%. The lumbar spine BMD (1.006 g/cm(2) vs. 0.938, P = 0.048) and hip BMD (neck of femur 0.978 g/cm(2) vs. 0.838, P < 0.001; Ward's triangle 0.816 g/cm(2) vs. 0.720, P = 0.003; trochanter 0.777 g/cm(2) vs. 0.682; P < 0.001) were significantly higher in the eumenorrhoeic dancers as compared to controls. The radial BMD as measured by pQCT did not differ between the two groups, but the core trabecular tibial BMD was also higher in the dancers (321 mg/cm(3) vs. 286, P = 0.006). When only oligo/amenorrhoeic dancers (n = 7) were compared with the controls, the same differences in BMD values were no longer observed.

CONCLUSION

Young women undergoing regular intensive weight-bearing exercises as in the collegiate dancers here studied have higher BMD in the axial and appendicular skeleton as compared to non-exercising females of the same age if they remain eumenorrhoeic during their training. This advantage was apparently lost when they developed oligo/amenorrhoea.

Estimation of Total-Body Skeletal Muscle Mass in Children and Adolescents

PURPOSE

The estimation of total-body skeletal muscle mass (SMM) has been predicted in healthy adults using anthropometric measurements and urine creatinine excretion. SMM measurement is compulsory to evaluate exercise performance and the influence of physical training on muscle mass. However, there is a lack of information on children and adolescents when quantifying appendicular skeletal muscle mass.

METHODS

Thirty-nine Caucasian children and adolescents (male and female, 7-16 yr old) and 20 adults (men and women, 20-24 yr old) were tested for total-body SMM using dual-energy x-ray absorptiometry measurement (DEXA), anthropometric measurements (ANTHR), and urine creatinine (UCrn) determination. Skinfold thickness and circumference were measured at mid-arm (CAG), mid-thigh (CTG), and mid-calf (CCG) and the skin-corrected circumferences (cm), together with height (Ht; m), age (yr), and sex (0 for female, 1 for male). The UCrn excretion (g.24 h(-1)) was also determined in all subjects. The ANTHR and UCrn measurements were then compared with DEXA as reference value.

RESULTS

The multiple linear regression from anthropometric measurements gave the following equation to evaluate the total-body skeletal muscle mass (SMM) in children and adolescents: SMM (kg) = Ht x [(0.0064 x CAG) + (0.0032 x CTG) + (0.0015 x CCG)(2)] + (2.56 x sex) + (0.136 x age). The prediction of SMM from a 24-h urine collection was obtained with the following equation: SMM (kg) = (10.62 x Crn) + 6.63. The correlation coefficient (r(2)) was 0.966 and 0.710 for the anthropometric and creatinine methods, respectively (P < 0.001).

CONCLUSION

Besides DEXA technique, the determination of total-body skeletal muscle mass in children and adolescents can be highly validated with satisfactory confidence by simple anthropometric measurements or 24-h urine creatinine excretion.

Significant exercise-related changes in the serum levels of two biomarkers of collagen metabolism in young horses

OBJECTIVE

To identify metabolic biomarkers that can be evaluated in serum for monitoring the effects of exercise on skeletal development in mammals.

DESIGN

Sera of foals from three groups (box-stall rest, pasture and training) were serially collected over the first 5 months of life and assayed for eight biomarkers of cartilage and bone metabolism. Sub-populations from each group were sampled for an additional 6 months of identical exercise.

RESULTS

When expressed as a percentage of baseline values, lower serum levels of the carboxy-terminal propeptides of type II collagen (CPII), and higher serum levels of the cross-linked telopeptide fragments of degraded type I collagen (CTx1) were found in the trained foals compared to the other groups. Significant differences disappeared in those foals sampled during an additional 6 months of identical exercise. The most significant correlations were between serum biomarkers of bone metabolism, being positive between anabolic markers and negative between anabolic and catabolic markers. Serum levels of CTx1 and CPII significantly increased with age in all groups throughout the study.

CONCLUSIONS

We have identified two markers of collagen metabolism, CPII and CTx1, as potential serum indicators of the exercise effects on the developing skeletal system in horses. Forced exercise during the first months postpartum appeared to have a negative effect on collagen turnover when compared to levels in pastured foals. Routine monitoring of collagen biomarkers in sera of exercising young mammals may allow for the early detection of abnormalities in skeletal tissue metabolism and for subsequent intervention before permanent damage occurs.

Semi-automated evaluation of the cortico-medullar index on radius radiographs: a study in prepubertal girls

The aim of the study was to validate a non-invasive method allowing a semi-automatic cortico-medullar index (CMI) computation from standard radiographs. Fifty-five radiographs of the non-dominant radius of prepubertal girls (aged 10.12+/-1.47 years) were scanned (100 microm scanning resolution) by the same observer. To detect the grey level peaks, we used the Deriche's recursive filter applied to the grey level gradients and we defined the cortical areas by thresholding (iterative contour detection). The CMI was calculated as cortical areas divided by the total bone area. The reproducibility was tested through the analysis of ten radiographs scanned twice, on 5, 10, 15, 20, 30 and 40 lines at each side of a reference line located at the distal third part of the radius. We used the root mean square coefficient of variation (RMS-CV) as verification. Dual-Energy X-ray (DXA) was used for densitometry measurements of the whole body, and non dominant radius (mid-, distal third and ultra distal). The result attaining the best reproducibility concerned the 15-line position (Mean CMI=0.58+/-0.005 with a 1.36% RMS-CV). CMI correlated significantly with Bone Mineral Density (BMD) (r=0.40, 0.33 and 0.50, P<0.01, respectively, at the whole body, mid- and third distal of the radius), Bone Mineral Content (BMC) (r=0.32, 0.36, 0.34 and 0.35, respectively, at the whole body (P=0.01), mid- (P=0.007), third distal (P=0.01) and ultra distal of the radius (P=0.01)) but not with BMD at the ultra distal of the radius (r=-0.01, P=0.9). This semi-automated new method has been easily implemented, reproducible, and therefore, could be useful tool for the bone CMI computation.