Effects of high-impact exercise on ultrasonic and biochemical indices of skeletal status: A prospective study in young male gymnasts

A kinetic and kinematic comparison of the two-footed and step-out back handsprings on the balance beam

The back handspring is one of the most commonly performed skills on the balance beam in women's gymnastics. Despite this, quantitative research on the beam has often been overlooked. This study aimed to investigate the kinetic and kinematic variables during the performance of two back handspring techniques on the beam: the back handspring with two footed landing and the back handspring step-out. A modified balance beam was fixed to a force plate with an isolated mat for landing to allow analysis of the take-off and hand contact phases. Kinetic and kinematic data were recorded for twelve gymnasts performing both techniques. No statistically significant differences between techniques were found during take-off. However, average peak vertical and horizontal ground reaction forces (4.1 bodyweights ± 1.1 BW, and 0.7 BW ± 0.2 BW, respectively) were higher and time to peak force shorter during the hand contact phase for the two footed variant. A more vertical trajectory, along with a greater hand contact ground reaction force were found in comparison to the back handspring performed on the floor. These results highlight the need for more specific investigation to understand the factors which could contribute to reducing the load faced during balance beam performance.

Short-termed changes in quantitative ultrasound estimated bone density among young men in an 18-weeks follow-up during their basic training for the Swiss Armed Forces

Background

Quantitative Ultrasound (QUS) methods have been widely used to assess estimated bone density. This study aimed to assess changes in estimated bone density in association with changes in body composition, physical activity, and anthropometry.

Methods

We examined changes in anthropometry, body composition, and physical activity associated with changes in estimated bone mineral density (measured using quantitative ultrasound with a heel ultrasound device indicating broadband ultrasound attenuation BUA and speed of sound SOS) in a follow-up sample of n = 73 young men at the beginning and again 18 weeks later at the end of basic military training.

Results

At the end of the basic training, the subjects were on average significantly heavier (+1.0%), slightly taller (+0.5%) and had a higher fat mass (+6.6%) and grip strength (+8.6%). A significant decrease in mean physical activity (-49.5%) and mean estimated bone density calculated with BUA (-7.5%) was observed in the paired t-test. The results of the multivariable linear regressions (backward selection) show that changes in skeletal muscle mass (delta = 2nd measurement minus 1st measurement) have negative and body weight (delta) have positive association with the speed of sound SOS (delta), while fat mass (delta) and physical activity (delta) had the strongest negative associations with estimated bone mineral density (delta). In particular, we found a negative association between fat mass (delta) and estimated bone mineral density (delta, estimated with BUA).

Conclusion

Our study suggests that estimated bone density from the calcaneus can change within a few months even in young and mostly healthy individuals, depending upon physical activity levels and other co-factors. Further studies including other troop types as control groups as well as on women should follow in order to investigate this public health relevant topic in more depth. To what extent the estimated bone density measurement with quantitative ultrasound is clinically relevant needs to be investigated in further studies.

Physical Activity in Late Prepuberty and Early Puberty Is Associated With High Bone Formation and Low Bone Resorption

Background

Physical activity (PA) increases bone mass, especially in late prepuberty and early puberty, but it remains unclear if and how PA affects both bone formation and bone resorption.

Materials and Methods

We included 191 boys and 158 girls aged 7.7 ± 0.6 (mean ± SD) in a population-based PA intervention study. The intervention group (123 boys and 94 girls) received daily physical education (PE) in school (40 min/day; 200 min/week) from study start and during the nine compulsory school years in Sweden. The controls (68 boys and 64 girls) received the national standard of 1–2 classes PE/week (60 min/week). During the intervention, blood samples were collected at ages 9.9 ± 0.6 (n = 172; all in Tanner stages 1–2) and 14.8 ± 0.8 (n = 146; all in Tanner stages 3–5) and after termination of the intervention at age 18.8 ± 0.3 (n = 93; all in Tanner stage 5) and 23.5 ± 0.7 (n = 152). In serum, we analyzed bone formation markers [bone-specific alkaline phosphatase (bALP), osteocalcin (OC), and N-terminal propeptide of collagen type 1 (PINP)] and bone resorption markers [C-terminal telopeptide cross links (CTX) and tartrate-resistant acid phosphatase (TRAcP 5b)]. Linear regression was used to compare age and sex-adjusted mean differences between intervention children and controls in these markers.

Results

Two years after the intervention was initiated (at Tanner stages 1–2), we found higher serum levels of bALP and OC, and lower serum levels of TRAcP 5b in the intervention compared with the control group. The mean difference (95% CI) was for bALP: 13.7 (2.1, 25.3) μg/L, OC: 9.1 (0.1, 18.1) μg/L, and TRAcP 5b: −2.3 (−3.9, −0.7) U/L. At Tanner stages 3–5 and after the intervention was terminated, bone turnover markers were similar in the intervention and the control children.

Conclusion

Daily school PA in the late prepubertal and early pubertal periods is associated with higher bone formation and lower bone resorption than school PA 1–2 times/week. In late pubertal and postpubertal periods, bone formation and resorption were similar. Termination of the intervention is not associated with adverse bone turnover, indicating that PA-induced bone mass benefits gained during growth may remain in adulthood.

Overuse Elbow Injuries in Youth Gymnasts

BACKGROUND

Gymnastics is a unique sport that places significant loads across the growing elbow, resulting in unique overuse injuries, some of which are poorly described in the current literature.

PURPOSE

To provide a comprehensive review of the unique overuse elbow injuries seen in youth gymnasts and to provide an up-to-date synthesis of the available literature and clinical expertise guiding treatment decisions in this population.

STUDY DESIGN

Narrative review.

METHODS

A review of the PubMed database was performed to include all studies describing elbow biomechanics during gymnastics, clinical entities of the elbow in gymnasts, and outcomes of operative and/or nonoperative treatment of elbow pathology in gymnasts.

RESULTS

Participation in gymnastics among youth athletes is high, being the sixth most common sport in children. Early specialization is the norm in this sport, and gymnastics also has the highest number of participation hours of all youth sports. As a result, unique overuse elbow injuries are common, primarily on the lateral side of the elbow. Beyond common diagnoses of radiocapitellar plica and osteochondritis dissecans of the capitellum, we describe a pathology unique to gymnasts involving stress fracture of the radial head. Additionally, we synthesized our clinical experience and expertise in gymnastics to provide a sport-specific rehabilitation program that can be used by providers treating surgical and nonsurgical conditions of the elbow and wishing to provide detailed activity instructions to their athletes.

CONCLUSION

Overuse injuries of the elbow are common in gymnastics and include osteochondritis dissecans of the capitellum, radiocapitellar plica syndrome, and newly described radial head stress fractures. A thorough understanding of the psychological, cultural, and biomechanical aspects of gymnastics are necessary to care for these athletes.

An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness

Achilles tendon adaptation is a key aspect of exercise performance and injury risk prevention. However, much debate exists about the adaptation of the Achilles tendon in response to exercise activities. Most published research is currently limited to elite athletes and selected exercise activities. Also, existing studies on tendon adaptation do not control for genetic variation. Our explorative cross-sectional study investigated the effects of regular recreational exercise activities on Achilles tendon mechanical properties in 40 identical twin pairs. Using a handheld oscillation device to determine Achilles tendon mechanical properties, we found that the Achilles tendon appears to adapt to regular recreational exercise at comparatively low intensities by increasing its stiffness. Active twins showed a 28% greater Achilles tendon stiffness than their inactive twin (p < 0.05). Further, our research extends existing ideas on sport-specific adaptation by showing that tendon stiffness seemed to respond more to exercise activities that included an aerial phase such as running and jumping. Interestingly, the comparison of twin pairs revealed a high variation of Achilles tendon stiffness (305.4–889.8 N/m), and tendon adaptation was only revealed when we controlled for genetic variance. Those results offer new insights into the impact of genetic variation on individual Achilles tendon stiffness, which should be addressed more closely in future studies.

Force-velocity relationship profile of elbow flexors in male gymnasts

Background

The theoretical maximum force (F₀), velocity (V₀), and power (P_max) of athletes calculated from the relationship between force and velocity (F-V relationship) and the slope of the F-V relationship, reflect their competitive and training activity profiles. Evaluating the F-V relationship of athletes facilitates categorizing the profiles of dynamic muscle functions in relation to long-term sport-specific training. For gymnastics, however, no studies have tried to examine the profiles of F-V relation and power output for upper limb muscles in relation to the muscularity, while the use of the upper extremities in this sport is very unique as described earlier.

Purpose

It was hypothesized that the F-V relationship of the elbow flexion in gymnasts might be characterized by low capacity for generating explosive force, notably in terms of the force normalized to muscle size.

Methods

The F₀, V₀, and P_max derived from the force-velocity relationship during explosive elbow flexion against six different loads (unloaded condition, 15, 30, 45, 60, and 75% of maximal voluntary isometric elbow flexion force (MVF_EF)) for 16 gymnasts (GYM) and 22 judo athletes (JD). F₀ and P_max were expressed as values relative to the cross-sectional area index (CSA_index) of elbow flexors (F₀/CSA_index and P_max/CSA_index, respectively), which was calculated from muscle thickness in the anterior upper arm. The electromyogram (EMG) activities of the biceps brachii (BB) during the maximal isometric and dynamic tasks were also determined.

Results

There were no significant differences in CSA_index of elbow flexors between GYM and JD. MVF_EF/CSA_index for GYM was significantly lower than that for JD. Force was linearly associated with velocity in the dynamic elbow flexion for all the participants (r =  − 0.997 to −0.905 for GYM, r =  − 0.998 to −0.840 for JD). F₀, F₀/ CSA_index, V₀, P_max, P_max/CSA_index, and MVF_EF were significantly lower in GYM than in JD. The activity levels of BB during the dynamic tasks tended to be lower in GYM than in JD at load of <45%MVC.

Conclusion

Gymnasts cannot generate explosive elbow flexion force corresponding to their muscle size. This may be due to low neuromuscular activities during the maximal dynamic tasks against relatively low loads.

May Young Elite Cyclists Have Less Efficient Bone Metabolism?

The purpose of this work was to describe changes in metabolic activity in the bones of young male competitive cyclists (CYC) as compared with age-matched controls (CON) over a one-year period of study. Eight adolescent male cyclists aged between fourteen and twenty, and eight age-matched controls participated in this longitudinal study. Serum osteocalcin (OC), amino-terminal propeptide of type I procollagen (PINP), beta-isomerized C-telopeptides (β-CTx) and plasma 25 hydroxyvitamin D [25(OH)D], were investigated by an electrogenerated chemiluminescence immunoassay. Analysis of variance revealed no significant differences in formation and resorption markers between cyclists and controls. Within the groups, both CYC and CON showed decreased OC at -30% and -24%, respectively, and PINP where the figures were -28% and -30% respectively (all p < 0.05). However, only the CYC group showed a decrease in [25(OH)D], lower by 11% (p < 0.05). The similarity in the concentrations of markers in cyclists and controls seems to indicate that cycling does not modify the process of bone remodeling. The decrease in vitamin D in cyclists might be detrimental to their future bone health.

Kinetic analysis of push-up exercises: a systematic review with practical recommendations

Push-ups represent one of the simplest and most popular strengthening exercise. The aim of this study was to systematically review and critically appraise the literature on the kinetics-related characteristics of different types of push-ups, with the objective of optimising training prescription and exercise-related load. A systematic search was conducted in the electronic databases PubMed, Google Scholar and Science Direct up to April 2018. Studies that reported kinetic data (e.g. initial and peak-force supported by the upper-limbs, impact-force, peak-flexion-moment of the elbow-joint, rate of propulsive- and impact-, and vertebral-joint compressive-forces) related to push-ups and included trained, recreational and untrained participants, were considered. The risk of bias in the included studies was assessed using the Critical Appraisal Skills Programme scale. From 5290 articles retrieved in the initial search, only 26 studies were included in this review. Kinetic data for 46 push-up variants were assessed. A limitation of the current review is that the relationship between our findings and actual clinical or practical consequences is not statistically proven but can only be inferred from our critical descriptive approach. Overall, this review provides detailed data on specific characteristics and intensities of push-up variations, in order to optimise exercise prescription for training and rehabilitation purposes.

Upper and lower limb loading during weight-bearing activity in children: reaction forces and influence of body weight

Weight bearing (WB) activity is important for healthy skeletal development. The magnitude of loading during WB activities, especially upper limb impacts, has yet to be quantified in children. This study quantifies ground reaction forces (GRF) experienced by children performing WB activities and examines the contribution of body weight (BW) to GRF. Fifty children, aged 8-12 were recruited (34 males). GRF were measured using force plates during 20 upper and lower limb activities (such as landing on the feet and hands). Sex differences in GRF and associations between peak force and BW were examined using independent sample t-tests and linear regressions (p < 0.05), respectively. Lower limb GRF varied from 2-6x BW with no significant sex differences. GRF during upper limb activities varied from 1/3-1.7x BW with males experiencing significantly greater GRF for 25% of activities. BW was significantly associated with peak force in almost all activities; however, GRF variation explained by BW was wide-ranging across activities and not dependent on limb or activity type (static vs dynamic). Therefore, factors other than BW, such as technique, may be important in determining forces experienced by children performing WB activity and should be considered when choosing activities for WB activity interventions.

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.

Structural Strength Benefits Observed at the Hip of Premenarcheal Gymnasts Are Maintained Into Young Adulthood 10 Years After Retirement From the Sport

PURPOSE

Premenarcheal female gymnasts have been consistently found to have greater bone mass and structural advantages. However, little is known about whether these structural advantages are maintained after the loading stimulus is removed. Therefore, the purpose of this study was to investigate the structural properties at the hip after long-term retirement from gymnastics.

METHODS

Structural properties were derived from dual-energy X-ray absorptiometry scans using the hip structural analysis program for the same 24 gymnasts and 21 nongymnasts both in adolescence (8-15 y) and adulthood (22-30 y). Structural measures were obtained at the narrow neck, intertrochanter, and femoral shaft and included cross-sectional area, section modulus, and buckling ratio. Multivariate analysis of covariance was used to assess differences between groups in bone measures while controlling for size, age, maturity, and physical activity.

RESULTS

Gymnasts were found to have structural advantages at the narrow neck in adolescence (16% greater cross-sectional area, 17% greater section modulus, and 25% lower buckling ratio) and 14 years later (13% greater cross-sectional area and 26% lower buckling ratio). Benefits were also found at the intertrochanter and femoral shaft sites in adolescence and adulthood.

CONCLUSION

Ten years after retirement from gymnastics, former gymnasts' maintained significantly better hip bone structure than females who did not participate in gymnastics during growth.

Bone Health of Young Male Gymnasts: A Systematic Review

PURPOSE

To synthesize existing literatures on the impact of gymnastics participation on the skeletal health of young male gymnasts.

METHODS

Following a systematic search, 12 studies were included in this review. Quality of included studies was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE modified) criteria.

RESULTS

Assessment of skeletal health varied between and within imaging modality protocols. Gymnasts had higher total bone content, greater total and trabecular bone density, larger bone size, a thicker cortex, and higher estimates of bone strength than controls. Recreational studies reported no difference in height or weight between gymnasts and controls; however, elite gymnasts were shorter and lighter than nongymnasts. STROBE scores ranged from 65% to 95%.

CONCLUSION

Gymnastics participation may be beneficial to the bone health of young males as gymnasts had higher bone density and bone mineral content, larger bones, and greater estimates of bone strength than controls.

Technique Selection 'the Coaches Challenge' Influencing Injury Risk During the First Contact Hand of the Round off Skill in Female Gymnastics

The importance of technique selection on elbow injury risk has been identified for the key round off skill in female gymnastics, with a focus on the second contact limb. The aim of this study was to shift the focus to the first contact limb and investigate the biomechanical injury risk during parallel and T-shape round-off (RO) techniques. Seven international-level female gymnasts performed 10 trials of the RO to back-handspring with parallel and T-shape hand positions. Synchronized kinematic (3D motion analysis system; 247 Hz) and kinetic (two force plates; 1235 Hz) data were collected for each trial. The t-test with effect size statistics determined differences between the two techniques. No significant differences were found for vertical, anterior posterior and resultant ground reaction force, elbow joint kinematics and kinetics. Specifically, the results highlighted that change in technique in RO skills did not influence first contact limb elbow joint mechanics and therefore, injury risk. The findings of the present study suggest the injury potential of this skill is focused on the second limb during the parallel technique of this fundamental gymnastic skill.

Osteopathology in the Equine Distal Phalanx Associated With the Development and Progression of Laminitis

Although the equine distal phalanx and hoof lamellae are biomechanically and physiologically integrated, bony changes in the distal phalanx are poorly described in laminitis. The aims of this study were (1) to establish a laminitis grading scheme that can be applied to the wide spectrum of lesions seen in naturally occurring cases and (2) to measure and describe changes in the distal phalanx associated with laminitis using micro-computed tomography (micro-CT) and histology. Thirty-six laminitic and normal feet from 15 performance and nonperformance horses were evaluated. A laminitis grading scheme based on radiographic, gross, histopathologic, and temporal parameters was developed. Laminitis severity grades generated by this scheme correlated well with clinical severity and coincided with decreased distal phalanx bone volume and density as measured by micro-CT. Laminitic hoof wall changes included progressive ventral rotation and distal displacement of the distal phalanx with increased thickness of the stratum internum-corium tissues with lamellar wedge formation. Histologically, there was epidermal lamellar necrosis with basement membrane separation and dysplastic regeneration, including acanthosis and hyperkeratosis, corresponding to the lamellar wedge. The changes detected by micro-CT corresponded to microscopic findings in the bone, including osteoclastic osteolysis of trabecular and osteonal bone with medullary inflammation and fibrosis. Bone changes were identified in horses with mild/early stages of laminitis as well as severe/chronic stages. The authors conclude that distal phalangeal pathology is a quantifiable and significant component of laminitis pathology and may have important implications for early detection or therapeutic intervention of equine laminitis.

A longitudinal study of bone area, content, density, and strength development at the radius and tibia in children 4-12 years of age exposed to recreational gymnastics

This study investigated the long-term relationship between the exposure to childhood recreational gymnastics and bone measures and bone strength parameters at the radius and tibia. It was observed that individuals exposed to recreational gymnastics had significantly greater total bone content and area at the distal radius. No differences were observed at the tibia.

INTRODUCTION

This study investigated the relationship between exposure to early childhood recreational gymnastics with bone measures and bone strength development at the radius and tibia.

METHODS

One hundred twenty seven children (59 male, 68 female) involved in either recreational gymnastics (gymnasts) or other recreational sports (non-gymnasts) between 4 and 6 years of age were recruited. Peripheral quantitative computed tomography (pQCT) scans of their distal and shaft sites of the forearm and leg were obtained over 3 years, covering the ages of 4-12 years at study completion. Multilevel random effects models were constructed to assess differences in the development of bone measures and bone strength measures between those exposed and not exposed to gymnastics while controlling for age, limb length, weight, physical activity, muscle area, sex, and hours of training.

RESULTS

Once age, limb length, weight, muscle area, physical activity, sex, and hours of training effects were controlled, it was observed that individuals exposed to recreational gymnastics had significantly greater total bone area (18.0 ± 7.5 mm(2)) and total bone content (6.0 ± 3.0 mg/mm) at the distal radius (p < 0.05). This represents an 8-21 % benefit in ToA and 8-15 % benefit to ToC from 4 to 12 years of age. Exposure to recreational gymnastics had no significant effect on bone measures at the radius shaft or at the tibia (p > 0.05).

CONCLUSIONS

Exposure to early life recreational gymnastics provides skeletal benefits to distal radius bone content and area. Thus, childhood recreational gymnastics exposure may be advantageous to bone development at the wrist.

Impact of Walking and Running on the Heel bone: the Adventist Health Study-2

Aims

Physical activity is well recognized for its bone health benefit. We examined the benefit of walk/run/jog on bone health using broadband ultrasound attenuation (BUA) of the calcaneus.

Methodology

Caucasian and African American males (n=593) and females (n=1,106) had their calcaneal BUA measured two years later after enrollment into the AHS-2. The association between calcaneal BUA (dB/Mhz) and the distance of walk/run/ jog level per week (miles) was assessed using multiple linear regression.

Results

In a multivariable model adjusted for important covariates, BUA was positively associated with BMI (P < .001), total calcium intake (P =0.31), total protein intake (P =0.38) and inversely associated with age (P < .001) and smoking (P < .05). Compared to women who did not walk/ run/ jog, women walking 10 or more miles per week had an increase in BUA by 4.08 (dB/Mhz) (P _trend=0.03). Similarly, compared to men who did not walk/ run/ jog, men walking 10 or more miles per week had an increase in BUA by 5.97 (dB/Mhz) (P _trend=0.01).

Conclusions

We concluded that BUA is positively associated with walk/ run/jog after accounting for age, BMI, smoking status, calcium intake, protein intake and estrogen usage.

An in-school exercise intervention to enhance bone and reduce fat in girls: the CAPO Kids trial

The CAPO Kids trial was a 9-mo, controlled, school-based intervention to examine the effects of a novel, brief, high intensity exercise regime on indices of musculoskeletal and metabolic health in pre- and early-pubertal girls.

METHODS

A total of 151 pre- and early-pubertal girls (10.6±0.6years), recruited from two different schools consented to participate; 76 in the exercise group (EX) and 75 in the control group (CON). EX performed 10min bouts of thrice-weekly jumping plus capoeira (a Brazilian sport that combines martial art with dance), along with usual physical education (PE) activities. CON continued usual PE alone. Maturity, weight, height, waist circumference, resting heart rate and blood pressure, maximal vertical jump, and aerobic capacity were determined using standard clinical and field measures. Calcaneal broadband ultrasound attenuation (BUA) and stiffness index (SI) were determined from quantitative ultrasonometry. A subsample of children also underwent DXA and pQCT measures. Prior physical activity participation and daily calcium consumption were determined from validated instruments.

RESULTS

EX girls improved BUA more than CON (+4.5% vs. +1.4%, p=0.019). Resting heart rate (-7.2% vs. -1.8%, p<0.01), maximal vertical jump (+13.4% vs. -1.2%, p<0.001), estimated maximal oxygen consumption (+10.6% vs. +1.0%, p<0.001), and waist circumference (+2.7% vs. +5.6%, p<0.001) also improved more for EX than CON.

CONCLUSION

Ten minutes of high intensity exercise (capoeira and jumping) three times a week in the primary school setting enhances musculoskeletal and metabolic outcomes in pre- and early-pubertal girls without disrupting the academic schedule. The programme, amenable to broad-scale school implementation, would confer meaningful public health benefits.

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.

Role of intensive training in the growth and maturation of artistic gymnasts

Short stature and later maturation of youth artistic gymnasts are often attributed to the effects of intensive training from a young age. Given limitations of available data, inadequate specification of training, failure to consider other factors affecting growth and maturation, and failure to address epidemiological criteria for causality, it has not been possible thus far to establish cause–effect relationships between training and the growth and maturation of young artistic gymnasts. In response to this ongoing debate, the Scientific Commission of the International Gymnastics Federation (FIG) convened a committee to review the current literature and address four questions: (1) Is there a negative effect of training on attained adult stature? (2) Is there a negative effect of training on growth of body segments? (3) Does training attenuate pubertal growth and maturation, specifically, the rate of growth and/or the timing and tempo of maturation? (4) Does training negatively influence the endocrine system, specifically hormones related to growth and pubertal maturation? The basic information for the review was derived from the active involvement of committee members in research on normal variation and clinical aspects of growth and maturation, and on the growth and maturation of artistic gymnasts and other youth athletes. The committee was thus thoroughly familiar with the literature on growth and maturation in general and of gymnasts and young athletes. Relevant data were more available for females than males. Youth who persisted in the sport were a highly select sample, who tended to be shorter for chronological age but who had appropriate weight-for-height. Data for secondary sex characteristics, skeletal age and age at peak height velocity indicated later maturation, but the maturity status of gymnasts overlapped the normal range of variability observed in the general population. Gymnasts as a group demonstrated a pattern of growth and maturation similar to that observed among short-, normal-, late-maturing individuals who were not athletes. Evidence for endocrine changes in gymnasts was inadequate for inferences relative to potential training effects. Allowing for noted limitations, the following conclusions were deemed acceptable: (1) Adult height or near adult height of female and male artistic gymnasts is not compromised by intensive gymnastics training. (2) Gymnastics training does not appear to attenuate growth of upper (sitting height) or lower (legs) body segment lengths. (3) Gymnastics training does not appear to attenuate pubertal growth and maturation, neither rate of growth nor the timing and tempo of the growth spurt. (4) Available data are inadequate to address the issue of intensive gymnastics training and alterations within the endocrine system.

Muscle function, dynamic loading, and femoral neck structure in pediatric females

PURPOSE

Muscle forces influence the development of bone mass and structure, but dynamic loading via impact exercise is considered particularly osteogenic. We hypothesized that indices of local muscle function and physical activity exposure would predict femoral neck (FN) structure in premenarcheal females.

METHODS

We tested this hypothesis in 76 healthy, premenarcheal girls (46 gymnasts and 30 nongymnasts). Height, weight, Tanner breast stage, and prior year nonaquatic, organized physical activity level (PAL) were recorded semiannually. Hologic dual-energy x-ray absorptiometry scans (whole body, left FN) yielded total body nonbone lean mass and bone outcomes, including narrow neck (NN) hip structural analysis data. Dynamometers assessed nondominant hand grip and left hip flexion/extension indices. Parsimonious regression models tested the following as predictors of bone outcomes: local muscle function, PAL, gymnast status, and lean mass, accounting for Tanner breast stage and height, as appropriate.

RESULTS

Hip flexion indices were significantly correlated with indices of FN mass, density, structure, and strength (P < 0.05). However, the entry of PAL, gymnast status, and lean mass into regression models supplanted local muscle function explanatory value. In contrast, for many variables, the significant association of gymnast status persisted after accounting for physical maturity, body size/lean mass, and PAL. For all skeletal indices except FNArea, NNwidth, NN endosteal diameter, and NN buckling ratio, gymnast status was more strongly associated with bone outcomes than PAL.

CONCLUSIONS

Greater activity doses and exposure to extreme dynamic loading provide independent benefits to FN structure during growth. Furthermore, weight-bearing activity and high-impact exercise exposure appear superior to local muscle force measures for prediction of FN structure.

Enhanced bone mass and physical fitness in prepubescent basketball players

The aim of this study was to examine the effect of basketball practice on bone acquisition in the prepubertal age. In total, 48 prepubescent male basketball players aged 11.1 ± 0.8 yr, Tanner stage 1, were compared with 50 controls matched for age and pubertal stage. Areal bone mineral density, bone mineral content (BMC), and bone area (BA) in deferent sites associated with anthropometric parameters were measured by dual-energy X-ray absorptiometry. Running and jumping tests were performed. Analysis of Student's impaired t-test revealed that basketball players attained better results in all physical fitness tests (p < 0.05). They also exhibited significantly greater BMC and BA in whole body, upper and lower extremities, trochanter, total hip, and whole right and left radius (p < 0.001) compared with the controls. No significant differences were observed between groups in right and left ultradistal and third distal radius and spinal regions, BMC, and BA, whereas a significant positive correlation was reported between lean mass, BMC, and BA of lower limbs. In summary, basketball practice in prepubertal age is associated with improved physical fitness and enhanced lean and bone mass in loaded sites.

Structural strength development at the proximal femur in 4- to 10-year-old precompetitive gymnasts: a 4-year longitudinal hip structural analysis study

Gymnastics, a high-impact weight-bearing physical activity, has been shown to be highly osteogenic. Previously in this cohort, bone mass development (bone mineral content accrual [BMC]) was shown to be positively associated with low-level (recreational) gymnastics exposure (1 to 2 hours per week); however, BMC is only one single component of bone strength. Bone strength is influenced not only by bone mineralization but also bone geometry, bone architecture, and the imposing loads on the bone. The aim of this study was to investigate whether low-level gymnastics training influenced the estimated structural geometry development at the proximal femur. A total of 165 children (92 gymnasts and 73 non-gymnasts) between the ages of 4 and 6 years were recruited into this study and assessed annually for 4 years. During the 4 years, 64 gymnasts withdrew from the sport and were reclassified as ex-gymnasts. A dual-energy X-ray absorptiometry (DXA) image of each child's hip was obtained. Values of cross-sectional area (CSA), section modulus (Z), and cortical thickness (CT) at the narrow neck (NN), intertrochanter (IT), and shaft (S) were estimated using the hip structural analysis (HSA) program. Multilevel random-effects models were constructed and used to develop bone structural strength development trajectories (estimate ± SEE). Once the confounders of body size and lifestyle were controlled, it was found that gymnasts had 6% greater NN CSA than non-gymnasts controls (0.09 ± 0.03 cm(2) , p < 0.05), 7% greater NN Z (0.04 ± 0.01 cm(3) , p < 0.05), 5% greater IT CSA (0.11 ± 0.04 cm(3) , p < 0.05), 6% greater IT Z (0.07 ± 0.03 cm(3) , p < 0.05), and 3% greater S CSA (0.06 ± 0.03 cm(3) , p < 0.05). These results suggest that early exposure to low-level gymnastics participation confers benefits related to geometric and bone architecture properties during childhood and, if maintained, may improve bone health in adolescence and adulthood.

Specific sites of bone expansion depend on the level of volleyball practice in prepubescent boys

The purpose of this study was to investigate the effect of 18 months of high and low levels of volleyball practice on bone acquisition. 130 prepubescent boys (mean age 11.4 ± 0.7) were divided into a high-level training group (HLG), low-level training group (LLG), and controls. Bone mineral content (BMC) and bone area at the whole body, lumbar spine L2-L4, femoral neck of the dominant leg, and right and left radius were measured using dual-photon X-ray absorptiometry. Enhanced BMC resulted from high-training volleyball activity in all measured sites except the third left and right distal radius, which is not modified by low-level training in prepubescent players but it was accompanied by a bone area expansion in radius and weight-bearing sites for the HLG, and in legs, whole right and left radius for the LLG. Significant improvement of skeletal tissues is associated with the intensity and duration of volleyball training.

Peripubertal female athletes in high-impact sports show improved bone mass acquisition and bone geometry

OBJECTIVE

Intensive physical training may have a sport-dependent effect on bone mass acquisition. This cross-sectional study evaluated bone mass acquisition in girls practicing sports that put different mechanical loads on bone.

MATERIALS/METHODS

Eighty girls from 10.7 to 18.0 years old (mean 13.83 ± 1.97) were recruited: 20 artistic gymnasts (AG; high-impact activity), 20 rhythmic gymnasts (RG; medium-impact activity), 20 swimmers (SW, no-impact activity), and 20 age-matched controls (CON; leisure physical activity <3h/wk). Areal bone mineral density (aBMD) was determined using DEXA. Hip structural analysis applied at the femur evaluated cross-sectional area (CSA, cm(2)), section modulus (Z, cm(3)), and buckling ratio. Bone turnover markers and OPG/RANKL levels were analyzed.

RESULTS

AG had higher aBMD than SW and CON at all bone sites and higher values than RG in the lumbar spine and radius. RG had higher aBMD than SW and CON only in the femoral region. CSA and mean cortical thickness were significantly higher and the buckling ratio was significantly lower in both gymnast groups compared with SW and CON. In RG only, endocortical diameter and width were reduced, while Z was only increased in AG compared with SW and CON. Reduced bone remodeling was observed in RG compared with AG only when groups were subdivided according to menarcheal status. All groups showed similar OPG concentrations, while RANKL concentrations increased with age and were decreased in SW.

CONCLUSION

High-impact activity clearly had a favorable effect on aBMD and bone geometry during the growth period, although the bone health benefits seem to be more marked after menarche.

Quantitative Ultrasound and bone's response to exercise: a meta analysis

The utility of Quantitative Ultrasound (QUS) for assessing and monitoring changes in bone health due to exercise is limited for lack of adequate research evidence. Restrictions to bone density testing and the enduring debate over repeat dual energy absorptiometry testing spells uncertainty over clinical and non-clinical evaluation of exercise for prevention of osteoporosis. This study, via systematic review and meta-analysis, aimed to paint a portrait of current evidence regarding QUS' application to monitoring bone's adaptive response to exercise interventions.

METHODS

Structured and comprehensive search of databases was undertaken along with hand-searching of key journals and reference lists to locate relevant studies published up to December 2011. Twelve articles met predetermined inclusion criteria. The effect of exercise interventions for improving bone health, as measured by QUS of the calcaneum, was examined across the age spectrum. Study outcomes for analysis: absolute (dB/MHz) or relative change (%) in broadband ultrasound attenuation (BUA) and/or os calcis stiffness index were compared by calculating standardised mean difference (SMD) using fixed- and random-effects models.

RESULTS

Quality of included trials varied from low to high on a scale of one to three. Four to 36months of exercise led to a significant improvement in calcaneum BUA (0.98 SMD, 95% CI 0.80, 1.16, overall effect Z-value=10.72, p=0.001) across the age spectrum.

CONCLUSION

The meta-analysis attests to the sensitivity of QUS to exercise-induced changes in bone health across the age groups. QUS may be considered for use in exercise-based bone health interventions for preventing osteoporosis.

Former premenarcheal gymnasts exhibit site-specific skeletal benefits in adulthood after long-term retirement

Young female gymnasts have greater bone strength compared to controls; although possibly due to selection into gymnastics, it is thought that their loading activity during growth increases their bone mass, influencing both bone geometry and architecture. If such bone mass and geometric adaptations are maintained, this may potentially decrease the risk of osteoporosis and risk of fracture later in life. However, there is limited evidence of the persisting benefit of gymnastic exercise during growth on adult bone geometric parameters. Therefore, the purpose of this study was to determine whether adult bone geometry, volumetric density, and estimated strength were greater in retired gymnasts compared to controls, 10 years after retirement from the sport. Bone geometric and densitometric parameters, measured by peripheral quantitative computed tomography (pQCT) at the radius and tibia, were compared between 25 retired female gymnasts and 22 controls, age range 22 to 30 years, by multivariate analysis of covariance (covariates: age, height, and muscle cross-sectional area). Retired gymnasts had significantly greater adjusted total and trabecular area (16%), total and trabecular bone mineral content (BMC) (18% and 22%, respectively), and estimated strength (21%) at the distal radius (p < 0.05) than controls. Adjusted total and cortical area and BMC, medullary area, and estimated strength were also significantly greater (13% to 46%) in retired gymnasts at the 30% and 65% radial shaft sites (p < 0.05). At the distal tibia, retired gymnasts had 12% to 13% greater total and trabecular BMC and volumetric bone mineral density as well as 21% greater estimated strength; total and cortical BMC and estimated strength were also greater at the tibial shaft (8%, 11%, and 10%, respectively) (p < 0.05). Former female gymnasts have significantly better geometric and densitometric properties, as well as estimated strength, at the radius and tibia 10 years after retirement from gymnastics compared to females who did not participate in gymnastics in childhood and adolescence.

Site-specific advantages in skeletal geometry and strength at the proximal femur and forearm in young female gymnasts

PURPOSE

We evaluated site-specific skeletal adaptation to loading during growth, comparing radius (RAD) and femoral neck (FN) DXA scans in young female gymnasts (GYM) and non-gymnasts (NON).

METHODS

Subjects from an ongoing longitudinal study (8-26yr old) underwent annual DXA scans (proximal femur, forearm, total body) and anthropometry, completing maturity and physical activity questionnaires. This cross-sectional analysis used the most recent data meeting the following criteria: gynecological age ≤2.5yr post-menarche; and GYM annual mean gymnastic exposure ≥5.0h/wk in the prior year. Bone geometric and strength indices were derived from scans for 173 subjects (8-17yr old) via hip structural analysis (femoral narrow neck, NN) and similar radius formulae (1/3 and Ultradistal (UD)). Maturity was coded as M1 (Tanner I breast), M2 (pre-menarche, ≥Tanner II breast) or M3 (post-menarche). ANOVA and chi square compared descriptive data. Two factor ANCOVA adjusted for age, height, total body non-bone lean mass and percent body fat; significance was tested for main effects and interactions between gymnastic exposure and maturity.

RESULTS

At the distal radius, GYM means were significantly greater than NON means for all variables (p<0.05). At the proximal femur, GYM exhibited narrower periosteal and endosteal dimensions, but greater indices of cortical thickness, BMC, aBMD and section modulus, with lower buckling ratio (p<0.05). However, significant interactions between maturity and loading were detected for the following: 1) FN bone mineral content (BMC) and NN buckling ratio (GYM BMC advantages only in M1 and M3; for BMC and buckling ratio, M1 advantages were greatest); 2) 1/3 radius BMC, width, endosteal diameter, cortical cross-sectional area, and section modulus (GYM advantages primarily post-menarche); and 3) UD radius BMC and axial compressive strength (GYM advantages were larger with greater maturity, greatest post-menarche).

CONCLUSIONS

Maturity-specific comparisons suggested site-specific skeletal adaptation to loading during growth, with greater advantages at the radius versus the proximal femur. At the radius, GYM advantages included greater bone width, cortical cross-sectional area and cortical thickness; in contrast, at the femoral neck, GYM bone tissue cross-sectional area and cortical thickness were greater, but bone width was narrower than in NON. Future longitudinal analyses will evaluate putative maturity-specific differences.

The Lichfield bone study: the skeletal response to exercise in healthy young men

The skeletal response to short-term exercise training remains poorly described. We thus studied the lower limb skeletal response of 723 Caucasian male army recruits to a 12-wk training regime. Femoral bone volume was assessed using magnetic resonance imaging, bone ultrastructure by quantitative ultrasound (QUS), and bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA) of the hip. Left hip BMD increased with training (mean ± SD: 0.85 ± 3.24, 2.93 ± 4.85, and 1.89 ± 2.85% for femoral neck, Ward's area, and total hip, respectively; all P < 0.001). Left calcaneal broadband ultrasound attenuation rose 3.57 ± 0.5% (P < 0.001), and left and right femoral cortical volume by 1.09 ± 4.05 and 0.71 ± 4.05%, respectively (P = 0.0001 and 0.003), largely through the rise in periosteal volume (0.78 ± 3.14 and 0.59 ± 2.58% for right and left, respectively, P < 0.001) with endosteal volumes unchanged. Before training, DXA and QUS measures were independent of limb dominance. However, the dominant femur had higher periosteal (25,991.49 vs. 2,5572 mm(3), P < 0.001), endosteal (6,063.33 vs. 5,983.12 mm(3), P = 0.001), and cortical volumes (19,928 vs. 19,589.56 mm(3), P = 0.001). Changes in DXA, QUS, and magnetic resonance imaging measures were independent of limb dominance. We show, for the first time, that short-term exercise training in young men is associated not only with a rise in human femoral BMD, but also in femoral bone volume, the latter largely through a periosteal response.

Longitudinal changes in bone mineral density in male master cyclists and nonathletes

This study tracked changes in bone mineral density (BMD) over a 7-year period in competitive male master cyclists (n = 19) and nonathletes (n = 18). Participants completed health/exercise history and food frequency (for calcium intake) questionnaires and underwent BMD testing by dual-energy X-ray absorptiometry. At initial and 7-year assessments, there was a consistent pattern of lower BMD in cyclists compared to nonathletes at all bone sites measured. Repeated measures analysis of covariance adjusted for changes in body mass index, lean mass, calcium intake, and exercise habits indicated a significant interaction at the total body site, indicating greater BMD decline in cyclists than nonathletes (p < 0.05). Among all study participants, those who reported participating in weight training or impact exercise since the baseline assessment lost significantly less BMD at the spine and femoral neck compared to participants who reported no weight training/impact exercise since baseline (p < 0.05). A significantly greater percentage of cyclists than nonathletes met the International Society of Clinical Densitometry criteria for osteopenia or osteoporosis at baseline (84.2% vs. 50.0%) and at follow-up (89.5% vs. 61.1%, p < 0.05). Further, 6 of the 19 (31.6%) cyclists who had osteopenia at baseline became osteoporotic, compared to 1 (5.6%) of the nonathletes. The high percentage of male master cyclists with low BMD, combined with a high risk for fracture from falls associated with competitive cycling, warrant attention among this population. Coaches and health professionals interacting with cyclists need to promote alternative exercise such as weight training, plyometrics, or other high impact activity as a complement to cycle training to help minimize bone loss in this population.

Bone mineral accrual in 4- to 10-year-old precompetitive, recreational gymnasts: a 4-year longitudinal study

Competitive female gymnasts have greater bone mineral measures than nongymnasts. However, less is known about the effect of recreational and/or precompetitive gymnastics participation on bone development. The purpose of this study was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics. One hundred and sixty-three children (30 gymnasts, 61 ex-gymnasts, and 72 nongymnasts) between 4 and 6 years of age were recruited and measured annually for 4 years (not all participants were measured at every occasion). Total-body (TB), lumbar spine (LS), and femoral neck (FN) bone mineral content (BMC) were measured by dual-energy X-ray absorptiometry (DXA). Multilevel random-effects models were constructed and used to predict differences in TB, LS, and FN BMC between groups while controlling for differences in body size, physical activity, and diet. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at year 4 (p < .05). No differences were found at the LS between groups, and there were no differences between ex-gymnasts' and nongymnasts' bone parameters (p > .05). These findings suggest that recreational and precompetitive gymnastics participation is associated with greater BMC. This is important because beginner gymnastics skills are attainable by most children and do not require a high level of training. Low-level gymnastics skills can be implemented easily into school physical education programs, potentially affecting skeletal health.

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.

Body Composition of Young Athletes

Absolute and relative components of body mass are a primary focus in studies of body composition. Components change with growth and maturation, requiring care in selecting methods of assessment in children and adolescents. Although sex differences are apparent in fat-free mass (FFM), fat mass (FM), and relative fatness (% Fat) during childhood, they are more clearly defined during adolescence and adulthood. Body composition is one of many determinants of sport performance, but % Fat tends to be the primary focus of discussion in young athletes. The influence of training for sport on bone mineral has received more attention in recent years because of methodological advances in assessment and concern for potential negative effects of altered menstrual function on bone. Relative fatness of young athletes in several sports is summarized, and issues related to sport training and body composition in young athletes are considered. Suggestions for dealing with body composition in young athletes are provided.

Precompetitive and recreational gymnasts have greater bone density, mass, and estimated strength at the distal radius in young childhood

Young recreational and precompetitive gymnasts had, on average, 23% greater bone strength at the wrist compared to children participating in other recreational sports. Recreational gymnastics involves learning basic movement patterns and general skill development and as such can easily be implemented into school physical education programs potentially impacting skeletal health.

INTRODUCTION

Competitive gymnasts have greater bone mass, density, and estimated strength. The purpose of this study was to investigate whether the differences reported in the skeleton of competitive gymnasts are also apparent in young recreational and precompetitive gymnasts.

METHODS

One hundred twenty children (29 gymnasts, 46 ex-gymnasts, and 45 non-gymnasts) between 4 and 9 years of age (mean = 6.8 ± 1.3) were measured. Bone mass, density, structure, and estimated strength were determined using peripheral quantitative computed tomography at the distal (4%) and shaft (65%, 66%) sites in the radius and tibia. Total body, hip, and spine bone mineral content (BMC) was assessed using dual energy X-ray absorptiometry. Analysis of covariance (covariates of sex, age and height) was used to investigate differences in total bone content (ToC), total bone density (ToD), total bone area (ToA), and estimated strength (BSI) at the distal sites and ToA, cortical content (CoC), cortical density (CoD), cortical area (CoA), cortical thickness, medullary area, and estimated strength (SSIp) at the shaft sites.

RESULTS

Gymnasts and ex-gymnasts had 5% greater adjusted total body BMC and 6-25% greater adjusted ToC, ToD, and BSI at the distal radius compared to non-gymnasts (p < 0.05). Ex-gymnasts had 7-11% greater CoC and CoA at the radial shaft and 5-8% greater CoC and SSIp at the tibial shaft than gymnasts and non-gymnasts. Ex-gymnasts also had 12-22% greater ToC and BSI at the distal tibia compared to non-gymnasts (p < 0.05).

CONCLUSION

This data suggests that recreational and precompetitive gymnastics participation is associated with greater bone strength.

Distal radius geometry and skeletal strength indices after peripubertal artistic gymnastics

Development of optimal skeletal strength should decrease adult bone fragility. Nongymnasts (NON): were compared with girls exposed to gymnastics during growth (EX/GYM: ), using peripheral quantitative computed tomography (pQCT) to evaluate postmenarcheal bone geometry, density, and strength. Pre- and perimenarcheal gymnastic loading yields advantages in indices of postmenarcheal bone geometry and skeletal strength.

INTRODUCTION

Two prior studies using pQCT have reported bone density and size advantages in Tanner I/II gymnasts, but none describe gymnasts' bone properties later in adolescence. The current study used pQCT to evaluate whether girls exposed to gymnastics during late childhood growth and perimenarcheal growth exhibited greater indices of distal radius geometry, density, and skeletal strength.

METHODS

Postmenarcheal subjects underwent 4% and 33% distal radius pQCT scans, yielding: 1) vBMD and cross-sectional areas (CSA) (total bone, compartments); 2) polar strength-strain index; 3) index of structural strength in axial compression. Output was compared for EX/GYM: vs. NON: , adjusting for gynecological age and stature (maturity and body size), reporting means, standard errors, and significance.

RESULTS

Sixteen postmenarcheal EX/GYM: (age 16.7 years; gynecological age 3.4 years) and 13 NON: (age 16.2 years; gynecological age 3.6 years) were evaluated. At both diaphysis and metaphysis, EX/GYM: exhibited greater CSA and bone strength indices than NON; EX/GYM: exhibited 79% larger intramedullary CSA than NON: (p < 0.05). EX/GYM: had significantly higher 4% trabecular vBMD; differences were not detected for 4% total vBMD and 33% cortical vBMD.

CONCLUSIONS

Following pre-/perimenarcheal gymnastic exposure, relative to nongymnasts, postmenarcheal EX/GYM: demonstrated greater indices of distal radius geometry and skeletal strength (metaphysis and diaphysis) with greater metaphyseal trabecular vBMD; larger intramedullary cavity size was particularly striking.

Effects of lifetime loading history on cortical bone density and its distribution in middle-aged and older men

We have reported previously that long-term participation of weight-bearing exercise is associated with increased QCT-derived cortical bone size and strength in middle-aged and older men, but not whole bone cortical volumetric BMD. However, since bone remodeling and the distribution of loading-induced strains within cortical bone are non-uniform, the aim of this study was to examine the effects of lifetime loading history on cortical bone mass distribution and bone shape in healthy community dwelling middle-aged and older men. We used QCT to assess mid-femur and mid-tibia angular bone mass distribution around its center (polar distribution), the bone density distribution through the cortex (radial distribution), and the ratio between the maximum and minimum moments of inertia (I(max)/I(min) ratio) in 281 men aged 50 to 79 years. Current (>50 years) and past (13-50 years) sport and leisure time activity was assessed by questionnaire to calculate an osteogenic index (OI) during adolescence and adulthood. All men were then categorized into a high (H) or low/non impact (L) group according to their OI scores in each period. Three contrasting groups were then formed to reflect weight-bearing impact categories during adolescence and then adulthood: H-H, H-L and L-L. For polar bone mass distribution, bone deposition in the anterolateral, medial and posterior cortices were 6-10% greater at the mid-femur and 9-24% greater at mid-tibia in men in the highest compared to lowest tertile of lifetime loading (p<0.01-<0.001). When comparing the influence of contrasting loading history during adolescence and adulthood, there was a graded response between the groups in the distribution of bone mass at the anterior-lateral and posterior regions of the mid-tibia (H-H>H-L>L-L). For radial bone density distribution, there were no statistically significant effects of loading at the mid-femur, but a greater lifetime OI was associated with a non-significant 10-15% greater bone density near the endocortical region of the mid-tibia. In conclusion, a greater lifetime loading history was associated with region-specific adaptations in cortical bone density.

Use of quantitative ultrasonography for noninvasive surveillance of the third metacarpal bone in racing and training Thoroughbreds

OBJECTIVE-To use quantitative ultrasonography to evaluate the association between the speed of sound (SOS) at 9 sites in the third metacarpal bone (MCIII) of racing Thoroughbreds with workload accumulation and the effect that MCIII failure has on this association. ANIMALS-Sixty-two 2- and 3-year-old Thoroughbreds in racing condition. PROCEDURES-Cumulative work index (CWI) was used to calculate total workload (CWI(total)) and also 3 independent CWIs for the various gaits (ie, trot [CWI(trot)], gallop [CWI(gallop)], and race [CWI(race)]) used during training and racing. Speed of sound was monitored in horses during the 2007 racing season and compared with the CWIs via regression analysis. Sex, age, limb, and MCIII failure were included as covariates in the model. RESULTS-SOS was significantly associated with CWI(total) at 8 sites and with independent CWIs of the various gaits at all 9 sites. Progression of SOS in MCIIIs with workload differed significantly in horses with clinical signs of metacarpal bone failure, compared with results for horses with clinically normal MCIIIs, in 1 site by use of CWI(total) and in 5 sites by use of the independent CWIs for the various gaits. CONCLUSIONS AND CLINICAL RELEVANCE-These results indicated that SOS in the MCIII of racing Thoroughbreds followed a constant pattern of progression as workload accumulated. With the development of more precise quantitative ultrasonography devices, SOS corrected for amount of activity may be used to identify horses at risk of bone failure.

History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: a study in retired elite gymnasts

BACKGROUND

Female gymnasts frequently present with overt signs of hypoestrogenism, such as late menarche or menstrual dysfunction. The objective was to investigate the impact of history of amenorrhoea on the exercise-induced skeletal benefits in bone geometry and volumetric density in retired elite gymnasts.

SUBJECTS AND METHODS

24 retired artistic gymnasts, aged 17-36 years, who had been training for at least 15 h/week at the peak of their career and had been retired for 3-18 years were recruited. They had not been engaged in more than 2 h/week of regular physical activity since retirement. Former gymnasts who reported history of amenorrhoea ('AME', n=12: either primary or secondary amenorrhoea) were compared with former gymnasts ('NO-AME', n=12) and controls ('C', n=26) who did not report history of amenorrhoea. Bone mineral content (BMC), total bone area (ToA) and total volumetric density (ToD) were measured by pQCT at the radius and tibia (4% and 66%). Trabecular volumetric density (TrD) and bone strength index (BSI) were measured at the 4% sites. Cortical area (CoA), cortical thickness (CoTh), medullary area (MedA), cortical volumetric density (CoD), stress-strain index (SSI) and muscle and fat area were measured at the 66% sites. Spinal BMC, areal BMD and bone mineral apparent density (BMAD) were measured by DXA.

RESULTS

Menarcheal age was delayed in AME when compared to NO-AME (16.4+/-0.5 years vs. 13.3+/-0.4 years, p<0.001). No differences were detected between AME and C for height-adjusted spinal BMC, aBMD and BMAD, TrD and BSI at the distal radius and tibia, CoA at the proximal radius, whereas these parameters were greater in NO-AME than C (p<0.05-0.005). AME had lower TrD and BSI at the distal radius, and lower spinal BMAD than NO-AME (p<0.05) but they had greater ToA at the distal radius (p<0.05).

CONCLUSION

Greater spinal BMC, aBMD and BMAD as well as trabecular volumetric density and bone strength in the peripheral skeleton were found in former gymnasts without a history of menstrual dysfunction but not in those who reported either primary or secondary amenorrhoea. History of amenorrhoea may have compromised some of the skeletal benefits associated with high-impact gymnastics training.

Influence of drop-landing exercises on bone geometry and biomechanical properties in prepubertal girls: a randomized controlled study

We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 girls (Tanner stage 1, 6-10 years old) randomly assigned to control (C), low-drop (LD), or high-drop (HD) exercise groups. The LD and HD groups performed single-leg drop-landings (three sessions/week and 50 landings/session) from 14 and 28 cm, respectively, using the nondominant leg. Single-leg peak ground-reaction impact forces in a subsample ranged between 2.5 and 4.4 times body weight. Dependent variables were bone geometry and biomechanical properties using magnetic resonance imaging. No differences (P > 0.05) were found among groups at baseline for age, stature, lean tissue mass (DXA--Lunar 3.6-DPX), leisure-time physical activity, average daily calcium intake, or measures of knee extensor or flexor torque. A series of ANOVA and ANCOVA tests showed no within- or between-group differences from baseline to posttraining. Group comparisons assessing magnitude of change in side-to-side differences in geometry (area cm(2)) and cross-sectional moment of inertia (cm(4)) at proximal, mid, and distal sites revealed negligible effect sizes. Our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low to moderate peak ground-reaction impact forces do not influence geometrical or biomechanical measures in the developing prepubertal female skeleton.

Targeted exercises against hip fragility

SUMMARY

Compared to high-impact exercises, moderate-magnitude impacts from odd-loading directions have similar ability to thicken vulnerable cortical regions of the femoral neck. Since odd-impact exercises are mechanically less demanding to the body, this type of exercise can provide a reasonable basis for devising feasible, targeted bone training against hip fragility.

INTRODUCTION

Regional cortical thinning at the femoral neck is associated with hip fragility. Here, we investigated whether exercises involving high-magnitude impacts, moderate-magnitude impacts from odd directions, high-magnitude muscle forces, low-magnitude impacts at high repetition rate, or non-impact muscle forces at high repetition rate were associated with thicker femoral neck cortex.

METHODS

Using three-dimensional magnetic resonance imaging, we scanned the proximal femur of 91 female athletes, representing the above-mentioned five exercise-loadings, and 20 referents. Cortical thickness at the inferior, anterior, superior, and posterior regions of the femoral neck was evaluated. Between-group differences were analyzed with ANCOVA.

RESULTS

For the inferior cortical thickness, only the high-impact group differed significantly (approximately 60%, p = 0.012) from the reference group, while for the anterior cortex, both the high-impact and odd-impact groups differed (approximately 20%, p = 0.042 and p = 0.044, respectively). Also, the posterior cortex was approximately 20% thicker (p = 0.014 and p = 0.006, respectively) in these two groups.

CONCLUSIONS

Odd-impact exercise-loading was associated, similar to high-impact exercise-loading, with approximately 20% thicker cortex around the femoral neck. Since odd-impact exercises are mechanically less demanding to the body than high-impact exercises, it is argued that this type of bone training would offer a feasible basis for targeted exercise-based prevention of hip fragility.

The influence of dance training on growth and maturation of young females: A mixed longitudinal study

BACKGROUND

The effects of systematic sports training during childhood and adolescence on subsequent growth and sexual maturation remains in dispute.

AIM

The study aimed to determine whether moderate-high volumes of dance training adversely influence linear growth and sexual maturation of young girls progressing through puberty.

SUBJECTS AND METHODS

This 3-year mixed longitudinal study comprised 82 novice dancers and 61 controls, aged 8-11 years at baseline, who were assessed bi-annually for 3 consecutive years. A biological maturational age was determined by estimating attainment of age at peak height velocity (PHV). Body dimensions were measured by anthropometry, and exercise levels, nutritional intake and age at menarche by questionnaires.

RESULTS

Controls had significantly greater unadjusted height velocity than dancers 1 year before PHV, however there was no difference between groups in age of attainment of PHV. When controlling for maturation, lean mass, fat mass and extracurricular sport (excluding dancing), there were no group differences in absolute growth or velocity of growth in height, sitting height or leg length. Within the dancers there were no effects of years of dancing (>6.5 years) or weekly dance hours (>7 h per week) on growth velocities. No association was found between age at menarche and years or hours of dance training.

CONCLUSION

Results suggest that moderate-high levels of dance training do not affect linear growth and maturation. Thus, girls should not be discouraged from dance participation on the basis of potential growth delays.

The Use of External Transducers for Estimating Bone Strain at the Distal Tibia During Impact Activity

Noninvasive methods for monitoring the in vivo loading environment of human bone are needed to determine osteogenic loading patterns that reduce the potential for bone injury. The purpose of this study was to determine whether the vertical ground reaction impact force (impact force) and leg acceleration could be used to estimate internal bone strain at the distal tibia during impact activity. Impact loading was delivered to the heels of human-cadaveric lower extremities. The effects of impact mass and contact velocity on peak bone strain, impact force, leg acceleration, and computed impact force (leg acceleration∗impact mass) were investigated. Regression analysis was used to predict bone strain from six different models. Apart from leg acceleration, all variables responded to impact loading similarly. Increasing impact mass resulted in increased bone strain, impact force, and computed impact force, but decreased leg acceleration. The best models for bone strain prediction included impact force and tibial cross-sectional area (R2=0.94), computed impact force and tibial cross-sectional area (R2=0.84), and leg acceleration and tibial cross-sectional area (R2=0.73). Results demonstrate that when attempting to estimate bone strain from external transducers some measure of bone strength must be considered. Although it is not recommended that the prediction equations developed in this study be used to predict bone strain in vivo, the strong relationship between bone strain, impact force, and computed impact force suggested that force platforms and leg accelerometers can be used for a surrogate measure of bone strain.