Pre-menarcheal physical activity predicts post-menarcheal lean mass and core strength, but not fat mass.

OBJECTIVES: Youth exercise is associated with improved body composition, but details regarding timing and persistence are limited. We examined pre- and circum-menarcheal organized physical activity exposure (PA) as a factor in development of early post-menarcheal lean mass, fat mass and muscle strength. METHODS: Participants in a longitudinal study of musculoskeletal growth using dual energy X-ray absorptiometry (DXA) were included based on: 1) Whole body DXA scans: 0.5-1.5 years pre-menarche, 0.5-1.5 years post-menarche; 2) PA records for ⋝6 months preceding the first DXA (prePA) and for the inter-DXA interval (circumPA). Dominant arm grip strength and sit-ups tests coincided with DXA scans; PA, height and maturity were recorded semi-annually. Regressions correlated PA with lean mass/fat mass/strength, accounting for maturity, body size, and baseline values. RESULTS: Seventy girls [baseline: 11.8 yrs (sd 1.0), follow-up: 13.9 years (sd 1.0)] demonstrated circum-menarcheal gains of 25-29% for lean and fat mass and 33% for grip strength. PREPA correlated with pre- and post-menarcheal lean mass, sit-ups and pre-menarcheal fat mass (p<0.05), but not grip strength. CIRCUMPA correlated with only post-menarcheal sub-head lean mass (p=0.03). CONCLUSIONS: Lean mass and core strength at 1-year post-menarche were more strongly predicted by pre-menarcheal organized PA than by recent circum-menarcheal PA.

Arm bone loading index predicts DXA musculoskeletal outcomes in two samples of post-menarcheal girls.

OBJECTIVE: A site-specific bone loading index was developed to predict post-menarcheal arm bone mass, geometry, areal density and non-bone lean mass using organized activity records. METHODS: Two cohorts of post-menarcheal girls (A= 55, B= 48) met analysis inclusion criteria: (1) Whole body and non-dominant radius DXA scans +1.0 to +2.6 years post-menarche; (2) detailed, organized activity records available for 36 months prior to the focal DXA scan; (3) accompanying anthropometric data. DXA non-dominant arm and radius regions of interest (1/3, Ultradistal (UD)) were evaluated. An arm bone loading index (arm totBLI) was developed and refined to describe >50 activities. Separate regression analyses for Cohorts A&B tested explanatory value of arm totBLI for DXA outcomes, accounting for gynecological age, height and whole body non-bone lean mass. RESULTS: In both cohorts, arm totBLI reflecting 3 years of peri-menarcheal activity exposure exhibited strong explanatory value for post-menarcheal radius and arm outcomes (squared semi-partial r =0.07-0.34, p<0.05), except Arm Area. For both cohorts and most outcomes, arm totBLI explained significant variance, even after adjusting for local muscle mass. CONCLUSIONS: In two independent cohorts, arm totBLI may consistently indicate osteogenic and sarcogenic properties of represented activities; additional research is necessary for further refinement and validation.

Distal radius geometry and skeletal strength indices after peripubertal artistic gymnastics.

UNLABELLED: 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.

Sustained skeletal benefit from childhood mechanical loading.

SUMMARY: Preliminary prospective, longitudinal results suggest that pre-menarcheal exposure to artistic gymnastics is associated with greater radius BMC, aBMD, and projected area throughout growth and into early adulthood, more than 4 years after activity cessation. Any loss of benefit associated with de-training appears to be temporary. INTRODUCTION: Mechanical loading may enhance bone accrual during growth, but prospective evidence of benefit retention is limited. This prospective, longitudinal cohort study tests whether gymnastics is linked to distal radius advantages during growth and four or more years post-training cessation. METHODS: Semi-annually, female ex/gymnasts and non-gymnasts underwent height and weight measurements; questionnaires assessed calcium intake, physical activity, and maturation. Annual dual energy X-ray absorptiometry scans (Hologic QDR 4500W) measured total body fat-free mass, skull areal density (aBMD), and bone mineral content (BMC); forearm scans measured ultradistal and 1/3 radius area, BMC, and aBMD. Analysis inclusion criteria were: (1) achievement of gynecological age >4 years and (2) for gymnasts, >2 years of pre-menarcheal training (>6 h/week), ceasing between 0.5 year pre-menarche and 1 year post-menarche. Hierarchical linear modeling (HLM v6.0) evaluated outcomes for ex/gymnasts versus non-gymnasts; a slope/intercept discontinuity evaluated de-training effects. RESULTS: Data from 14 non-gymnasts and six ex/gymnasts represented outcomes from 4 years pre-menarche to 9 years post-menarche. All adjusted distal radius parameters were higher in ex/gymnasts than non-gymnasts (p < 0.02). Ultradistal BMC, ultradistal aBMD, and 1/3 aBMD temporarily decreased with gymnastic cessation (p < 0.04); ultradistal area, 1/3 area, and 1/3 BMC did not change significantly. Skull outcomes did not differ between groups or change with activity cessation. CONCLUSION: Gymnastic exposure during childhood and early puberty is associated with greater radius bone mass, size, and aBMD. Despite brief de-training losses in density and mass, significant skeletal benefits are manifested throughout growth and at least 4 years beyond activity cessation into early adulthood.

Skeletal geometry and indices of bone strength in artistic gymnasts.

This review addresses bone geometry and indices of skeletal strength associated with exposure to gymnastic loading during growth. A brief background characterizes artistic gymnastics as a mechanical loading model and outlines densitometric techniques, skeletal outcomes and challenges in assessment of skeletal adaptation. The literature on bone geometric adaptation to gymnastic loading is sparse and consists of results for disparate skeletal sites, maturity phases, gender compositions and assessment methods, complicating synthesis of an overriding view. Furthermore, most studies assess only females, with little information on males and adults. Nonetheless, gymnastic loading during growth appears to yield significant enlargement of total and cortical bone geometry (+10 to 30%) and elevation of trabecular density (+20%) in the forearm, yielding elevated indices of skeletal strength (+20 to +50%). Other sites exhibit more moderate geometric and densitometric adaptations (5 to 15%). Mode of adaptation appears to be site-specific; some sites demonstrate marked periosteal and endosteal expansion, whereas other sites exhibit negligible or moderate periosteal expansion coupled with endocortical contraction. Further research is necessary to address sex-, maturity- and bone tissue-specific adaptation, as well as maintenance of benefits beyond loading cessation.

Muscle indices do not fully account for enhanced upper extremity bone mass and strength in gymnasts.

OBJECTIVES: Muscular forces are an important determinant of bone strength, but bone may also adapt to non-muscular loading. We tested the hypothesis that loads associated with childhood gymnastics yield high arm bone mass (BMC), bone size and bone strength, independent of arm lean mass (FFM) and muscle cross-sectional area (CSA). METHODS: Total body DXA and distal radius pQCT scans were performed on 33 post-menarcheal girls (19 ex/gymnasts, 14 non-gymnasts). Physical activity and calcium intake were assessed by questionnaire. For the non-dominant arm, pQCT measured bone strength indices and bone CSA (total, cortical) (4%, 33% sites); DXA measured arm FFM, arm BMC and skull BMC. Multiple regression analyses assessed gymnastic exposure, arm FFM, gynecological age and stature as predictors of bone parameters. RESULTS: Bone outcomes at loaded upper extremity sites were 10-42% greater in ex/gymnasts than non-gymnasts. Gymnastic exposure remained a consistent, significant predictor of upper extremity skeletal parameters after accounting for the effects of muscle parameters, gynecological age and height. CONCLUSIONS: Considering the effects of either arm FFM or muscle CSA, indices of bone mass, geometry and theoretical strength are disproportionately elevated after gymnastic exposure. Thus, non-muscular loading may be a distinct and important determinant of human skeletal structure.