Dose Related Association of Impact Activity and Bone Mineral Density in Pre-pubertal Girls

Abstract

Impact activity is an important contributor to bone accrual. Children engaging in such activity have been shown to have greater bone mineral density (BMD) than their peers. This cross-sectional study was designed to quantify the association between BMD and impact activity in pre-pubescent girls, specifically examining for a dose-dependent relationship. Fifty 7-11-year-old Caucasian female gymnasts were grouped by hours of gymnastics participation during a 6-month period: LOW, 1-8 hours/week (hrs/wk); HIGH, >8 hrs/wk. They were compared with 20 controls, with height, weight, age, and Tanner stage averages matched to the gymnasts. Total body, forearm, hip, lumbar spine BMD, and body composition were measured by dual energy X-ray absorptiometry (DXA). Strength was measured by one repetition maximum testing, calcium intake was quantified by questionnaire, and physical activity was measured by questionnaire and activity monitors. Total and regional BMD were greater in the HIGH group than the controls (P<0.05). Furthermore, both total and forearm BMD were greater in the HIGH group than in the LOW group, and greater in the LOW group than in the controls (P<0.05). Simple regression analysis between hrs/wk of gymnastics activity versus total and regional BMD (using maturation-adjusted Z scores) yielded a positive slope for each site. R2 was greatest for hip BMD (R2 = 0.25), and least for lumbar spine (R2 = 0.10) (P<0.0001). In conclusion, in this group of pre-pubescent girls, we observed a dose-dependent relationship between BMD and hrs/wk of impact activity; even moderate doses of impact activity were associated with increased BMD.

Bone Geometry, Density, and Strength Indices of the Distal Radius Reflect Loading via Childhood Gymnastic Activity

“…Many studies have identified higher aBMD in gymnasts than non-gymnasts at the forearm and other weight-bearing sites (15)(16)(17)(18)(19)(20); only one has explored the relative contributions of geometry and volumetric density (11). Previous analyses by our group demonstrated significantly higher areal BMD at the forearm in premenarcheal gymnasts relative to maturitymatched non-gymnasts; these differences persisted after adjustment for age, height and total body FFM (15).…”

“…Non-Caucasian subjects were excluded from analyses, as there were insufficient numbers to account for racial variation. Gymnasts were included if they trained for at least 6 hours per week (hrs/wk) in the 2-year period prior to measurement, based upon a previous study (16). Following these criteria, 28 gymnasts and 28 non-gymnasts were evaluated.…”

Non-elite gymnastics participation is associated with greater bone strength, muscle size, and function in pre- and early pubertal girls

“…Moreover, a relationship between greater muscle power and higher bone density in adolescent gymnasts has been described [17]. Few studies have directly assessed true measures of muscle function in combination with bone strength in young non-elite gymnasts [8,9]. The extent to which non-elite level participation in gymnastics influences upper body musculoskeletal health is under researched.…”

“…Few studies have assessed the effects of non-elite gymnastics on bone mineral density [7][8][9][10]. Despite reports of significant skeletal benefits, there was a reliance on dual-energy X-ray absorptiometry (DXA) to assess areal bone density.…”

Ward's area location, physical activity, and body composition in 8- and 9-year-old boys and girls

“…(28,29) Physical activity and body composition are important determinants of bone mass, geometry, and strength of the femoral neck. (30)(31)(32)(33)(34) It is reasonable to assume that mechanisms connecting physical activity and body composition to bone mass are also linked to structural adaptation, that is, redistribution of bone mass. As a weight-bearing bone, the femur is particularly stimulated during locomotion movements that affect different diverse areas of the bone.…”