Introduction:​ Musculoskeletal development in the upper limbs of non-elite female gymnasts during pre and early pubescent growth is under researched. Most studies have focussed on elite rather than non-elite gymnasts, via dual-energy X-ray absorptiometry (DXA). The purpose of this thesis was to longitudinally characterise the effects of non-elite female artistic gymnastics participation on upper limb musculoskeletal parameters using peripheral Quantitative Computed Tomography (pQCT), DXA and muscle function assessments.

Three major studies were designed. Study one compared the upper limb of two groups of gymnasts (high-training gymnasts (HGYM), participating in 6-16 hr/wk, low-training gymnasts (LGYM), participating in 1-5 hr/wk) and an age matched control group (NONGYM) for differences in bone mass, size and strength. Difference in upper limb muscle size, structure and function were also compared. Study two pooled both HGYM and LGYM to compare traditional pQCT skeletal parameters at the radius (4% and 66% sites) with NONGYM. To advance the understanding of site and bone specificity in young gymnastics, similar measures were also undertaken at the ulna. Study three combined variables in studies one and two in a longitudinal (6-month) comparison of the upper limb musculoskeletal changes in two groups of gymnasts (HGYM, LGYM) and a NONGYM group. Benefits beyond growth associated with gymnastics participation during pre- and early pubertal years were examined.

Methods:​ Ninety-one girls (age 6 to 12 years, Tanner stage 1 to 3) participated in the study. Total body DXA scans assessed body composition (lean mass and fat mass) as well as the skeletal parameters of total body and arms, bone mineral content (BMC) and bone mineral density (BMD). Peripheral QCT was used to assess BMC, total and trabecular density (ToD, TrD), bone strength (BSI, SSI), total and cortical area (ToA, CoA) of the non-dominant radius and ulna at the 4% and 66% sites. Muscle cross sectional area (MCSA) was also obtained from pQCT. Muscle function was assessed with generic tests for strength, explosive power and endurance.

Results:​ At baseline, results from weight adjusted ANCOVA showed HGYM had greater radial bone strength than NONGYM as well as greater arm lean mass, BMC and muscle function (+5 to +103%, p<0.05). LGYM displayed greater arm lean mass, BMC (DXA), explosive power and endurance than NONGYM (+4% to +46%, p<0.05). Differences in bone strength between LGYM and NONGYM did not reach significance. HGYM showed larger skeletal differences with NONGYM than LGYM, yet differences between the two groups of gymnasts were not significant. At the 4% forearm, the gymnastics-induced skeletal benefits were greater at the radius than ulna (Z-scores for BMC, TrD and BSI +0.40 to +0.61 SD, p<0.05 vs. +0.15 to +0.48 SD, NS). At the 66% forearm, skeletal benefits were greater at the ulna than the radius (Z-scores for BMC, ToA, CoA, SSI +0.59 to +0.82 SD, p<0.01 vs. +0.35 (ToA) and +0.43 SD (SSI), p<0.01).

Longitudinal results showed both groups of gymnasts had increased ToD at the 4% radius as well as bone mass, area and strength at the 66% forearm compared with NONGYM (LGYM +6 to +18%, HGYM +6 to +25%, p<0.05). HGYM had increased BMC and BSI (4% radius) as well as CoA and ToD (66% ulna) and MCSA compared with LGYM (+7 to +28%, p<0.05). HGYM had the greatest skeletal gains over the six month period at the 4% radius. Despite NONGYM showing the greatest improvement in most muscle function tests after the six months, gymnasts’ muscle function remained superior.

Conclusion:​ At baseline, non-elite gymnastics participation was associated with musculoskeletal benefits in upper limb bone geometry, strength and muscle function. However, differences between the two gymnastics groups did not emerge. Positive skeletal associations for gymnasts compared with NONGYM were greater when the radius and ulna were combined. Following six months of growth and non-elite gymnastics participation HGYM showed greatest increases at the 4% radius. While differences between LGYM and NONGYM emerged, HGYM clearly had the greatest skeletal benefits, irrespective of bone and site. Unlike baseline results, pQCT differences in upper limb skeletal parameters between HGYM and LGYM, and LGYM and NONGYM were apparent following longitudinal analysis. Gymnasts, independent of training hours, consistently displayed superior muscle function although, with growth, non-gymnasts’ muscle function improved. Musculoskeletal benefits beyond growth exist following nonelite gymnastics participation during early puberty.