Lumbar spine bone mineral adaptation: cricket fast bowlers versus controls.

Elite adult male fast bowlers have high lumbar spine bone mineral, particularly on the contralateral side to their bowling arm. It is thought that bone possesses its greatest ability to adapt to loading during adolescence, but it is unknown at what age the greatest changes in lumbar bone mineral and asymmetry develops in fast bowlers. Objectives: This study aims to evaluate the adaptation of the lumbar vertebrae in fast bowlers compared to controls and how this is associated with age. Methods: 91 male fast bowlers and 84 male controls aged 14-24 years had between one and three annual anterior-posterior lumbar spine dual-energy-X-ray absorptiometry scans. Total (L1-L4) and regional ipsilateral and contralateral L3 and L4 (respective to bowling arm) bone mineral density and content (BMD/C) were derived. Multilevel models examined the differences in lumbar bone mineral trajectories between fast bowlers and controls. Results: At L1-L4 BMC and BMD, and contralateral BMD sites, fast bowlers demonstrated a greater negative quadratic pattern to their accrual trajectories than controls. Fast bowlers had greater increases in BMC in L1-L4 between 14 and 24 years of 55% compared with controls (41%). Within vertebra, asymmetry was evident in all fast bowlers and increased by up to 13% in favour of the contralateral side. Conclusions: Lumbar vertebral adaptation to fast bowling substantially increased with age, particularly on the contralateral side. The greatest accrual was during late adolescence and early adulthood, which may correspond with the increasing physiological demands of adult professional sport.

Lumbar bone stress injuries and risk factors in adolescent cricket fast bowlers.

Cricket fast bowling is associated with a high prevalence of lumbar bone stress injuries (LBSI), especially in adolescent bowlers. This has not been sufficiently explained by risk factors identified in adult players. This study aimed to examine the incidence of LBSI in adolescent fast bowlers over a prospective study and potential risk factors. Forty asymptomatic male fast bowlers (aged 14-17 years) received baseline and annual lumbar dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) scans, and musculoskeletal and bowling workload assessment; 22 were followed up after one year. LBSI prevalence at baseline and annual incidence were calculated. Potential risk factors were compared between the injured and uninjured groups using T-tests with Hedges' g effect sizes. At baseline, 20.5% of participants had at least one LBSI. Subsequent LBSI incidence was 27.3 ± 18.6 injuries per 100 players per year (mean ± 95% CI). Injured bowlers were older on average at the beginning of the season preceding injury (16.8 versus 15.6 years, g = 1.396, P = 0.047). LBSI risk may coincide with increases in bowling workload and intensity as bowlers step up playing levels to more senior teams during late adolescence whilst the lumbar spine is immature and less robust.

Lumbar Bone Mineral Adaptation: The Effect of Fast Bowling Technique in Adolescent Cricketers.

INTRODUCTION: Localized bone mineral density (BMD) adaptation of the lumbar spine, particularly on the contralateral side to the bowling arm, has been observed in elite male cricket fast bowlers. No study has investigated this in adolescents, or the role of fast bowling technique on lumbar BMD adaptation. This study aims to investigate lumbar BMD adaptation in adolescent cricket fast bowlers, and its relationship with fast bowling technique. METHODS: Thirty-nine adolescent fast bowlers underwent anteroposterior dual x-ray absorptiometry scan of their lumbar spine. Hip, lumbopelvic and thoracolumbar joint kinematics, and vertical ground reaction kinetics were determined using three-dimensional motion capture and force plates. Significant partial (covariate: fat-free mass) and bivariate correlations of the technique parameters with whole lumbar (L1-L4) BMD and BMD asymmetry (L3 and L4) were advanced as candidate variables for multiple stepwise linear regression. RESULTS: Adolescent fast bowlers demonstrated high lumbar Z-Scores (+1.0; 95% confidence interval [CI], 0.7-1.4) and significantly greater BMD on the contralateral side of L3 (9.0%; 95% CI, 5.8%-12.1%) and L4 (8.2%; 95% CI, 4.9%-11.5%). Maximum contralateral thoracolumbar rotation and maximum ipsilateral lumbopelvic rotation in the period between back foot contact and ball release (BR), as well as contralateral pelvic drop at front foot contact, were identified as predictors of L1 to L4 BMD, explaining 65% of the variation. Maximum ipsilateral lumbopelvic rotation between back foot contact and BR, as well as ipsilateral lumbopelvic rotation and contralateral thoracolumbar side flexion at BR, were predictors of lumbar asymmetry within L3 and L4. CONCLUSIONS: Thoracolumbar and lumbopelvic motion are implicated in the etiology of the unique lumbar bone adaptation observed in fast bowlers whereas vertical ground reaction force, independent of body mass, was not. This may further implicate the osteogenic potential of torsional rather than impact loading in exercise-induced adaptation.

Reproducibility of bone age assessment from DXA hand scans: expert versus novice.

Dual-energy x-ray absorptiometry (DXA) scans are frequently used in human biological research to study bone health and body composition. Hand-wrist scans for the assessment of skeletal maturity can also be easily obtained in immature research participants who are being scanned to assess bone health. Whilst assessment by an expert is the desired arrangement such expertise may not be available, and thus knowledge of the relative reproducibility of a trained novice and an acknowledged expert is pertinent. Here we compare the relative reproducibility of an expert and a trained novice on 41 DXA left-hand scans of adolescent males using the Tanner-Whitehouse 3 (TW3) RUS method. The trained novice showed almost perfect reproducibility when evaluating bone age from DXA hand scans compared to an expert in skeletal maturity assessment. Both observers demonstrated reproducibility good enough to suggest that the TW3 method is appropriate to use with DXA hand scans by a trained researcher.