INTRODUCTION: Despite exercise being prescribed to benefit bone health [1], little is known about the specific external loading characteristics of exercise required to promote bone accrual. It Is not known how limb specific loading variables are associated with bone characteristics. We aimed to assess if quantified external loading is associated with tibial bone characteristics in elite cricketers and football players. METHODS: Eleven professional cricketers (right-arm fast bowlers) and eighteen professional footballers (outfield) were monitored with Inertial Measurement Units placed on the anteromedial tibia at 14% of the distal length during a standardised training session. Six competitive overs for cricketers and a warm-up for footballers (hopping, sprinting, cutting) were performed. Peak tibial acceleration, peak positive acceleration (PPA), cumulative load and relative load were calculated as loading variables. Whole-body dual-energy x-ray absorptiometry (DEXA) and tibial peripheral computed tomography (pQCT; 4%, 14%, 38% and 44% of the tibial length) scans were performed on each leg to retrieve bone characteristics. Paired sample t-tests were performed on all variables between legs in each group. Correlations were performed between loading variables and bone characteristics for both groups. RESULTS: Cricketers showed greater left leg external load variables (peak acceleration (+91 g, +53%) and PPA (+59 g, +38%)) than the right leg (p<0.001). The left leg of cricketers showed greater bone characteristics derived from DEXA (leg bone mass (+0.86 kg, +12%), relative leg mass (+0.78, +5%), total BMD (+0.08 g/cm2), leg BMC (+82 g; p<0.028)) and pQCT (bone mass (+0.22 kg, +4%), periosteal circumference (38% site; +2.07 mm, +2%) torsional strength (14% site; +214 mm3, +7%; p<0.035), and axial strength (14% site; +39 mm3, +3%: 38% site; (+111 mm3, +7%)) than the right leg. There were no differences between legs in football players or correlations between loading variables and bone characteristics in either group. CONCLUSION: The greater bone characteristics in the left leg during a fast-bowling action may be reflective of the higher left leg loads experienced. No correlations were shown between loading and bone in either group, this likely to be due to factors, such as load frequency, which is known to influence bone accrual [2]. The unilateral aspect of cricket fast bowling causes the planting leg to experience consistently higher loads than the other leg, likely explaining the differences in bone between limbs. The bilateral movement patterns of football likely explain the lack of differences in this group.
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