Playing soccer is associated with higher BMD of the skeleton at all sites measured. Running is associated with higher BMD at directly loaded sites (the calcaneus) but not at relatively unloaded sites (the spine). Specific loading conditions, seen in ball sports or in running, play a pivotal role in skeletal adaptation. The importance of including an appropriate control group in clinical studies is underlined.

Within the limitations of our study involving the testing of 1 type of screw purchase in ovine tibiae, results demonstrate that clinical levels of lag screw tightening (86% Tmax) are past the yield point of bone. Tightening to these high torque levels can cause damage leading to compromised holding strength. Further research is still required to establish the appropriate level of torque required for achieving optimal fracture fixation and healing.

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HUTCHINSON, T. M., R. T. WItALEN, T. M. CLEEK, J. M. VO-GEL, and S. B. ARNAUD. Factors in daily physical activity related to calcaneal mineral density in men. Med. Sci. Sports Exert., Vol. 27, No. 5, pp. 745-75(i, 1995. To determine the factors in daily physical activity that influence the mineral density of the calcaneus, we recorded walking steps and the type and duration of exercise in 43 healthy 26-to 51-yr-old men. Areal (g-cm 2) calcaneal bone mineral density (CBMD) was measured by single energy x-ray densitometry (SXA, Osteon, Inc., Wahiawa, HI). Subjects walked a mean (_+SD) of 7902 ('+_2534)steps per day or approximately 3.9 (+-1.2) miles daily. Eight subjects reported no exercise activities. The remaining 35 subjects spent 143 (2-772) (median and range) min.wk _ exercising. Twenty-eight men engaged in exercise activities that generate single leg peak vertical ground reaction forces (GRF:_) of 2 or more body weights (high loaders, HL), and 15 reported exercise or daily activities that typically generate GRFL less than 1.5 body weights (low loaders, LL). CBMD was 12% higher in HI_, than LL ((I.668 + 0.074 g.cm -2 vs (I.597 +_ 0.062 g.cm -, P < 0.004). In the HL group, CBMD correlated to reported minutes of high load exercise (r = 0.41, P < 0.03). CBMD was not related to the number of daily walking steps (N = 43, r = 0.03, NS). The results of this study support the concept that the dominant factor in daily physical activity relating to bone mineral density is the participation in site specific high loading activities, i.e., for the calcaneus, high calcaneal loads.

'This is the peer reviewed version of the following article: Ryan MK, Mohtar AA, Cleek TM, Reynolds KJ. Time-elapsed screw insertion with microCT imaging. Journal of Biomechanics. pii: S0021-9290(15)00727-7.