Browsing by Subject "pQCT"

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    Bone mass, estimated strength and Kinetic changes in collegiate and post-collegiate runners with a history of stress fracture.
    (2009-08) Popp, Kristin Lynn
    Purpose: To determine differences in bone geometry, estimates of bone strength, muscle size, bone strength relative to load, and running kinetics, in female runners with and without a history of stress fractures. Methods: A total of 32 competitive distance runners aged 18-35, with (SFX, n = 16) or without (NSFX, n = 16) a history of stress fracture were recruited for this cross-sectional study. Peripheral Quantitative Computed Tomography (pQCT, Orthometrix XCT 2000) was used to assess volumetric bone mineral density (vBMD, mm3), bone area (ToA, mm2), and estimated compressive bone strength (bone strength index; BSI= ToA * ToD2) at the distal tibia (4%). Total (ToA, mm2) and cortical (CoA, mm2= ToA * ToD2) bone area, cortical vBMD, and estimated bending strength (strength strain index; SSIp, mm³) were measured at the 15%, 25%, 33%, 45%, 50% and 66% sites. Participants completed a fatigue run on an instrumented treadmill. GRF's were assessed throughout the run and used in conjunction with pQCT measurements to estimate bone strength relative (cm2) to load at all cortical sites (15%-55%). Results: Bone strength was significantly lower in the SFX group at the mid-upper (45-66% sites) tibia for SSIp (-7-10%). Differences in strength were due to smaller cortical bone area (-6-7%) while total bone area and vBMD were not different at any site. The SFX group also had lower bone strength relative to GRF at the 45% (-12%), 50% (-17%) and 66% (-11%) sites. Peak vertical (Z) GRF's in the SFX group were approximately 5% higher on both legs compared to the NSFX group. Peak breaking force also tended to be higher (0.5%-3.8%) in the SFX group. Propulsion forces were 8-14% in the SFX group compared to the NSFX group, while peak lateral forces were 14.9-32.5% higher. Conclusion: These findings suggest that bone CoA and strength are lower in the middle 1/3 of the tibia in runners with a history of stress fracture. Bone strength relative to load was also lower in this same region suggesting that strength deficits in the middle 1/3 of the tibia indicate higher stress fracture risk. Additionally, our trends indicate that there are several kinetic variables that may be important in predicting stress fracture risk. However, further research is needed to confirm these findings.
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    Comparison of tibial geometry, density and strength between adult female dancers, gymnasts and runners
    (2014-02) Bellard Freire Ribeiro, Ana Cristina
    Physical activity has a site-specific osteogenic effect that is known to positively improve bone health (Schoenau, 2006, Greene, 2006, Uusi-Rasi, 2006). The effect of dancing on bone health has received sparse attention and the extent of the osteogenic effect of dancing is not known. Given that dancing may be considered a medium impact activity, one would expect that the magnitude of its osteogenic effect might be between those of high impact activities such as gymnastics and cyclic low impact activities like running with the most pronounced effects in the weight bearing bones such as the tibia and femur. Thus, the purpose of this study is to compare the osteogenic effects of dance, gymnastics and middle/long-distance running in adult females, as measured by tibial geometry, density, and strength. Methods: Eleven dance majors and eleven collegiate gymnasts (ages 18-22) were recruited for the study. Runner (n=22) and control (n=19) data were obtained from the UM Laboratory of Musculoskeletal Health database (Smock et al., 2009 and Bruininks, 2009). The control subjects were young adult, sedentary females. Total cross-sectional area (ToA) was measured by peripheral quantitative computed tomography (pQCT) at the tibia (4% and 66% from its distal end); total volumetric bone mineral density (vBMD) and bone strength index (BSI) were measured at the 4% site. Polar strength-strain index (SSIp) was measured at the 66% site. Results: After controlling for height and body mass, the distal and proximal cross-sectional areas of the tibia (ToA 4%, ToA 66%) and SSIp did not differ significantly between groups. However, total vBMD was significantly higher for dancers and gymnasts when compared to controls (p=0.01 and p=0.02, respectively). In addition, BSI was significantly higher for dancers, gymnasts, and runners when compared to controls (p=0.001, p<0.001, and p=0.03, respectively). Participants did not differ in age, weight or tibial length, assuring that the samples were not biased with respect to age and anthropometrics.Conclusion:The current results suggest that dance and gymnastics have the greatest osteogenic effects at the tibia in eumenorrheic adult females, followed by middle-long distance running, when compared to sedentary healthy controls.