Peripheral QCT sector analysis reveals early exercise-induced increases in tibial bone mineral density

Objectives: The purpose of this controlled trial was to determine whether subtle changes in mineralization and geometry of the tibia were evident following short term exercise interventions. Methods: Fifty-seven female volunteers (age 20.1?1.6) were randomized to one of four, 13-week training groups: sedentary control, resistance training, aerobic training, or combined aerobic-resistance. A pQCT image analysis software was developed and used to analyze images taken at sites 4%, 38% and 66% from the distal tibia at baseline and at completion of training. Parameters of bone mineral density, geometry and strength were determined for the entire scan cross-section and for each of six 60(o) polar sectors. Repeated-measures ANOVA and Fisher's LSD post hoc tests analyzed the effects of training over time. Results: Trabecular density (TrDn) at the 4% site increased from 279.8?37.1 to 283.1?36.0 mg/cm(3) in the aerobic group, and from 285.1?24.6 to 287.5?22.9 mg/cm(3) in the combined group over the study period (P≤0.001). Regional sector analyses revealed that impact exercises resulted in localized changes to the medial aspect of the tibia. Small increases in total bone area were observed in the diaphysis (38% site) (P<0.05). Conclusions: Subtle, regional increases in trabecular density may be an early measurable manifestation of bone quality changes.