Gender Differences in Bone Adapting to Endurance Training in Wistar Rats

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PURPOSE: To investigate the gender differences in bone material properties adapting to endurance training. METHODS: Wistar rats (7 weeks old) were randomly divided to male and female control groups (MCON and FCON, n=10 for each) and male and female exercise groups (MEXE and FEXE, n=11 for each). Animals in exercise groups subjected to an 8-week endurance running training with a protocol of 15 ∼ 28m/min, 60min/day and 5days/week. Two-way (gender×exercise) ANOVA was used for statistical analysis (α=.05). RESULTS: Significant main effects in gender (p<.001) and exercise (p<.001) were shown in body weight (BW), that male rats were higher than female rats (382.8±5.8 vs. 282.6±5.9 g) and exercise rats were lower than non-exercise rats (316.1±5.8 vs. 349.3±6.0 g).Simple main effects analysis showed that only the MEXE group was significantly lower in BW than the MCON group (353.5±8.0 vs. 412.1±8.4). In biomaterial properties, femora of male rats were significantly higher in yield load (YL, 217±4.9 vs. 147.6±4.9 N), ultimate load (UL, 249.2±6.0 vs. 165.2±6.0 N), yield load energy (YL energy, 54.5±2.1 vs. 37.3±2.1 mJ), ultimate load energy (UL energy, 100.8±4.9 vs. 68.3±4.9 mJ), post-yield energy (PY energy, 46.3±4.7 vs. 31.0±4.7 mJ) and stiffness (529.2±20.7 vs. 385.6±20.7 mm/N) as compared to female rats. Conversely, after eliminating the factor of tissue size, male rats were significant lower in yield stress (YS, 151.8±3.9 vs. 183.4±3.9 MPa) and Young's modulus (4.9±0.3 vs. 7.7±0.3 GPa). In the main effects for exercise, exercise rats were lower than control rats in CSMI (12.3±0.6 vs. 14.4±0.6 mm4), cortical area (7.4±0.2 vs. 8.1±0.2 mm2), YL (174.9±4.9 vs. 189.8 .(N 6.0±215.9.vs 6.0±198.5)UL,(N 4.9±3.0±58.8.vs 3.0±50.2)Simple main effect analysis showed that YL energy was significant lower in the MEXE group as compared to the MCON group 0.1±7.0)and phosphorous (dl/mg 0.1±10.2.vs 0.1±8.8)Serum calcium.(mJ vs. 6.4±0.1 mg/dl) were significantly lower and higher in male rats, respectively. In histomorphometry, male rats showed significantly lower bone volume ratio (17.0±1.2 vs. 20.7±1.1%) but higher trabecular thickness (110.6±1.6 vs. 40.8±1.5μm). CONCLUSIONS: Bone material properties adapting to endurance training were gender-dependant without showing disturbances in status of bone metabolism.