Effects Of Exercise On Bone Mineral Density And Bone Biomechanics In Senile Osteoporosis Mice (SAMP6)

Objective:The aim of this study was to analysis the exercise effects on bone intensity andbone biomechanical of senile osteoporosis mice, and to explore the effects ofpreventing and treating senile osteoporosis.Materials and Methods:Materials and grouping: Eighty-eight senescence accelerated mice(SAMP6) wererandomly divided into8groups, including ten for control group1(C1)withone-month-age, ten for control group2(C2)with two-month-age, ten for low-intensityexercise group1(L1) with one-month-age, ten for low-intensity exercise group2(L2)with two-month-age, ten for medium-intensity exercise group1(M1) withone-month-age, twelve for medium-intensity exercise group2(M2) withtwo-month-age, twelve for high-intensity exercise group1(H1) with one-month-age,twelve for high intensity exercise group2(H2) with two-month-age. The mice of eachexercise group were executed for detection after respectively training one month、twomonths. Twenty normal senescence mouse (SAMP1) with the same age were selectedas homologous control groups: ten for group R1with one-month-age (R1), ten forgroup R2with two-mouth-age (R2). The homologous control groups were executedfor detection after regular feeding one month、 two months. All the above mice, maleand female each half, were housed separately. Each exercise group respectively tooktreadmill training lasting one or two months, the previous six consecutive days fortraining and later one day off in each week. The protocol was respectively continuefor one month and two months. The control group of SAMP6and SAMP1didn’t doany training, all the groups of mice were feeding in the same environment.Treadmill training program：At the beginning, all the three exercise groups took a8m/min intensity adaptive training for six days, each day10min. After the first week,low intensity、medium-intensity and high-intensity groups respectively started runningat beginning speed18m/min、12m/min and8m/min, each day run20mins and thetreadmill，s gradient was0°. And during the second week, the speeds ofhigh-intensity group and medium-intensity group were respectively increased by3m/min every other day, and the duration of all the three exercise groups wereincreased by10mins every other day. During the third week, the speeds of low intensity、medium-intensity and high-intensity group were respectively increased to8m/min、18m/min and28m/min, with duration of50mins per day and5°gradient.Every week the mice run six days with respective strength, group one-month trainedfour weeks and group two-month trained eight weeks.Test methods: All of the mice were executed by collecting eyeball blood, thenimmediately took out the bilateral femur for the bone mineral density and bonebiomechanical detection. The right femoral bone mineral densities were detected byOsteocore3Digital2D (dual-energy X-ray), and the left femoral bone biomechanicalindicators were measured by microcomputer control electron universal testingmachines.Statistical methods: The experimental results were expressed as means±standard deviation (x±s), and the data between groups was tested with single-factoranalysis of variance used SPSS17.0statistical software.Results:1. Weight: The forth week，s weights of group R1、L1and M1significantly increasedcomparing with the basic value(week0). From week4to week8, the weights ofgroup R2and L2were heavier than week0. From week3to week8, the weight ofgroup M2was heavier than week0. The weight of group H2gradually droppedfrom week4, it was lower than group R2and M2that have the same weeks.2. BMD: The femur bone densities of group C1and C2were respectively lower thangroup R1and R2, group L1and M1were higher than group C1, group M2washigher than group C2, group H2was lower than group C2, group H2was lowerthan group H1and L2.3. Bone biomechanical:3.1Yield Stress: The femur bending strengths of group C1and C2wererespectively lower than group R1and R2, group M1and H1were higher thangroup C1, group L2、M2and H2were higher than group C2, group L2washigher than group L1and H2.3.2Max. Load：The femur maximum load of group L2and M2were higher thangroup C2, group M2was higher than group R2、H2.3.3Elastic Modulus: The femur elasticity moduli of group C1and C2wererespectively lower than group R1and R2, group R1and M1were higher thangroup C1, group R2、L2and M2were higher than group C2, group M1washigher than group L1and H1, group M2was higher than group H2, group H1 and H2were respectively lower than group R1and R2, group H2was lower thangroup H1.3.4Cross-sectional Area: The femur transection area of group R2、L2、M2and H2were lower than group R1, group C1、L1and M1were higher than group R2,group H2was lower than group C1、C2and R1.Conclusion:1. Low and medium intensity exercise training can make the senile osteoporosismice keep the body weight in a normal growth level.2. Low and medium intensity exercise training can make the senile osteoporosismice increase BMD in a certain extent, and the effect of medium-intensityexercise training slow down declines of BMD is better than low-mediumintensity.3. Exercise training can make a certain improvement effect on part of the bonebiomechanical performance indicators of senile osteoporosis mice, andmedium-intensity exercise training effects more widely.4. High-intensity exercise training induced bone mineral density and part of thebone biomechanical performance indicators of femur osteoporosis of mousedecreased significantly, and shows no or negative impact.