This study investigated how different treadmill running periods effected bone mechanical strength in ovariectomized mice. Eighty female ICR mice aged 12-weeks-old were used. All mice were divided into 8 groups (n=10) randomly, and had either a sham-operation (n=10) or an ovariectomy (n=70). The SHAM group and one OVX group (NR) were used as non-running control groups, with the remainder comprising the treadmill running groups : the LA (8 m/min), MA (16 m/min), and HA (24 m/min) groups which ran for 12 weeks, and the LB (8 m/min), MB (16 m/min), HB (24 m/min) groups which ran for 6 weeks for 25 min on 5 days/week. After this experiment, maximum loads for the femur and tibia were measured by three-pointed bending test, and the bone mechanical strength of the bones was calculated. Also, the dry bone weight and ash content of the bones were measured. Maximum femur and tibia load and bone mechanical strength were affected by running speed and term significantly. Maximum load and bone mechanical strength of tibia were shown as an interaction. Bone mechanical strength in all running groups was higher than that in the NR group, significantly. This study suggested that treadmill running prevented a reduction of bone mechanical strength, and that treadmill running was most effective in the LA and MA groups (running at low and medium speed and for a long period).

Effects of running speed and duration on a treadmill on bone properties were investigated in ovariectomized (OVX) mice. Sixty female ICR mice, twelve-weeks-old, were used in this study. They were divided into six groups of 10 mice each : either the SHAM, OVX, OVX+running groups (AS, AL, BS, BL), randomly. Running groups ran on the treadmill at 8 (A) or 16 (B) m/min, for 25 (S) or 50 (L) min, 5 days/week, for 10 weeks, respectively. After this, both femur and tibia bones were excised from the hind limb, and removed off surrounding tissues. Thereafter, bone mechanical strength (3 point bending test), dry bone weight and also ash content of the bones were determined. Bone mechanical strength and ash content of the femur and tibia in AL, BS, and BL mice were significantly higher than those in OVX mice. Running speed had effects on the bone mechanical strength and ash content of both bones significantly. Group BL showed the maximum values in bone properties among the running groups. This study suggested that a combination of running speed and duration could affect bone properties more significantly than the amount of exercise alone.

This study investigated the effects of electrical stimulus on bone properties in rats with sciatic denervation. Forty-eight Wistar rats aged 8 week-old were used and divided into 4 groups, randomly. One group was sham-operated (SHAM) as a control, and the sciatic nerves of the lateral hind limbs were cut in the remaining 3 groups (DN). Two groups of DN rats received electrical stimulus at both hind limbs to induce planter flexion for 15 min, 2 sets/day, 5 days/week, at 15 or 60 Hz. The rats in each group were sacrificed at 1, 2, 3 and 4 weeks after the operation. All tibias were measured by three-pointed bending test, and bone mechanical strength was calculated. Also, the dry bone weight and ash content of the bones were measured. A reduction of all bone properties in DN was shown from a week after operation onwards and that in DN+15 Hz from two weeks after operation onwards. Bone properties in DN+60 Hz were decreased in order of maximum load, ash content, mechanical strength, and dry bone weight from two weeks after operation onwards. These results suggest that electrical stimulus can delay the progression of bone atrophy, and that high frequency stimulation (60 Hz) is more effective than low frequency stimulation (15 Hz) in this regard.

OBJECTIVES: This study aimed to investigate differences in physical function by bone mass category as assessed by speed of sound, and the association between bone mass and physical function in Japanese elderly women. METHODS: Participants (≥65 years, n = 954) were divided into the osteoporosis, osteopenia, and normal groups based on speed of sound values, and physical function parameters were compared among groups. In addition, the predictive ability of physical function for low bone mass was determined by area under the curve analysis. Data were collected in 4 cities in Nara, Japan, in 2007 or 2008. RESULTS: All physical functions were significantly lower in the osteoporotic group than in the normal group. Lower bone mass was associated with poor muscle strength and physical function after adjusting for age, height and weight. In addition, one-leg standing time and 10-m gait time were predictive of low bone mass (osteopenia and osteoporosis levels, respectively). Elderly women with low physical function, especially those with a short one-leg standing time, should be suspected of having decreased bone mass. CONCLUSIONS: Measurements of physical function can effectively identify elderly women with low bone mass at an early stage without the need for bone mass measurements. In particular, one-leg standing time and 10-m gait time were good predictors of low bone mass, and is easy to measure, low-cost, and can be self-measured. These findings will be helpful in the prevention and treatment of osteoporosis.
Aged* ; Asian Continental Ancestry Group ; Bone Diseases, Metabolic ; Female ; Gait ; Humans ; Japan ; Muscle Strength ; Osteoporosis ; Ultrasonography*

OBJECTIVES: To examine the effects of whole body vibration (WBV) on bone properties in growing rats, and to explore the optimal conditions for enhancing bone properties. METHODS: Thirty-six 4-week-old male rats were divided into 1 control and 5 experimental groups. Each experimental group underwent WBV at 15, 30, 45, 60, and 90 Hz (0.5 g, 15 min/d, 5 d/wk) for 8 weeks.We measured bone size, muscle weight and bone mechanical strength of the right tibia. Trabecular bone mass and trabecular bone microstructure (TBMS) of the left tibia were analyzed by micro-computed tomography. Serum levels of bone formation/resorption markers were also measured. RESULTS: WBV at 45 Hz and 60 Hz tended to enhance trabecular bone mass and TBMS parameters. However, there was no difference in maximum load of tibias among all groups. Serum levels of bone resorption marker were significantly higher in the 45-Hz WBV group than in the control group. CONCLUSIONS: WBV at 45–60 Hz may offer a potent modality for increasing bone mass during the period of rapid growth. Further studies are needed to explore the optimal WBV conditions for increasing peak bone mass and TBMS parameters. WBV modality may be a potent strategy for primary prevention against osteoporosis.
Animals ; Bone Resorption ; Humans ; Male ; Osteoporosis ; Primary Prevention ; Rats ; Tibia ; Vibration

OBJECTIVES: Type 2 diabetes mellitus (T2DM) increases fracture risk despite normal to high levels of bone mineral density. Bone quality is known to affect bone fragility in T2DM. The aim of this study was to clarify the trabecular bone microstructure and cortical bone geometry of the femur in T2DM model rats. METHODS: Five-week-old Otsuka Long-Evans Tokushima Fatty (OLETF; n = 5) and Long-Evans Tokushima Otsuka (LETO; n = 5) rats were used. At the age of 18 months, femurs were scanned with micro-computed tomography, and trabecular bone microstructure and cortical bone geometry were analyzed. RESULTS: Trabecular bone microstructure and cortical bone geometry deteriorated in the femur in OLETF rats. Compared with in LETO rats, in OLETF rats, bone volume fraction, trabecular number and connectivity density decreased, and trabecular space significantly increased. Moreover, in OLETF rats, cortical bone volume and section area decreased, and medullary volume significantly increased. CONCLUSIONS: Long-term T2DM leaded to deterioration in trabecular and cortical bone structure. Therefore, OLETF rats may serve as a useful animal model for investigating the relationship between T2DM and bone quality.
Animals ; Bone Density ; Diabetes Mellitus, Type 2 ; Femur ; Models, Animal ; Rats* ; Rats, Inbred OLETF