How many days per week should rats undergo running exercise to increase BMD?

Abstract

The aim of the present study was to examine the effect of different frequencies of running exercise on increasing bone mineral density (BMD) and improving bone histomorphology at various sites of the skeleton (tibia, femur, and second lumbar vertebra) in young rats. Twenty-five female Wistar rats, 8 weeks old, were divided into five groups, of 5 animals each according to running load: control group, no running (A group); running load (RL), 4 days per week (d/w; B group); RL, 5 d/w (C group); RL, 6 d/w (D group); and RL, 7 d/w (E group). Rats ran on a treadmill at a speed of 15 m/min for 30 min per day over an 8-week period. The results indicated that the BMD of the tibia in the B, C, D, and E groups and that of the femur in the B and E groups increased significantly over that of the A group. However, the cortical BMD and trabecular BMD of the second lumbar vertebra did not change. In regard to bone histomorphometry of the tibia, a parameter of bone resorption (eroded surface/bone surface) was significantly lower in the B and D groups than in the A group. There were no differences in the parameters of bone formation. Tartaric acid-resistant acid phosphatase (TRACP) values were significantly lower in the B and C groups than in the A group. There were significant increases in body weight in the B group and in muscle weight in the C group. From the data obtained in this study, it was concluded that increases in BMD were obtained by a moderate running load at frequencies of 4 and 5 days per week.

Running Exercise for Short Duration Increases Bone Mineral Density of Loaded Long Bones in Young Growing Rats

“…The running load was initiated when the rats were 8 weeks old. The running conditions were determined according to our previous publications (Hagihara et al 2000(Hagihara et al , 2005. All rats ran at a treadmill speed of 15 m/min, a speed at which they ran voluntarily and did not drop out.…”

“…Using young growing rats, we previously verified the effects of moderate exercise in the form of running on a treadmill at a speed of 15 m/min for 30 min per day, over an 8-week period, on BMD of the long bones. We determined that the appropriate exercise frequency to increase BMD of the long bones was 4 to 5 days per week (Hagihara et al 2005). However, the optimal combination of exercise frequency and duration to maximize BMD has not been established.…”

The role of physical activity in early adulthood and middle-age on bone health after menopause in epidemiological population from Silesia Osteo Active Study

“…27,28 The lack of consistent opinion is caused by different exercise protocols and participants' cooperation and therefore needs further investigation.…”

Increased intrinsic stiffness and mineralization in femurs of adult rats after high intensity treadmill running training

“…The effect of treadmill exercise on bone mass in rodents has been previously studied [8][9][10][11][12]. The time and the degree of the endurance treadmill running training were not uniform in the different studies, although most of them revealed that this type of exercise has effects on bone density, size and shape, resulting in substantial improvements in mechanical strength.…”

“…Increased Young's modulus and higher concentration of Ca in femurs of trained rats were also described [9]. In general, increases in bone mineral density (BMD) can be obtained by a moderate running load (15 m/min for 30 min) at frequencies of 4 and 5 days per week [11]. It has also been reported that the effect of exercise on bone at an older age is different from that at other ages [14].…”