Effects of resistance exercise training on mass, strength, and turnover of bone in growing rats

Abstract

To determine the effects of resistance exercise on mass, strength and local turnover of bone, 50 Sprague Dawley rats, 8 weeks of age, were assigned to five groups: a baseline control and two groups of sedentary and exercising rats. The trunk of the rats was kept upright during electrically stimulated jumping exercise for 1 h every other day. In 4 weeks, the trabecular mineralizing surface per bone surface (MS/BS), bone formation rate per bone surface (BFR/BS) and the compression load of the lumbar body increased and the number of osteoclasts decreased, but bone mineral density (BMD) and structure did not increase. In the mid femur, the cross-sectional area, the cortical bone area, the moment of inertia, the periosteal MS/BS, BFR/BS and the bending load increased in the exercise group. In 8 weeks, the increases in BMD, structure and load values were significant in both the lumbar and mid femur. At both 4 and 8 weeks, the MS/BS for the endocortical surface of mid femur were not increased and mineral apposition rate (MAR) remained reduced. These results show that jumping exercise increases the mass and strength of the lumbar vertebrae and mid femur by stimulating bone formation and accelerates cortical drift by both increasing periosteal bone formation and reducing the endocortical MAR.

Effect of Different Intake Levels of Dietary Protein and Physical Exercise on Bone Mineral Density and Bone Strength in Growing Male Rats

“…Interestingly, the harmful effect of physical exercise was observed on the femoral breaking energy in the high protein group, while not shown on the BMD. Although voluntary wheel running (17), jumping (18), treadmill running (19) have demonstrated the benefi cial effects of increased load on bone mass or mechanical properties of the femur, tibia, and humerus, the effects of physical exercise were not similar among the different levels of protein intake in our study. Seventy percent of bone strength depends on its density and 30% depends on its quality (20).…”

High-impact exercise strengthens bone in osteopenic ovariectomized rats with the same outcome as Sham rats

“…Tamaki et al (30) found running to significantly increase BMD of the femoral diaphysis in OVX rats. In addition, Notomi et al (25) found resistance exercise to significantly increase BMD of the femoral diaphysis in male rats. However, the same effect was not observed with running in male rats.…”

“…It can be inferred that microarchitectural changes occurred alongside the observed increase in BMD of cancellous bone in the present experiment. On the other hand, varying effects of exercise on the diaphysis have been observed by a number of researchers (25,26,30). Tamaki et al (30) found running to significantly increase BMD of the femoral diaphysis in OVX rats.…”

“…Human studies investigating osteogenic responses to exercise have examined many kinds of training programs, including running and walking (8,12,19), resistance training (18,19), aerobic exercise (8,13,20), and high-impact or jump exercise (5,7,10). Most animal studies have investigated treadmill running (1,2,16,(27)(28)(29)37), although other types of training programs have also been examined (11,25,26). Among all types of exercise programs, high-impact exercise is thought to be greatly beneficial to bone.…”

Effects of Voluntary Resistance Exercise and High-protein Snack on Bone Mass, Composition, and Strength in Rats Given Glucocorticoid Injections

“…7) Animal exercise models are used to examine the preventive or recovery eŠect of exercise on bone mass and strength as endpoints of an experiment. Animal studies using voluntary wheel running, 11) jumping, 12) treadmill running, 13) or voluntary climbing 9,14,15) have demonstrated the beneˆcial eŠect of increased load on bone mass and mechanical properties. Voluntary tower climbing is a light resistance exercise that creates little stress and strain and has been used in several studies.…”