Abstract
Three-dimensional femoral trabecular architecture was investigated in tail-suspended young growing rats and the effects of jump exercise during the period of tail-suspension were also examined. Eight-week-old male Wistar rats (n = 24) were randomly assigned to three body weight-matched groups: a tail suspended group (SUS, n = 8); a sedentary control group (CON, n = 8) and rats primed with jump exercise during the period of tail suspension (JUM, n = 8). The jump exercise protocol consisted of 30 jumps/day, five days/week with a 40 cm jump height. After 3 weeks of jump exercise, bone mineral density (BMD) of the entire right femur was measured using dual energy X-ray absorptiometry. Three-dimensional trabecular bone architecture at the distal femoral metaphysis was evaluated using microcomputed tomography (micro-CT). Tail suspension caused a decrease in femoral BMD (−5%, p < 0.001) and trabecular bone architectural deterioration. Deterioration in the trabecular network during hindlimb unloading was mostly attributed to the reduction of trabecular number (−32%, p < 0.001) in the distal femoral metaphysis. Jump exercise during the tail suspension period increased trabecular thickness (14%, p < 0.001) and the reduction of trabecular number was suppressed. The present data indicate that jump exercise applied during hindlimb unloading could be able to inhibit bone loss and trabecular bone architectural deterioration caused by tail suspension.
Highlights
Long-duration exposure to a microgravity environment has been shown to have detrimental effects on the human skeletal system
We have previously reported that suspension-induced trabecular deterioration persists after remobilization and that jump exercise during the remobilization period could restore the integrity of trabecular architecture in the femur of young growing rats (Ju et al 2008)
After one week of acclimation to the diet and new environment, rats were randomly assigned into three groups (n = 8 each): tail-suspended group (SUS); sedentary control group reared in the breeding cage (CON); and rats primed with jump exercise during the period of tail suspension (JUM)
Summary
Long-duration exposure to a microgravity environment has been shown to have detrimental effects on the human skeletal system. No published animal studies have evaluated the effects of jump exercise on maintaining bone architecture during periods of tail suspension. Swift et al (2011) recently demonstrated that highintensity simulated resistance training completed every other day during a period of disuse can prevent the loss of cancellous bone mass and material properties. Their results could differ from that of the physiological (exercise) model in trabecular bone architecture because these studies used artificial mechanical loading models under anesthesia. The aim of the current study was to investigate the effectiveness of jump exercise on preserving bone mass and architectural deterioration of trabecular bone during hindlimb unloading
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