Mechanical, morphological and biochemical adaptations of bone and muscle to hindlimb suspension and exercise

Shaw, Stephen R.; Zernicke, Ronald F.; Vailas, A. C.; DeLuna, D.; Thomason, Donald B.; Baldwin, Kenneth M.

doi:10.1016/0021-9290(87)90289-2

Cited by 79 publications

(44 citation statements)

References 52 publications

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“…The mechanical tests on the proximal femur and cortical bone samples indicated that tail suspension for 28 days significantly weakened bone, in agreement with previous studies (3,34,36,37). These results support the idea that tail suspension is a good model for skeletal disuse atrophy.…”

Section: Discussionsupporting

confidence: 81%

“…When mechanical tests are performed on an entire bone segment, they reflect the bone structural properties; when standardized samples are used, the resulting information reflects the characteristics of bone as a tissue (34,35). The mechanical tests on the proximal femur and cortical bone samples indicated that tail suspension for 28 days significantly weakened bone, in agreement with previous studies (3,34,36,37).…”

Section: Discussionsupporting

confidence: 76%

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Biomechanics and structural adaptations of the rat femur after hindlimb suspension and treadmill running

Shimano¹,

Volpon²

2009

Braz J Med Biol Res

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We microscopically and mechanically evaluated the femurs of rats subjected to hindlimb unloading (tail suspension) followed by treadmill training. Female Wistar rats were randomly divided into five groups containing 12-14 rats: control I (118 days old), control II (139 days old), suspended (tail suspension for 28 days), suspended-released (released for 21 days after 28 days of suspension), and suspended-trained (trained for 21 days after 28 days of suspension). We measured bone resistance by bending-compression mechanical tests of the entire proximal half of the femur and three-point bending tests of diaphyseal cortical bone. We determined bone microstructure by tetracycline labeling of trabecular and cortical bone. We found that tail suspension weakened bone (ultimate load = 86.3 ± 13.5 N, tenacity modulus = 0.027 ± 0.011 MPa·m vs ultimate load = 101.5 ± 10.5 N, tenacity modulus = 0.019 ± 0.006 MPa·m in control I animals). The tenacity modulus for suspended and released animals was 0.023 ± 0.010 MPa·m vs 0.046 ± 0.018 MPa·m for trained animals and 0.035 ± 0.010 MPa·m for control animals. These data indicate that normal activity and training resulted in recovered bone resistance, but suspended-released rats presented femoral head flattening and earlier closure of the growth plate. Microscopically, we found that suspension inhibited new bone subperiosteal and endosteal formation. The bone disuse atrophy secondary to hypoactivity in rats can be reversed by an early regime of exercising, which is more advantageous than ordinary cage activities alone.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionsupporting

confidence: 76%

Biomechanics and structural adaptations of the rat femur after hindlimb suspension and treadmill running

Shimano¹,

Volpon²

2009

Braz J Med Biol Res

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“…For example, in immobilized turkey radii, more than half (+58%) of the disuse-induced increase in porosity occurred within the ventral/caudal quadrant of the cortex [35]. Similarly, hindlimb suspension decreased the cortical thickness of the anterior quadrant (but not other quadrants) in the femur of hindlimb suspended rats which lowered whole bone strength [45]. In contrast, there were no significant differences in porosity or cortical thickness between anatomical quadrants for hibernating or active grizzly bears, suggesting that hibernation did not cause localized bone structural changes in a focused region of the femoral cortex.…”

Section: Discussionmentioning

confidence: 99%

Decreased bone turnover with balanced resorption and formation prevent cortical bone loss during disuse (hibernation) in grizzly bears (Ursus arctos horribilis)

McGee

Maki

Johnson

et al. 2008

Bone

102

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Disuse uncouples bone formation from resorption, leading to increased porosity, decreased bone geometrical properties, and decreased bone mineral content which compromises bone mechanical properties and increases fracture risk. However, black bear bone properties are not adversely affected by aging despite annual periods of disuse (i.e., hibernation), which suggests that bears either prevent bone loss during disuse or lose bone and subsequently recover it at a faster rate than other animals. Here we show decreased cortical bone turnover during hibernation with balanced formation and resorption in grizzly bear femurs. Hibernating grizzly bear femurs were less porous and more mineralized, and did not demonstrate any changes in cortical bone geometry or whole bone mechanical properties compared to active grizzly bear femurs. The activation frequency of intracortical remodeling was 75% lower during hibernation than during periods of physical activity, but the normalized mineral apposition rate was unchanged. These data indicate bone turnover decreases during hibernation, but osteons continue to refill at normal rates. There were no changes in regional variation of porosity, geometry, or remodeling indices in femurs from hibernating bears, indicating that hibernation did not preferentially affect one region of the cortex. Thus, grizzly bears prevent bone loss during disuse by decreasing bone turnover and maintaining balanced formation and resorption, which preserves bone structure and strength. These results support the idea that bears possess a biological mechanism to prevent disuse osteoporosis.

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“…Without adequate control for the effects of body size, skeletal traits may appear to vary significantly among groups that experience different exercise regimens when the groups differ primarily in body size alone. Some studies on the effect of exercise or loading on bone do include body mass in statistical analyses (e.g., Gordon et al, 1989;Kannus et al, 1995;Järvinen et al, 2003;Binkley and Specker, 2004), but many do not, even when body mass differs significantly between control and treatment groups (e.g., Shaw et al, 1987;Niehoff et al, 2004;Wu et al, 2004).…”

Section: Morphometrics -Importance Of Body Massmentioning

confidence: 99%

The relative importance of genetics and phenotypic plasticity in dictating bone morphology and mechanics in aged mice: Evidence from an artificial selection experiment

Middleton

Shubin

Moore

et al. 2008

Zoology

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Both genetic and environmental factors are known to influence the structure of bone, contributing to its mechanical behavior during, and adaptive response to, loading. We introduce a novel approach to simultaneously address the genetically mediated, exercise-related effects on bone morphometrics and strength, using mice that had been selectively bred for high levels of voluntary wheel running (16 generations). Female mice from high-running and control lines were either allowed (n = 12, 12; respectively) or denied (n = 11, 12; respectively) access to wheels for 20 months. Femoral shaft, neck, and head were measured with calipers and via micro-computed tomography. Fracture characteristics of the femoral head were assessed in cantilever bending. After adjusting for variation in body mass by two-way analysis of covariance, distal width of the femur increased as a result of selective breeding, and mediolateral femoral diameter was reduced by wheel access. Cross-sectional area of the femoral mid-shaft showed a significant linetype × activity effect, increasing with wheel access in high-running lines but decreasing in control lines. Body mass was significantly positively correlated with many of the morphometric traits studied. Fracture load of the femoral neck was strongly positively predicted by morphometric traits of the femoral neck (r 2 > 0.30), but no significant effects of selective breeding or wheel access were found. The significant correlations of body mass with femoral morphometric traits underscore the importance of controlling for body size when analyzing the response of bone size and shape to experimental treatments. After controlling for body mass, measures of the femoral neck remain significant predictors of femoral neck strength.

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Mechanical, morphological and biochemical adaptations of bone and muscle to hindlimb suspension and exercise

Cited by 79 publications

References 52 publications

Biomechanics and structural adaptations of the rat femur after hindlimb suspension and treadmill running

Biomechanics and structural adaptations of the rat femur after hindlimb suspension and treadmill running

Decreased bone turnover with balanced resorption and formation prevent cortical bone loss during disuse (hibernation) in grizzly bears (Ursus arctos horribilis)

The relative importance of genetics and phenotypic plasticity in dictating bone morphology and mechanics in aged mice: Evidence from an artificial selection experiment

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