date: 12/01/1985
author: Whedon GD.
publication: J Nutr Sci Vitaminol (Tokyo). 1985 Dec;31 Suppl:S41-4.
pubmed_ID: 3915756
Outside_URL: http://www.ncbi.nlm.nih.gov/pubmed/3915756
Many studies and observations have shown the bone-losing effects of physical inactivity of various forms. Contrariwise, less precise studies and observations have supported the reasonable premise that mechanical loading of the skeleton via physical activity shifts the balance of bone remodeling in favor of bone formation, and appears to do so at all ages. Some interesting starts have been made in research to discover the mechanisms of the action on bone of mechanical loading, but many pathways remain to be explored. Besides the mechanical forces, we need to know more about the interrelations of muscle function, probably mediated through muscle-tendon pull on periosteum, and more about other likely influences, notably changes in circulation to bones. The practical significance relative to calcium metabolism and aging of what has been learned thus far on the effects of activity, is that prolonged inactivity, either in a chair or in bed, is to be avoided, because of its deleterious effects, and that reasonably energetic gravitational exercise, such as walking or possibly jogging, promotes maintenance of bone health.
Category: Research and Articles
Cardiovascular responses to upright and supine exercise in humans after 6 weeks of head-down tilt (-6 degrees)
date: 11/01/2000
author: Sundblad P, Spaak J, Linnarsson D.
publication: Eur J Appl Physiol. 2000 Nov;83(4 -5):303-9.
pubmed_ID: 11138568
Seven healthy men performed steady-state dynamic leg exercise at 50 W in supine and upright postures, before (control) and repeatedly after 42 days of strict head-down tilt (HDT) (-6 degrees) bedrest. Steady-state heart rate (fc), mean arterial blood pressure, cardiac output (Qc), and stroke volume (SV) were recorded. The following data changed significantly from control values. The fc was elevated in both postures at least until 12 days, but not at 32 days after bedrest. Immediately after HDT, SV and Qc were decreased by 25 (SEM 3)% and 19 (SEM 3)% in supine, and by 33 (SEM 5)% and 20 (SEM 3)% in upright postures, respectively. Within 2 days there was a partial recovery of SV in the upright but not in the supine posture. The SV and Qc during supine exercise remained significantly decreased for at least a month. Submaximal oxygen uptake did not change after HDT. We concluded that the cardiovascular response to exercise after prolonged bedrest was impaired for so long that it suggested that structural cardiac changes had developed during the HDT period.
Effects of four weeks of absolute bed rest on circulatory functions in man.
date: 12/01/1964
author: Miller PB, Johnson RL, Lamb Le.
publication: Aerosp Med. 1964 Dec;35:1194-200.
pubmed_ID: 14230666
Femoral loads during passive, active, and active-resistive stance after spinal cord injury: a mathematical model.
date: 03/19/2004
author: Frey Law LA, Shields RK.
publication: Clin Biomech (Bristol, Avon). 2004 Mar;19(3):313-21.
pubmed_ID: 15003348
OBJECTIVE: The purpose of this study was to estimate the loading environment for the distal femur during a novel standing exercise paradigm for people with spinal cord injury. DESIGN: A mathematical model based on experimentally derived parameters. BACKGROUND: Musculoskeletal deterioration is common after spinal cord injury, often resulting in osteoporotic bone and increased risk of lower extremity fracture. Potential mechanical treatments have yet to be shown to be efficacious; however, no previous attempts have been made to quantify the lower extremity loading during passive, active, and active-resistive stance. METHODS: A static, 2-D model was developed to estimate the external forces; the activated quadriceps forces; and the overall bone compression and shear forces in the distal femur during passive (total support of frame), active (quadriceps activated minimally), and active-resistive (quadriceps activated against a resistance) stance. RESULTS: Passive, active, and active-resistive stance resulted in maximal distal femur compression estimates of approximately 45%, approximately 75%, and approximately 240% of body weight, respectively. Quadriceps force estimates peaked at 190% of body weight with active-resistive stance. The distal femur shear force estimates never exceeded 24% of body weight with any form of stance. CONCLUSIONS: These results support our hypothesis that active-resistive stance induces the highest lower extremity loads of the three stance paradigms, while keeping shear to a minimum. RELEVANCE: This model allows clinicians to better understand the lower extremity forces resulting from passive, active, and active-resistive stance in individuals with spinal cord injury.
Bone measurements by peripheral quantitative computed tomography (pQCT) in children with cerebral palsy
date: 12/01/2005
author: Binkley T, Johnson J, Vogel L, Kecskemethy H, Henderson R, Specker B.
publication: J Pediatr. 2005 Dec;147(6):791-6.
pubmed_ID: 16356433
OBJECTIVE: To use peripheral quantitative computed tomography (pQCT) to determine bone measurements in patients with cerebral palsy (CP) age 3 to 20 years and compare them with control subjects. STUDY DESIGN: A total of 13 (5 male) patients with CP, along with 2 sex- and age-matched controls for each, were included in a mixed-model analysis with matched pairs as random effects for pQCT bone measurements of the 20% distal tibia. RESULTS: Tibia length was similar in the CP and control groups (P = .57). Weight was marginally higher in the control group (P = .06). Cortical bone mineral content (BMC), area, thickness, polar strength-strain index (pSSI), and periosteal and endosteal circumferences were greater in the control group (P < .05 for all). Relationships between bone measurements and weight showed that cortical BMC, area, periosteal circumference, and pSSI were greater at higher weights in the control group (group-by-weight interaction, P < .05 for all). Cortical thickness was greater in the control group and was correlated with weight. Cortical volumetric bone mineral density (vBMD) was greater with higher weights in the CP group (group-by-weight interaction, P = .03). CONCLUSIONS: Bone strength, as indicated by pSSI, is compromised in children with CP due to smaller and thinner bones, not due to lower cortical bone density.
Longitudinal changes in bone density in children and adolescents with moderate to severe cerebral palsy.
date: 06/01/2005
author: Henderson RC, Kairalla JA, Barrington JW, Abbas A, Stevenson RD.
publication: J Pediatr. 2005 Jun;146(6):769-75
pubmed_ID: 15973316
OBJECTIVE: To assess the natural history of “growth” in bone mineral density (BMD) in children and adolescents with moderate to severe cerebral palsy (CP). STUDY DESIGN: A prospective, longitudinal, observational study of BMD in 69 subjects with moderate to severe spastic CP ages 2.0 to 17.7 years. Fifty-five subjects were observed for more than 2 years and 40 subjects for more than 3 years. Each evaluation also included assessments of growth, nutritional status, Tanner stage, general health, and various clinical features of CP. RESULTS: Lower BMD z-scores at the initial evaluation were associated with greater severity of CP as judged by gross motor function and feeding difficulty, and with poorer growth and nutrition as judged by weight z-scores. BMD increased an average of 2% to 5%/y in the distal femur and lumbar spine, but ranged widely from +42%/y to -31%. In spite of increases in BMD, distal femur BMD z-scores decrease with age in this population. CONCLUSIONS: Children with severe CP develop over the course of their lives clinically significant osteopenia. Unlike elderly adults, this is not primarily from true losses in bone mineral, but from a rate of growth in bone mineral that is diminished relative to healthy children. The efficacy of interventions to increase BMD can truly be assessed only with a clear understanding of the expected changes in BMD without intervention.
Bone mineral density in children with cerebral palsy.
date: 04/01/2001
author: Tasdemir HA, Buyukavci M, Akcay F, Polat P, Yildiran A, Karakelleoglu C.
publication: Pediatr Int. 2001 Apr;43(2):157-60.
pubmed_ID: 11285068
BACKGROUND: The purpose of the present study was to evaluate the severity of and factors related to osteopenia in children with cerebral palsy (CP). METHODS: Bone mineral density (BMD), calcium (Ca), phosphate (P), alkaline phosphatase (ALP), creatinine, parathyroid hormone (PTH) and 25-hydroxy vitamin D3 (25OHD3) concentrations were determined in 24 children with CP (15 ambulant, nine non-ambulant), aged between 10 months and 12 years (mean (+/-SD) 4.1+/-2.9 years). These vaules were compared with data obtained from a control group. RESULTS: Adjusted mean BMD values were lower in the patient group than in controls (P<0.05). However, there was no difference between BMD values of ambulant and non-ambulant patients. The Ca and P levels of the patient group were significantly higher than those of controls (P<0.05). CONCLUSIONS: The present study showed that BMD was decreased in all children with CP, but to a greater extent in non-ambulant children with CP, and immobilization is the major effective factor on bone mineralization.
Changes of tibia bone properties after spinal cord injury: effects of early intervention.
date: 02/01/1999
author: De Bruin ED, Frey-Rindova P, Herzog RE, Dietz V, Dambacher MA, Stussi E.
publication: Arch Physical Medicine Rehabilitation. 1999 Feb;80(2):214-20.
pubmed_ID: 10025500
OBJECTIVE: To evaluate the effectiveness of an early intervention program for attenuating bone mineral density loss after acute spinal cord injury (SCI) and to estimate the usefulness of a multimodality approach in diagnosing osteoporosis in SCI. DESIGN: A single-case, experimental, multiple-baseline design. SETTING: An SCI center in a university hospital. METHODS: Early loading intervention with weight-bearing by standing and treadmill walking. PATIENTS: Nineteen patients with acute SCI. OUTCOME MEASURES: (1) Bone density by peripheral computed tomography and (2) flexural wave propagation velocity with a biomechanical testing method. RESULTS: Analysis of the bone density data revealed a marked decrease of trabecular bone in the nonintervention subjects, whereas early mobilized subjects showed no or insignificant loss of trabecular bone. A significant change was observed in 3 of 10 subjects for maximal and minimal area moment of inertia. Measurements in 19 subjects 5 weeks postinjury revealed a significant correlation between the calculated bending stiffness of the tibia and the maximal and minimal area moment of inertia, respectively. CONCLUSION: A controlled, single-case, experimental design can contribute to an efficient tracing of the natural history of bone mineral density and can provide relevant information concerning the efficacy of early loading intervention in SCI. The combination of bone density and structural analysis could, in the long term, provide improved fracture risk prediction in patients with SCI and a refined understanding of the bone remodeling processes during initial immobilization after injury.
Mobility status and bone density in cerebral palsy.
date: 08/01/1996
author: Wilmshurst S, Ward K, Adams JE, Langton CM, Mughal MZ.
publication: Arch Dis Child. 1996 Aug;75(2):164-5.
pubmed_ID: 8869203
The spinal bone mineral density (SBMD) and calcaneal broadband ultrasound attenuation (BUA) was measured in 27 children with cerebral palsy. They were categorised into four mobility groups: mobile with an abnormal gait, mobile with assistance, non-mobile but weight bearing, non-mobile or weight bearing. Mean SD scores for BUA and SBMD differed among mobility groups (analysis of variance, p < 0.001 and p = 0.078, respectively).
Effect of prolonged bed rest on bone mineral.
date: 12/19/1970
author: Donaldson CL, Hulley SB, Vogel JM, Hattner RS, Bayers JH, McMillan DE.
publication: Metabolism. 1970 Dec; 19(12): 1071-84
pubmed_ID: 4321644
Outside_URL: http://www.ncbi.nlm.nih.gov/pubmed/4321644
Bone mineral is lost during immobilization. This disuse osteopenia occurs locally in patients with fracture or hemiplegia and is generalized in quadriplegia.