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
Changes in physical strain and physical capacity in men with spinal cord injuries.
date: 05/01/1996
author: Janssen TW, van Oers CA, Rozendaal EP, Willemsen EM, Hollander AP, van der Woude LH.
publication: Med Sci Sports Exerc. 1996 May;28(5):551-9.
pubmed_ID: 9148083
To determine longitudinal changes in physical capacity and physical strain during activities of daily living (ADL), 37 men with spinal cord injuries (C4/5-L5) performed an exercise test and various ADL on two occasions (T1 and T2; interval 34.5 +/- 1.5 months). Parameters of physical capacity were aerobic power (VO(2peak)) and maximal power output (PO(max)). Physical strain was estimated by the heart rate response relative to the heart rate reserve. VO(2peak) at T2 (1.75 +/- 0.55 1*min(1)) did not significantly differ from that at T1 (1.67 + 0.47 1*min(-1)). Absolute PO max improved (P < 0.05) from 64.9 +/- 25.9 (T1) to 71.7 +/- 27.2 W (T2), whereas relative PO(max) did not change. Activity level, time since injury, change in body mass, and occurrence of rehospitalization were the most important predictors of changes in physical capacity. Changes in relative VO(2peak) were related (P < 0.05) to changes in strain during transfers to the shower wheelchair (r = -0.39) and shower seat (r = -0.46), and during the curb ascent (r = -0.47). In conclusion, the hypothesized decline in physical capacity did not occur over the 3-yr period. Maintenance of physical capacity, which may in part be achieved through sport participation and improved medical care, together with avoidance of excessive body mass, may be useful to prevent high levels of strain during ADL.
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.
A motorized dynamic stander.
date: 03/01/2002
author: Gudjonsdottir B, Mercer VS.
publication: Pediatr Phys Ther. 2002 Spring;14(1):49-51.
pubmed_ID: 17053681
PURPOSE: The purpose of this clinical suggestion is to describe a new type of a stander, a dynamic stander. KEY POINTS: The dynamic stander may give children with severe cerebral palsy an opportunity for movement in lower extremities and trunk while they are standing. It may increase their tolerance for standing in a stander for a considerable period of time. In addition, the potential for increased bone mineral density might be greater with a dynamic stander than a conventional stander. The design, development, and initial clinical use of the new type of stander is described. SUMMARY: Some minor problems related to the design of the dynamic stander were noted. Design changes to correct these problems could be easily implemented before the introduction of the stander for more widespread clinical use.
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
The effect of a weight-bearing physical activity program on bone mineral content and estimated volumetric density in children with spastic cerebral palsy.
date: 07/01/1999
author: Chad KE, Bailey DA, McKay HA, Zello GA, Snyder RE.
publication: J Pediatr 1999 Jul;135(1):115-7.
pubmed_ID: 10393617
After an 8-month physical activity intervention in children with cerebral palsy, increases in femoral neck bone mineral content (BMC) (9.6%), volumetric bone mineral density (v BMD) (5.6%), and total proximal femur BMC (11.5%) were observed in the intervention group (n = 9) compared with control subjects (n = 9; femoral neck BMC, -5. 8%; v BMD, -6.3%; total proximal femur BMC, 3.5%).
Publication Types:
? Clinical Trial
? Randomized Controlled Trial
Low magnitude mechanical loading is osteogenic in children with disabling conditions.
date: 03/19/2004
author: Ward K, Alsop C, Caulton J, Rubin C, Adams J, Mughal Z.
publication: J Bone Miner Res. 2004 Mar;19(3):360-9. Epub 2004 Jan 27.
pubmed_ID: 15040823
The osteogenic potential of short durations of low-level mechanical stimuli was examined in children with disabling conditions. The mean change in tibia vTBMD was +6.3% in the intervention group compared with -11.9% in the control group. This pilot randomized controlled trial provides preliminary evidence that low-level mechanical stimuli represent a noninvasive, non-pharmacological treatment of low BMD in children with disabling conditions. INTRODUCTION: Recent animal studies have demonstrated the anabolic potential of low-magnitude, high-frequency mechanical stimuli to the trabecular bone of weight-bearing regions of the skeleton. The main aim of this prospective, double-blind, randomized placebo-controlled pilot trial (RCT) was to examine whether these signals could effectively increase tibial and spinal volumetric trabecular BMD (vTBMD; mg/ml) in children with disabling conditions. MATERIALS AND METHODS: Twenty pre-or postpubertal disabled, ambulant, children (14 males, 6 females; mean age, 9.1 +/- 4.3 years; range, 4-19 years) were randomized to standing on active (n = 10; 0.3g, 90 Hz) or placebo (n = 10) devices for 10 minutes/day, 5 days/week for 6 months. The primary outcomes of the trial were proximal tibial and spinal (L2) vTBMD (mg/ml), measured using 3-D QCT. Posthoc analyses were performed to determine whether the treatment had an effect on diaphyseal cortical bone and muscle parameters. RESULTS AND CONCLUSIONS: Compliance was 44% (4.4 minutes per day), as determined by mean time on treatment (567.9 minutes) compared with expected time on treatment over the 6 months (1300 minutes). After 6 months, the mean change in proximal tibial vTBMD in children who stood on active devices was 6.27 mg/ml (+6.3%); in children who stood on placebo devices, vTBMD decreased by -9.45 mg/ml (-11.9%). Thus, the net benefit of treatment was +15.72 mg/ml (17.7%; p = 0.0033). In the spine, the net benefit of treatment, compared with placebo, was +6.72 mg/ml, (p = 0.14). Diaphyseal bone and muscle parameters did not show a response to treatment. The results of this pilot RCT have shown for the first time that low-magnitude, high-frequency mechanical stimuli are anabolic to trabecular bone in children, possibly by providing a surrogate for suppressed muscular activity in the disabled. Over the course of a longer treatment period, harnessing bone’s sensitivity to these stimuli may provide a non-pharmacological treatment for bone fragility in children.
Pathological fractures in patients with cerebral palsy.
date: 10/01/1996
author: Brunner R, Doderlein L.
publication: J Pediatr Orthop B. 1996 Fall;5(4):232-8. Comment in: J Pediatr Orthop B. 1996 Fall;5(4):223-4.
pubmed_ID: 8897254
A retrospective study was made of 37 patients with 54 fractures that occurred without significant trauma. The morbidity and causes of these pathological fractures in patients with cerebral palsy were analyzed. The major causes for the fractures were long and fragile lever arms and stiffness in major joints, particularly the hips and knees. An additional factor was severe osteoporosis following a long period of postoperative immobilization. Seventy-four percent of the fractures occurred in the femoral shaft and supracondylar region. Stress fractures were rare (7%) and involved only the patella. Conservative treatment was sufficient in most cases but surgical fixation provided a good alternative for fractures of the femoral shaft. Intraarticular fractures with joint incongruity resulted in a decreased level of activity of the patient. Since osteoporosis is a major risk factor, patients with cerebral palsy should bear weight to prevent pathological fractures. Any stiffness of major joints and extended periods of immobilization should be avoided.
Static vs dynamic loads as an influence on bone remodeling.
date: 01/01/2004
author: Lanyon LE, Rubin CT.
publication: J Biomech. 1984;17(12):897-905.
pubmed_ID: 6520138
Remodeling activity in the avian ulna was assessed under conditions of disuse alone, disuse with a superimposed continuous compressive load, and disuse interrupted by a short daily period of intermittent loading. The ulnar preparation consisted of the 110mm section of the bone shaft between two submetaphyseal osteotomies. Each end of the preparation was transfixed by a stainless steel pin and the shaft either protected from normal functional loading with the pins joined by external fixators, loaded continuously in compression by joining the pins with springs, or loaded intermittently in compression for a single 100s period per day by engaging the pins in an Instron machine. Similar loads (525 N) were used in both static and dynamic cases. The strains engendered were determined by strain gauges, and at their maximum around the bone’s midshaft were -0.002. The intermittent load was applied at a frequency of 1 Hz as a ramped square wave, with a rate of change of strain during the ramp of 0.01 s-1. Peak strain at the midshaft of the ulna during wing flapping in the intact bone was recorded from bone bonded strain gauges in vivo as -0.0033 with a maximum rate of change of strain of 0.056 s-1. Examination of bone sections from the midpoint of the preparation after an 8 week period indicated that in both non-loaded and statically loaded bones there was an increase in both endosteal diameter and intra cortical porosity. These changes produced a decrease in cross sectional area which was similar in the two groups (-13%).(ABSTRACT TRUNCATED AT 250 WORDS)
Bone density and metabolism in children and adolescents with moderate to severe cerebral palsy.
date: 07/01/2002
author: Henderson RC, Lark RK, Gurka MJ, Worley G, Fung EB, Conaway M, Stallings VA, Stevenson RD.
publication: Pediatrics. 2002 Jul;110(1 Pt 1):e5.
pubmed_ID: 12093986
OBJECTIVES: Diminished bone density and a propensity to fracture with minimal trauma are common in children and adolescents with moderate to severe cerebral palsy (CP). The purpose of this study was to provide a detailed evaluation of bone mineral density (BMD) and metabolism in this population and to assess the relationship of these measures to multiple other clinical, growth, and nutrition variables. METHODS: The study group consisted of 117 subjects ages 2 to 19 years (mean: 9.7 years) with moderate to severe CP as defined by the Gross Motor Functional Classification scale. Population-based sampling was used to recruit 62 of the participants, which allows for estimations of prevalence. The remaining 55 subjects were a convenience sampling from both hospital- and school-based sources. The evaluation included measures of BMD, a detailed anthropometric assessment of growth and nutritional status, medical and surgical history, the Child Health Status Questionnaire, and multiple serum analyses. BMD was measured in the distal femur, a site specifically developed for use in this contracted population, and the lumbar spine. BMD measures were converted to age and gender normalized z scores based on our own previously published control series (n > 250). RESULTS: Osteopenia (BMD z score <-2.0) was found in the femur of 77% of the population-based cohort and in 97% of all study participants who were unable to stand and were older than 9 years. BMD was not as low in the lumbar spine (population-based cohort mean +/- standard error z score: -1.8 +/- 0.1) as in the distal femur (mean z score: -3.1 +/- 0.2). Fractures had occurred in 26% of the children who were older than 10 years. Multiple clinical and nutritional variables correlated with BMD z scores, but interpretation of these findings is complicated by covariance among variables. In stepwise regression analyses, it was found that severity of neurologic impairment as graded by Gross Motor Functional Classification level, increasing difficulty feeding the child, use of anticonvulsants, and lower triceps skinfold z scores (in decreasing order of importance) all independently contribute to lower BMD z scores in the femur. CONCLUSIONS: Low BMD is prevalent in children with moderate to severe CP and is associated with significant fracture risk. The underlying pathophysiology is complex, with multiple factors contributing to the problem and significant variation between different regions of the skeleton.