date: 12/01/1964
author: Miller PB, Johnson RL, Lamb Le.
publication: Aerosp Med. 1964 Dec;35:1194-200.
pubmed_ID: 14230666
Category: Research and Articles
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.
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.
Alternate leg movement amplifies locomotor-like muscle activity in spinal cord injured persons.
date: 02/01/2005
author: Kawashima N, Nozaki D, Abe MO, Akai M, Nakazawa K.
publication: J Neurophysiol. 2005 Feb;93(2):777-85. Epub 2004 Sep 22.
pubmed_ID: 15385590
It is now well recognized that muscle activity can be induced even in the paralyzed lower limb muscles of persons with spinal cord injury (SCI) by imposing locomotion-like movements on both of their legs. Although the significant role of the afferent input related to hip joint movement and body load has been emphasized considerably in previous studies, the contribution of the “alternate” leg movement pattern has not been fully investigated. This study was designed to investigate to what extent the alternate leg movement influenced this “locomotor-like” muscle activity. The knee-locked leg swing movement was imposed on 10 complete SCI subjects using a gait training apparatus. The following three different experimental conditions were adopted: 1) bilateral alternate leg movement, 2) unilateral leg movement, and 3) bilateral synchronous (in-phase) leg movement. In all experimental conditions, the passive leg movement induced EMG activity in the soleus and medial head of the gastrocnemius muscles in all SCI subjects and in the biceps femoris muscle in 8 of 10 SCI subjects. On the other hand, the EMG activity was not observed in the tibialis anterior and rectus femoris muscles. The EMG level of these activated muscles, as quantified by integrating the rectified EMG activity recorded from the right leg, was significantly larger for bilateral alternate leg movement than for unilateral and bilateral synchronous movements, although the right hip and ankle joint movements were identical in all experimental conditions. In addition, the difference in the pattern of the load applied to the leg among conditions was unable to explain the enhancement of EMG activity in the bilateral alternate leg movement condition. These results suggest that the sensory information generated by alternate leg movements plays a substantial role in amplifying the induced locomotor-like muscle activity in the lower limbs.
Skeletal adaptations to alterations in weight-bearing activity: a comparison of models of disuse osteoporosis.
date: 01/01/2001
author: Giangregorio L, Blimkie CJ.
publication: Sports Med. 2002;32(7):459-76.
pubmed_ID: 12015807
The removal of regular weight-bearing activity generates a skeletal adaptive response in both humans and animals, resulting in a loss of bone mineral. Human models of disuse osteoporosis, namely bed rest, spinal cord injury and exposure to micro-gravity demonstrate the negative calcium balance, alterations in biochemical markers of bone turnover and resultant loss of bone mineral in the lower limbs that occurs with reduced weight-bearing loading. The site-specific nature of the bone response is consistent in all models of disuse; however, the magnitude of the skeletal adaptive response may differ across models. It is important to understand the various manifestations of disuse osteoporosis, particularly when extrapolating knowledge gained from research using one model and applying it to another. In rats, hindlimb unloading and exposure to micro-gravity also result in a significant bone response. Bone mineral is lost, and changes in calcium metabolism and biochemical markers of bone turnover similar to humans are noted. Restoration of bone mineral that has been lost because of a period of reduced weight bearing may be restored upon return to normal activity; however, the recovery may not be complete and/or may take longer than the time course of the original bone loss. Fluid shear stress and altered cytokine activity may be mechanistic features of disuse osteoporosis. Current literature for the most common human and animal models of disuse osteoporosis has been reviewed, and the bone responses across models compared.
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.
Standing and its importance in spinal cord injury management.
date: 01/01/1987
author: Axelson P, Gurski D, Lasko-Harvill A.
publication: RESNA 10th Annual Conference San Jose, California 1987
pubmed_ID:
Outside_URL:
A broad spectrum of physiological problems are associated with lack of gravitational stress in the individual with spinal cord injury. Prolonged immobilization results in systemic de-adaptations which include cardiovascular changes, the alteration of calcium homeostasis which leads to bone de-mineralization and risk of urinary calculi.
Weight bearing in the standing posture has been shown to ameliorate many of these problems and offers physiological advantages for the individual with spinal card injury.
There are also significant psychological and social benefits to standing, including improved self-image, and eye-to-eye interpersonal contact. Increased vocational, recreational and daily living independence are additional benefits of standing.
Bone loss and muscle atrophy in spinal cord injury: epidemiology, fracture prediction, and rehabilitation strategies.
date: 01/01/2006
author: Giangregorio L, McCartney N.
publication: J Spinal Cord Med. 2006;29(5):489-500.
pubmed_ID: 17274487
Individuals with spinal cord injury (SCI) often experience bone loss and muscle atrophy. Muscle atrophy can result in reduced metabolic rate and increase the risk of metabolic disorders. Sublesional osteoporosis predisposes individuals with SCI to an increased risk of low-trauma fracture. Fractures in people with SCI have been reported during transfers from bed to chair, and while being turned in bed. The bone loss and muscle atrophy that occur after SCI are substantial and may be influenced by factors such as completeness of injury or time post injury. A number of interventions, including standing, electrically stimulated cycling or resistance training, and walking exercises have been explored with the aim of reducing bone loss and/or increasing bone mass and muscle mass in individuals with SCI. Exercise with electrical stimulation appears to increase muscle mass and/or prevent atrophy, but studies investigating its effect on bone are conflicting. Several methodological limitations in exercise studies with individuals with SCI to date limit our ability to confirm the utility of exercise for improving skeletal status. The impact of standing or walking exercises on muscle and bone has not been well established. Future research should carefully consider the study design, skeletal measurement sites, and the measurement techniques used in order to facilitate sound conclusions.
Can Using Standers Increase Bone Density In Non-Ambulatory Children?
date: 10/01/2006
author: Katz, Danielle,MD, Snyder, Bryan MD, PhD, Dodek, Anton MD, Holm, Ingrid MD Miller, Claire BS
publication: Abstract as published in the American Academy of Cerebral Palsy and Developmental Medicine (AACPDM) 2006 Conference Proceedings
Purpose: Pathologic fractures are a significant source of morbidity for non-ambulatory children with neuromuscular dysfunction. We hypothesize that increasing weight-bearing in non-ambulatory children will increase bone material density (BMD) and decrease fracture risk. The aim of this pilot study was to demonstrate that non-ambulatory children participating in a standing program for at least two hours a day will experience an increase in BMD in the weight bearing bones. We also evaluate the reliability of measuring BMD at the calcaneous (weight bearing bones) and distal forearm (non-weight bearing bone) using peripheral DXA in delayed, non-ambulatory children.
Methods: After receiving IRB approval, 12 non-ambulatory, quadriplegic children (ages 12-21) consented to participate in a 2 hour/day, 5 day/week standing program. A history, orthopaedic exam, determination of bone age, laboratory tests for metabolic bone disease and BMD at the calcaneal tuberosity and distal forearm metaphyses were obtained. Compliance with the prescribed standing program was monitored for 6 months. BMD was measured using peripheral DXA at baseline and every 3 months. Using Jan. 2003 BMD data as a baseline, the ratio of change in BMD at the calcaneous and distal forearm was evaluated as a function of percent compliance with standing program.
Results: Intrarater reliability for BMD measured by peripheral DXA was good: Pearson correlation for the calcaneous = 0.90 (p=0.01) and for the forearm = 0.96 (p=0.01). Paired t test between two sets of data measured at each site on the same day were not different for calcaneous (t=0.92, df=15, p=0.37) or forearm (t=0.05, df=15, p=0.96). Compliance with the standing program was inconsistent. No patients were 100% compliant. Patients tended to stand longer at the initiation of the study Jan.-April (Jan vs Apr, p = 0.018; Jan vs Jul, p = 0.89; Apr vs Jul, p = 0.063). Compliance (%) was positively correlated (r = -0.62) with increased calcaneous BMD measured in April. This is in contrast to forearm BMD measured at the same time; which was negatively correlated (r = -0.44) with standing compliance. This support the notion that standing preferentially increases bone mass in the weight-bearing bones. However the BMD at the calcaneous measured in July was decreased, perhaps reflecting the decreased compliance the with standing program over the succeeding interval April-July.
Conclusion: It is feasible to have non-ambulatory children participate in a rigorous standing program. The weight bearing ?dose? affects BMD at the calcaneous but the benefit appears to be transient if the intensive standing program is not sustained.
Significance: The intensive use of standers (10 hours/wk) may have a beneficial effect on BMD of weight bearing bones in non-ambulatory children.
Physiologic responses to electrically assisted and frame-supported standing in persons with paraplegia.
date: 12/01/2003
author: Jacobs PL, Johnson B, Mahoney ET.
publication: J Spinal Cord Med. 2003 Winter;26(4):384-9.
pubmed_ID: 14992341
BACKGROUND: Systems of functional electrical stimulation (FES) have been demonstrated to enable some persons with paraplegia to stand and ambulate limited distances. However, the energy costs and acute physiologic responses associated with FES standing activities have not been well investigated. OBJECTIVE: To compare the physiologic responses of persons with paraplegia to active FES-assisted standing (AS) and frame-supported passive standing (PS). METHODS: Fifteen persons with paraplegia (T6-T11) previously habituated to FES ambulation, completed physiologic testing of PS and AS. The AS assessments were performed using a commercial FES system (Parastep-1; Altimed, Fresno, Calif); the PS tests used a commercial standing frame (Easy Stand 5000; Altimed, Fresno, Calif). Participants also performed a peak arm-cranking exercise (ACE) test using a progressive graded protocol in 3-minute stages and 10-watt power output increments to exhaustion. During all assessments, metabolic activity and heart rate (HR) were measured via open-circuit spirometry and 12-lead electrocardiography, respectively. Absolute physiologic responses to PS and AS were averaged over 1-minute periods at 5-minute intervals (5, 10, 15, 20, 25, and 30 minutes) and adjusted relative to peak values displayed during ACE to determine percentage of peak (%pk) values. Absolute and relative responses were compared between test conditions (AS and PS) and across time using two-way analysis of variance. RESULTS: The AS produced significantly greater values of VO2 (43%pk) than did PS (20%pk). The mean HR responses to PS (100-102 beats per minute [bpm] throughout) were significantly lower than during AS, which ranged from 108 bpm at 5 minutes to 132 bpm at test termination. CONCLUSION: Standing with FES requires significantly more energy than does AS and may provide a cardiorespiratory stress sufficient to meet minimal requirements for exercise conditioning.