The common denominator in the assessment of human balance and posture is the inverted pendulum model. If we focus on appropriate versions of the model we can use it to identify the gravitational and acceleration perturbations and pinpoint the motor mechanisms that can defend against any perturbation.
We saw that in quiet standing an ankle strategy applies only in the A/P direction and that a separate hip load/unload strategy by the hip abd/adductors is the totally dominant defence in the M/L direction when standing with feet side by side. In other standing positions (tandem, or intermediate) the two mechanisms still work separately, but their roles reverse. In the tandem position M/L balance is an ankle mechanism (invertors/evertors) while in the A/P direction a hip load/unloading mechanism dominates.
During initiation and termination of gait these two separate mechanisms control the trajectory of the COP to ensure the desired acceleration and deceleration of the COM. During initiation the initial acceleration of the COM forward towards the stance limb is achieved by a posterior and lateral movement of the COP towards the swing limb. After this release phase there is a sudden loading of the stance limb which shifts the COP to the stance limb. The COM is now accelerated forward and laterally towards the future position of the swinging foot. Also M/L shifts of the COP were controlled by the hip abductors/adductors and all A/P shifts were under the control of the ankle plantar/dorsiflexors. During termination the trajectory of both COM and COP reverse. As the final weight-bearing on the stance foot takes place the COM is passing forward along the medial border of that foot. Hyperactivity of that foot's plantarflexors takes the COP forward and when the final foot begins to bear weight the COP moves rapidly across and suddenly stops at a position ahead of the future position of the COM. Then the plantarflexors of both feet release and allow the COP to move posteriorly and approach the COM and meet it as quiet stance is achieved. The inverted pendulum model permitted us to understand the separate roles of the two mechanisms during these critical unbalancing and rebalancing periods.
During walking the inverted pendulum model explained the dynamics of the balance of HAT in both the A/P and M/L directions. Here the model includes the couple due to the acceleration of the weight-bearing hip as well as gravitational perturbations. The exclusive control of A/P balance and posture are the hip extensors and flexors, while in the M/L direction the dominant control is with the hip abductors with very minor adductor involvement. At the ankle the inverted pendulum model sees the COM passing forward along the medial border to the weight-bearing foot. The model predicts that during single support the body is falling forward and being accelerated medially towards the future position of the swing foot. The model predicts an insignificant role of the ankle invertors/evertors in the M/L control. Rather, the future position of the swing foot is the critical variable or more specifically the lateral displacement from the COM at the start of single support. The position is actually under the control of the hip abd/adductors during the previous early swing phase.
The critical importance of the hip abductors/adductors in balance during all phases of standing and walking is now evident. This separate mechanism is important from a neural control perspective and clinically it focuses major attention on therapy and potential problems with some surgical procedures. On the other hand the minuscule role of the ankle invertors/evertors is important to note. Except for the tandem standing position these muscles have negligible involvement in balance control. 相似文献
Summary A simple model of the thorax, pelvis and three columns of the intrinsic lumbar back muscles (=ILBM) was constructed. The model was used to study the length of the ILBM during the different stages of the walking cycle. The length of the right ILBM (especially the lateral column) was largest at right toe off, exactly the stage of the walking cycle in which most force was needed to prevent the torso from falling forwards and laterally. 相似文献
This study aimed to determine whether changes in plasma heparin-releasable lipoprotein lipase (LPL) activity following a brisk
walk were associated with decreases in fasting and/or postprandial triglyceride (TG) concentrations. Two groups of pre-menopausal
women participated. In one group (fasting study group, n=10), TG concentrations and post-heparin plasma LPL activity were measured in the fasted state on two occasions: ~18 h after
a 2-h treadmill walk at 50% maximal oxygen uptake (exercise trial); and after a day of no exercise (control trial). The other
group (postprandial study group, n=9) undertook two oral fat tolerance tests (blood samples taken fasting and for 6 h after a high-fat meal), with plasma LPL
activity measured 6 h after meal ingestion. Pre-conditions were the same as for the fasting study group (i.e. control and
prior exercise). Prior exercise reduced fasting TG concentrations by 23 (7)% (fasting study group) [mean (SEM)] and by 18
(9)% (postprandial study group) (both P<0.05), and the postprandial TG response by 23 (6)% (postprandial study group) (P<0.01). Plasma LPL activity was not significantly increased by exercise in either the fasting or postprandial study groups.
However, exercise-induced changes in both fasting and postprandial LPL activity were significantly correlated with the respective
exercise-induced changes in fasting TG concentration and the postprandial TG response (r=−0.70 and −0.77 respectively, P<0.05 for both). These data suggest that increased LPL activity may contribute to the hypotriglyceridaemic effect of moderate
exercise, although other mechanisms are also likely to be involved.
Electronic Publication 相似文献
A shuttle cosmid vector, pANsCos1, has been constructed for Escherichia coli and filamentous fungi. This vector contains two cos sequences separated by a single XbaI restriction site. pANsCos1 allows the efficient construction of representative genomic libraries from as little as 15–20 g of genomic DNA. Due to the presence of a functional hygromycin B phosphotransferase gene (hph) transformation of fungal protoplasts with pANsCos1, or derivatives of it, results in the formation of hygromycin B-resistant transformants. The T7 and T3 RNA polymerase promoter sequences flanking the cloning site, in combination with two adjacent NotI sites facilitate genomic walking and the rapid construction of restriction maps of cloned inserts.Dedicated to Professor Dr. K. Esser on the occasion of his 70th birthday 相似文献
IntroductionStroke is the leading cause of non-traumatic disability in adults, with balance and gait disturbances representing the main limitations of body functions. Dance therapy (DT) has shown positive effects in older adults and in patients with neurological pathologies. This systematic review aims to examine the feasibility, acceptability and effects of DT in stroke rehabilitation, specifically on functional gains of gait and balance.MethodsA systematic search was carried out for articles published in the MEDLINE, PEDro, Web of Science, Scopus and CINHAL in February 2021 and updated in April 2021. Results: Eight studies were included (2 clinical cases, 5 case series and 1 randomized controlled trial), 7 of them in patients with chronic stroke and only 1 in subacute stroke phase. The most widely used dance modality was tango and ballet, with sessions ranging from 30 to 110 min. DT seems to show positive effects on post-stroke body functions and activities such as gait and balance. Reported dropout rates are inconsistent, no adverse effects were reported, and participant satisfaction was high.ConclusionGiven the heterogeneity and uneven quality of the included studies, strong conclusions cannot be put forward on the effectiveness of DT in post-stroke body function and activities. Nevertheless, DT seems to be safe and acceptable therapy for patients, and no adverse effects have been reported. More studies with a high level of evidence and feasibility are needed to determine the patient profile, the characteristics of the intervention, the participation rate and the role of the rehabilitation professional most likely to generate optimal benefit. 相似文献
This study assessed behavioural and neurochemical effects of i.c.v. injections of both the cholinergic toxin 192 IgG-saporin (2 microgram) and the serotonergic toxin 5,7-dihydroxytryptamine (5,7-DHT; 150 microgram) in Long-Evans female rats. Dependent behavioural variables were locomotor activity, forced T-maze alternation, beam walking, Morris water-maze (working and reference memory) and radial-maze performances. After killing by microwave irradiation, the concentrations of acetylcholine, monoamines and 5-hydroxyindoleacetic acid (5-HIAA) were measured in the hippocampus, frontoparietal cortex and striatum. 192 IgG-saporin reduced the concentration of acetylcholine by approximately 40% in the frontoparietal cortex and hippocampus, but had no effect in the striatum. 5,7-DHT lesions reduced the concentration of serotonin by 60% in the frontoparietal cortex and 80% in the hippocampus and striatum. Noradrenaline was unchanged in all structures except the ventral hippocampus where it was slightly increased in rats given 192 IgG-saporin. Cholinergic lesions induced severe motor deficits but had no other effect. Serotonergic lesions produced diurnal and nocturnal hyperactivity but had no other effect. Rats with combined lesions were more active than those with only serotonergic lesions, showed motor dysfunctions similar to those found in rats with cholinergic lesions alone, and exhibited impaired performances in the T-maze alternation test, the water-maze working memory test and the radial-maze. Taken together and although cholinergic lesions were not maximal, these data show that 192 IgG-saporin and 5,7-DHT lesions can be combined to selectively damage cholinergic and serotonergic neurons, and confirm that cholinergic-serotonergic interactions play an important role in some aspects of memory, particularly in spatial working memory. 相似文献
BACKGROUND: Previous mobility studies have used Preferred Walking Speed (PWS) in order to determine the walking efficiency in terms of the Percent Preferred Walking Speed (PPWS) of visually impaired adults. PWS has been measured in previous studies using the sighted guide (SG) and non-sighted guide (NSG) techniques. This study compared the NSG, SG and string (ST) (subjects walked by holding on lightly to a cardboard tube attached to a piece of string) techniques of measuring PWS in visually impaired subjects. METHODS: Forty visually impaired subjects with central and peripheral vision loss were recruited. PWS was measured using the NSG, SG and ST techniques. For each technique, PWS was determined by recording the time taken for a subject to walk an unobstructed, straight 20-m corridor. RESULTS: There were no significant differences in PWS using the SG, NSG and ST techniques. CONCLUSION: For assessing walking efficiency, either the SG, NSG or ST technique could be employed when measuring PWS in visually impaired subjects. 相似文献