Preseason and midseason balance ability of professional Australian footballers

Balance ability has been shown to be important for sports performance and injury prevention. It is unclear whether balance ability changes due to sports participation and regular training without specific balance training. It has not been shown whether certain sports such as the various football codes that often involve single limb stance and balance as part of kicking, running, rapid changes of direction, jumping, and landing actually influence balance ability. The aim of this study was to determine whether there was a difference in balance ability measured at preseason and during the competitive season for elite footballer. Twenty-eight professional Australian footballers who did not undertake any specific balance training took part in this study. Postural sway from single limb balance on a force platform was measured for both limbs 1 week before the start and midway through a 22-week competitive season. The subjects were required to step onto a balance mat on top of the force platform and maintain balance for 20 seconds. The maximum sway of the center of pressure in the mediolateral direction was used as the balance score. It was found that there was not a significant difference in the balance ability measurement at the start and during the competitive season. Sports participation and regular training did not influence balance ability in this cohort of athletes.     

An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability

Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance.     

The influence of locomotor training on dynamic balance during steady-state walking post-stroke

Slow walking speed and lack of balance control are common impairments post-stroke. While locomotor training often improves walking speed, its influence on dynamic balance is unclear. The goal of this study was to assess the influence of a locomotor training program on dynamic balance in individuals post-stroke during steady-state walking and determine if improvements in walking speed are associated with improved balance control. Kinematic and kinetic data were collected pre- and post-training from seventeen participants who completed a 12-week locomotor training program. Dynamic balance was quantified biomechanically (peak-to-peak range of frontal plane whole-body angular-momentum) and clinically (Berg-Balance-Scale and Dynamic-Gait-Index). To understand the underlying biomechanical mechanisms associated with changes in angular-momentum, foot placement and ground-reaction-forces were quantified. As a group, biomechanical assessments of dynamic balance did not reveal any improvements after locomotor training. However, improved dynamic balance post-training, observed in a sub-group of 10 participants (i.e., Responders), was associated with a narrowed paretic foot placement and higher paretic leg vertical ground-reaction-force impulse during late stance. Dynamic balance was not improved post-training in the remaining seven participants (i.e., Non-responders), who did not alter their foot placement and had an increased reliance on their nonparetic leg during weight-bearing. As a group, increased walking speed was not correlated with improved dynamic balance. However, a higher pre-training walking speed was associated with higher gains in dynamic balance post-training. These findings highlight the importance of the paretic leg weight bearing and mediolateral foot placement in improving frontal plane dynamic balance post-stroke.     

Optimal matching with minimal deviation from fine balance in a study of obesity and surgical outcomes

In multivariate matching, fine balance constrains the marginal distributions of a nominal variable in treated and matched control groups to be identical without constraining who is matched to whom. In this way, a fine balance constraint can balance a nominal variable with many levels while focusing efforts on other more important variables when pairing individuals to minimize the total covariate distance within pairs. Fine balance is not always possible; that is, it is a constraint on an optimization problem, but the constraint is not always feasible. We propose a new algorithm that returns a minimum distance finely balanced match when one is feasible, and otherwise minimizes the total distance among all matched samples that minimize the deviation from fine balance. Perhaps we can come very close to fine balance when fine balance is not attainable; moreover, in any event, because our algorithm is guaranteed to come as close as possible to fine balance, the investigator may perform one match, and on that basis judge whether the best attainable balance is adequate or not. We also show how to incorporate an additional constraint. The algorithm is implemented in two similar ways, first as an optimal assignment problem with an augmented distance matrix, second as a minimum cost flow problem in a network. The case of knee surgery in the Obesity and Surgical Outcomes Study motivated the development of this algorithm and is used as an illustration. In that example, 2 of 47 hospitals had too few nonobese patients to permit fine balance for the nominal variable with 47 levels representing the hospital, but our new algorithm came very close to fine balance. Moreover, in that example, there was a shortage of nonobese diabetic patients, and incorporation of an additional constraint forced the match to include all of these nonobese diabetic patients, thereby coming as close as possible to balance for this important but recalcitrant covariate.     

Behavioral Assessment of the Aging Mouse Vestibular System

Age related decline in balance performance is associated with deteriorating muscle strength, motor coordination and vestibular function. While a number of studies show changes in balance phenotype with age in rodents, very few isolate the vestibular contribution to balance under either normal conditions or during senescence. We use two standard behavioral tests to characterize the balance performance of mice at defined age points over the lifespan: the rotarod test and the inclined balance beam test. Importantly though, a custom built rotator is also used to stimulate the vestibular system of mice (without inducing overt signs of motion sickness). These two tests have been used to show that changes in vestibular mediated-balance performance are present over the murine lifespan. Preliminary results show that both the rotarod test and the modified balance beam test can be used to identify changes in balance performance during aging as an alternative to more difficult and invasive techniques such as vestibulo-ocular (VOR) measurements.     

Dynamic balance during walking adaptability tasks in individuals post-stroke

Maintaining dynamic balance during community ambulation is a major challenge post-stroke. Community ambulation requires performance of steady-state level walking as well as tasks that require walking adaptability. Prior studies on balance control post-stroke have mainly focused on steady-state walking, but walking adaptability tasks have received little attention. The purpose of this study was to quantify and compare dynamic balance requirements during common walking adaptability tasks post-stroke and in healthy adults and identify differences in underlying mechanisms used for maintaining dynamic balance. Kinematic data were collected from fifteen individuals with post-stroke hemiparesis during steady-state forward and backward walking, obstacle negotiation, and step-up tasks. In addition, data from ten healthy adults provided the basis for comparison. Dynamic balance was quantified using the peak-to-peak range of whole-body angular-momentum in each anatomical plane during the paretic, nonparetic and healthy control single-leg-stance phase of the gait cycle. To understand differences in some of the key underlying mechanisms for maintaining dynamic balance, foot placement and plantarflexor muscle activation were examined. Individuals post-stroke had significant dynamic balance deficits in the frontal plane across most tasks, particularly during the paretic single-leg-stance. Frontal plane balance deficits were associated with wider paretic foot placement, elevated body center-of-mass, and lower soleus activity. Further, the obstacle negotiation task imposed a higher balance requirement, particularly during the trailing leg single-stance. Thus, improving paretic foot placement and ankle plantarflexor activity, particularly during obstacle negotiation, may be important rehabilitation targets to enhance dynamic balance during post-stroke community ambulation.     

Responsiveness to rehabilitation of balance and gait impairment in elderly with peripheral neuropathy

Elderly people with peripheral neuropathy of the lower limbs (PNLL) demonstrate a typical balance and gait impairment because of sensory ataxia. There is evidence that rehabilitation produces important gains on balance and gait. However, responsiveness to rehabilitation of balance and gait measures is unknown in PNLL. Aim of the current work is to evaluate the responsiveness to rehabilitation of balance, gait and sensory ataxia measures in elderly with PNLL.Twenty-five elderly with PNLL attending physiotherapy and occupational therapy during inpatient rehabilitation were recruited. Balance and gait measures (including static posturography, TUG test and the 10 m walking test) were administered on admission and discharge. An accelerometer secured to the trunk was used for TUG recording and static balance assessment. Static balance was tested with open and closed eyes, so as to assess sensory ataxia.Following rehabilitation, patients improved gait [admission vs discharge, mean(SD): 0.86(0.33) vs 0.98(0.32) m/s], TUG [18.7(7.8) vs 15.1(5.2) s] and turning [46.2(15.3) vs 53.3(15.3) °/s]. However, none of 12 static balance parameters derived from trunk acceleration significantly changed. Principal component analysis showed that before training, eyes closed and eyes open balance correlated with orthogonal components (one and two vs. three and four). After training, eyes open and eyes closed balance were more similar to each other being both correlated with component one.Responsiveness to rehabilitation is larger for gait than static balance measured by trunk acceleration. However, exercise can also have a beneficial effect on sensory ataxia by making eyes closed balance more similar to eyes open balance.     

Blood Pressure Associates with Standing Balance in Elderly Outpatients

Objectives

Assessment of the association of blood pressure measurements in supine and standing position after a postural change, as a proxy for blood pressure regulation, with standing balance in a clinically relevant cohort of elderly, is of special interest as blood pressure may be important to identify patients at risk of having impaired standing balance in routine geriatric assessment.

Materials and Methods

In a cross-sectional cohort study, 197 community-dwelling elderly referred to a geriatric outpatient clinic of a middle-sized teaching hospital were included. Blood pressure was measured intermittently (n = 197) and continuously (subsample, n = 58) before and after a controlled postural change from supine to standing position. The ability to maintain standing balance was assessed during ten seconds of side-by-side, semi-tandem and tandem stance, with both eyes open and eyes closed. Self-reported impaired standing balance and history of falls were recorded by questionnaires. Logistic regression analyses were used to examine the association between blood pressure and 1) the ability to maintain standing balance; 2) self-reported impaired standing balance; and 3) history of falls, adjusted for age and sex.

Results

Blood pressure decrease after postural change, measured continuously, was associated with reduced ability to maintain standing balance in semi-tandem stance with eyes closed and with increased self-reported impaired standing balance and falls. Presence of orthostatic hypotension was associated with reduced ability to maintain standing balance in semi-tandem stance with eyes closed for both intermittent and continuous measurements and with increased self-reported impaired standing balance for continuous measurements.

Conclusion

Continuous blood pressure measurements are of additional value to identify patients at risk of having impaired standing balance and may therefore be useful in routine geriatric care.     

Contribution of genetic and environmental effects to postural balance in older female twins.

The aim of the present study was to determine the relative roles of genetic and environmental influences on postural balance in older women. The participants were 97 monozygotic (MZ) and 102 dizygotic (DZ) female twins, aged 64-76 yr. Postural sway was measured during side-by-side stance with eyes open and eyes closed, and during semitandem stance with eyes open on a force platform. Sway data were condensed into four first-order and one second-order latent factors. The second-order factor, named balance, incorporates sway data from multiple tests and thus best describes the phenotype of postural balance. The contribution of genetic and environmental influences on the variability of the latent factors was assessed by using structural equation modeling. Additive genetic influences accounted for 35% and shared environmental influences accounted for 24% of the total variance in the balance factor. In the present study, postural balance in older women had a moderate genetic component. Genetic influences on postural balance may be mediated through gene variation in the systems that control posture. The finding that individual environmental influences accounted for almost one-half of the variance in postural balance points to the potential of targeted interventions to maintain and improve balance control in older persons.     

亚热带山区红壤地碳平衡研究进展

碳平衡研究日益成为全球变化与地球科学研究领域的热点问题.亚热带红壤区是我国发展粮食作物和各种热带、亚热带经济作物与林木的重要基地,因该区特殊的生态地理位置,在我国碳平衡研究中占有重要地位.本文论述了亚热带山区红壤地碳平衡研究的重要性,对碳平衡研究中植被、凋落物、土壤碳库和土壤呼吸的研究现状和主要结论等进行阐述,总结了碳平衡的综合研究方法,并对亚热带山区红壤地碳平衡研究中存在的问题和今后的发展方向进行探讨.     

A gravimetric system for lyophilized samples in the sub-microgram range

Summary A new quartz fiber balance is described which is evacuated and electrically shielded. This balance minimizes the problems of moisture uptake by the lyophilized sample, air convection inside the balance and static electricity. Besides it offers a wider useful weighing range and a higher handling comfort. It could be shown that in the regular (i.e. not evacuated) balance the moisture uptake varies considerably with the humidity of the air and with the kind of sample analyzed, and that it might be greater than previously reported.     

A recording plant transpiration balance

Transpiration rates, automatically monitored, provide a basis for investigating factors that affect the movement of water through plants and are particularly useful for demonstrating the role of leaf stoma. A transpiration balance is described which permits monitoring of transpiration rates by continuously recording the weight loss from a potted plant. It is based on the use of a displacement transducer to obtain a signal voltage output from an ordinary mechanical balance. Since it mainly incorporates equipment common to most laboratories, construction of the balance may involve relatively little expenditure. Experiments using the transpiration balance are presented and discussed.     

Validation of a posturographic approach to monitor sleepiness

Sleepiness is a major risk factor in traffic- and occupational accidents. While sleepiness is a persistent concern, there is no convenient test to monitor impending levels of sleepiness. We show that force platform posturographic balance testing addresses this need because it estimates time awake (TA) accurately and precisely. Testing the TA is appropriate because TA drives the sleep homeostatic process, a component in sleepiness. With 12 subjects we evaluated the accuracy and precision of repeated estimates of TA. Our extended study design that allows evaluating the accuracy and precision of posturographic TA-estimates is new. First, we tested the subjects’ balance every 2 h during 36 h of sustained wakefulness. This comprised the subjects’ reference curves (balance as a function of known and increasing TA). Then, we tested the subjects’ balance once a day over one week. We also tested the subjects’ balance once a week over one month. Finally, to estimate the subjects’ TA, we equated the balance scores with the scores in their reference curves. The accuracy of the estimates was 86%, and the precision was 97%. The high accuracy and precision of the estimates obtained with this one-month protocol validates the method of posturographic monitoring of sleepiness. So far, force platform posturographic balance testing has generally been used for clinical purposes, to quantify balance control and musculoskeletal performance. Our main result is that we now validated that balance testing provides accurate and precise estimates of TA, and hence, also provides an approach towards an automated monitor of sleepiness.     

A gravimetric system for lyophilized samples in the sub-microgram range.

A new quartz fiber balance is described which is evacuated and electrically shielded. This balance minimizes the problems of moisture uptake by the lyophilized sample, air convection inside the balance and static electricity. Besides it offers a wider useful weighing range and a higher handling comfort. It could be shown that in the regular (i.e. not evacuated) balance the moisture uptake varies considerably with the humidity of the air and with the kind of sample analyzed, and that it might be greater than previously reported.     

健康青年静态立位平衡功能的研究

目的:完善健康青年静态立位平衡参数常模和探讨人处于不利站立条件下姿势控制变化规律。方法:从某军校本科学员中随机抽取108名,对8种不同站立条件下的立位平衡功能进行测试,同时比较不同站立姿势下重心晃动的变化。结果:与睁眼站立相比,闭眼站立和闭眼站立于脚垫上,人体重心会不自主地向脚掌移动,同时重心晃动的轨迹长度和面积明显增加,而单位面积轨迹长度明显降低。另外,人体前后方向晃动的程度较大,而左右晃动的程度稍小。结论:健康人姿势控制由视觉、前庭和下肢本体感觉等共同维持的,任何系统受到限制,都会影响平衡功能。当人处于不利站立条件时,人的身体会本能地向前倾斜来维持平衡,同时本研究为涉及人体立位平衡方面的研究提供了新的研究方法和思路。     

Toward an understanding of the economics of pastoralism: The balance of exchange between pastoralists and nonpastoralists in Western Iran, 1815–1975

It has become a theoretical commonplace among students of southwest Asian pastoralism that the balance of exchange between pastoralists and their settled neighbors has had a profound effect on pastoralists, strongly influencing household viability and, indeed, the viability of pastoralism as an adaptation. However, little attempt has been made to examine historical variation in the balance of exchange. Attempts to use transformations in the balance of exchange as a means of accounting for change among pastoralists thus remain largely impressionistic and underspecified. This paper examines variations in the balance of exchange between Iranian pastoralists and non-pastoralists from 1815 to 1977. It demonstrates that to the degree that there were long term shifts in the balance of exchange, they favored pastoralists, and it argues that this trend became stronger, rather than weaker in the 20th century. This suggests that pressures on pastoralists over this period were not directly economic and that variation in the balance of exchange itself cannot account for outcomes such as the increased settlement of Iranian pastoralists.     

A new measure for upright stability

The control of balance is a primary objective in most human movements. In many cases, research or practice, it is essential to quantitatively know how good the balance is at a body posture or at every moment during a task. In this paper we suggest a new measure for postural upright stability which assigns a value to a body state based on the probability of avoiding a fall initiation from that state. The balance recovery problem is solved for a population sample using a strength database, and the probability of successfully maintaining the balance is found over the population and called the probability of recovery (PoR). It, therefore, describes an attribute of a body state: how possible the control of balance is, or how safe being at that state is. We also show the PoR calculated for a 3-link body model for all states on a plane, compare it to that found using a 2-link model, and compare it to a conventional metric: the margin of stability (MoS). It is shown, for example, that MoS may be very low at a state from which most of the people will be able to easily control their balance.     

拟自然水景的水均衡分析及水量设计研究

低影响设计和开发（LID）雨水资源,有助于水资源的保护和水景减量设计,形成具有自我调节能力的水景海绵体。将水均衡法运用于水景参数化设计中,构建拟自然水景水量平衡方程式,探寻汇水区雨水汇水量最佳值,进而为水景水量设计提供参考。由水均衡法核心思想质量守恒原理,即区域总输入水量等于总输出水量,提出拟自然水景水均衡分析方法,并以习水箐山森林公园主入口景观区为例,探讨水均衡分析在水景参数化设计中的应用。     

Modeling balance control during sustained waking allows posturographic sleepiness testing

We develop a method to quantify sleepiness. Sleepiness is a major risk factor in traffic and occupational accidents, but lack of convenient tests precludes monitoring impending sleepiness. Posturographic balance testing could address this need because sleepiness increases postural sway. It is, however, unclear how sleepiness influences balance control. Our results, for 12 subjects, show that balance control is more susceptible to increasing time awake (TA) compared to neuromuscular processes. This conclusion is reached since during sustained waking the control process slows down by 3.4% per hour of increased TA. This slowdown accounts for 65% of the variance in diurnal balance. We quantified balance control by modeling the body as an inverted pendulum and by expressing the control as the critical time interval for open-loop control (Deltat(c)) of the center-of-mass movements of this pendulum. To estimate the subjects' TA, we regressed the Deltat(c) scores recorded during sustained waking against increasing TA, and equated separate Deltat(c) test scores with the diurnal Deltat(c) scores. We estimated TA with 68% positive predictive value. The results encourage implementing balance modeling into a device that performs clinical or industrial balance testing because the model-based Deltat(c) score responded to increasing TA.