模拟飞行任务负荷对人体姿势控制的影响

目的:研究在机体不同站立姿势下,模拟飞行任务负荷对姿势控制能力的影响,并初步总结其变化规律。方法:从某航空院校学员中随机抽取30名,要求其持续进行4小时的模拟飞行任务负荷,并同时在0 h、1 h、2 h、3 h与4 h时,测试4种不同站立姿势下的静态立位平衡参数,比较不同姿势晃动的变化规律。结果:随着模拟飞行任务的持续,4种站立姿势下,被试的立位平衡能力发生了不同程度的变化,并呈现出一定的变化趋势。其中睁眼站立于脚垫上的姿势晃动程度变化最明显,并有重心前倾的趋势;另外,在暴露于飞行任务负荷下,机体视觉信息通道的关闭有可能激发视觉、前庭、本体与肌肉控制等系统对平衡维持能力的代偿性增强作用,而下肢本体感觉信息的阻碍又同时会损坏视觉、前庭、本体等系统对立位平衡能力的控制作用。结论:模拟飞行任务负荷下,机体的姿势晃动会呈现一定的变化规律,即身体可能会代偿性的向前倾斜,来维持身体的立位平衡状态。同时,视觉通道与下肢本体感觉通道对任务负荷条件下立位平衡功能的代偿能力发挥不同的作用。这种变化规律的初步阐述对我们下一步的立位平衡与飞行疲劳评估的研究打下一定的理论基础。     

精神疲劳状态下脑组织血氧饱和度的近红外光谱分析

目的:研究精神疲劳状态下脑组织血氧饱和度的变化规律。方法:从某军校随机抽取25名被试,采用模拟飞行任务负荷构建精神疲劳模型,采用NASA-TLX量表评价模型。实验全程使用近红外光谱技术对被试脑组织血氧饱和度进行实时监测;实验前后分别对被试的作业绩效水平进行评估。结果:任务后NASA-TLX量表评分明显高于任务前(P0.01);任务前后作业绩效发生变化,反应能力测试的正确率下降(P0.01),错误率上升(P0.01);任务负荷后脑组织血氧饱和度相对于静息状态升高(P0.05)。结论:精神疲劳状态会影响被试的作业绩效。疲劳后脑组织血氧饱和度水平受被试动机以及代偿机制的影响高于静息水平。     

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。     

静态负荷家免血清生物标志酶及能量代谢的变化

目的:探讨静态负荷致骨骼肌损伤的机制.方法:观察2种不同姿势静态负荷下血清肌酸激酶(CK)、乳酸脱氢酶(LDH)和乳酸(LD)、血糖在0 h、2 h、4 h、6 h、8 h的变化.结果:血清CK、LDH、LD、血糖含量有差异(P<0.05或P<0.01).结论:长时间静态体位,骨骼肌损伤程度与负荷持续时间、负荷强度有关,损伤原因与能量代谢发生障碍有关.     

温光条件与寒地水稻产量和源库特征的关系

采用大田试验,以寒地水稻为研究对象,分析试验区2011—2014年气温和太阳辐射,比较不同年份间温光条件差异,探讨温光条件与水稻干物质积累、源库光合特征、产量及其构成之间的关系。结果表明:生育期内日活动积温利用率和日有效积温利用率呈逐年增加的趋势,而太阳辐射呈逐年降低的趋势,其中灌浆期太阳辐射强度以2014年居高;生育期内日活动积温和日有效积温及其利用率、抽穗后日平均太阳辐射强度与粒数、结实率、千粒重以及产量显著或极显著正相关;生育期内活动积温与产量(R~2=0.69)、生物产量(R~2=0.49)、抽穗期茎鞘干质量(R~2=0.74)及粒叶比(R~2=0.34)、收获指数(R~2=0.63)、群体生长速率(R~2=0.78)和净同化率(R~2=0.73)均呈二次函数关系,且拟合效果均达极显著水平,而与叶面积指数呈极显著正相关关系(R=0.80)。     

静态负荷诱发肌肉疲劳后恢复期sEMG信号变化规律

目的:探讨肌肉疲劳过程中sEMG功率谱变化与H 的关系以及可能存在的其它影响因素.方法:利用肌肉进行疲劳收缩结束后,短时间内肌肉pH值尚无明显改变的特性,观察恢复期30 s内s EMG功率谱的变化规律.八名男性受试者,以肱二头肌为目标肌肉,负荷强度为60%MVC,静态持续负荷至疲劳点后,在恢复期以同样负荷分别观察2 s、4 s、6 s、8 s、10 s、20 s、30 s时的sEMG信号特征.结果:肱二头肌在以60%MVC静态疲劳负荷过程中MPF呈线性下降.在疲劳负荷后的恢复期,MPF恢复极其迅速,运动结束后仅2 s,MPF已恢复到整个下降范围的26.5%;至30 s,MPF已恢复到整个下降范围的87.7%.结论:由[H ]增加引起的肌纤维动作电位传导速度下降不是决定sEMG功率谱左移的唯一因素,提示sEMG功率谱左移可能与神经源性的中枢机制的作用有关.     

利用异速生长关系和地统计方法估算武夷山南麓毛竹林生物量

澄清毛竹(Phyllostachys edulis)生物量与胸径之间的异速生长关系及毛竹林生物量密度与叶面积指数之间的关系有助于准确估算毛竹林生物量。本文结合异速生长关系和地统计方法对中尺度毛竹林生物量进行估算。利用收获法在武夷山南麓毛竹林分布区砍伐103棵标准竹,并用冠层分析仪获取毛竹林叶面积指数,建立毛竹生物量与胸径、林分生物量密度与叶面积指数的异速生长关系;再利用地统计方法对黄坑镇毛竹林生物量的空间分布进行模拟。结果表明:武夷山南麓毛竹单株生物量与胸径之间存在明显的幂函数关系(R~2=0.585,P=0.002);毛竹林生物量密度与叶面积指数间也存在着显著的幂函数关系(R~2=0.525,P=0.002);利用建立的异速生长方程和地统计方法对黄坑镇毛竹林地上生物量的模拟结果表明,黄坑镇毛竹林平均地上生物量密度为53.49 t·hm~(-2),全镇毛竹林地上生物量约为0.62 Tg。     

生理节律与日常活动对人体疲劳程度的影响

目的:研究生理节律和日常活动分别对人体疲劳程度的影响大小。方法:选取某校7名大学生志愿者,在军训期间对每日军训科目严格限制条件下进行该实验,以闪光临界融合频率、心率变异性、反应时、静态姿势图TLX-NASA量表评分作为指标,对每天分别在训练前和训练后疲劳程度的大小进行测量,以这些指标描述训练前后的疲劳程度。结果:反应时降低(0.60±0.09)、反应正确率提高(0.97±0.03);闪光临界光融合频率升高(40.84±2.14);心率变异性TP(3076.60±382.08)降低、心率变异性SDNN(55.28±16.85)降低;静态姿势图晃动减少,中低频率段(0.15±0.01)、前后方向重心变位(7.92±0.63),TLX-NASA量表评分降低(30.47±10.23)。以上差异均具有统计学意义(P<0.05)。结论:生理节律相对于日常活动对机体的疲劳状态有更大的影响。     

人工模拟降水条件下旱作农田土壤“Birch效应”及其响应机制

降水事件引起干土复湿刺激土壤CO_2,脉冲释放的现象被称为"Birch效应",其作用机制可能是降水刺激土壤"底物供给"增加或引起土壤"微生物胁迫"所致。为深入了解土壤"Birch效应"对降水格局改变的响应过程及内在机制,在冬小麦拔节期和夏闲期分别进行了不同降水量(1-32 mm)人工模拟降水实验,系统观测了降水后0-72 h土壤呼吸及土壤碳组分变化特征,结果表明:土壤呼吸随降水量的增大而增强,1-16 mm降水土壤呼吸峰值出现在降水后4h,而32 mm降水土壤呼吸峰值出现时间滞后了4 h。与较小降水量相比,较大的降水量能增加土壤呼吸但会推迟土壤呼吸峰值出现时间。土壤呼吸速率峰值(SRP)与降水量(P)呈幂相关(拔节期:SR-P=0.97P~(0.09),R~2=0.5,P0.05;夏闲期:SR-P=1.07P~(0.09),R~2=0.98,P0.01)。降水后72h累积CO_2释放量(CO_2-P)与降水量呈线性相关(拔节期:CO_2-P=0.03P+5.99,R~2=0.58,P0.05;夏闲期:CO_2-P=0.11P+6.04,R~2=0.86,P0.01)。土壤呼吸温度敏感性系数和降水量之间存在二次曲线关系(拔节期:Q_(10)=-0.007P~2+0.2P+0.7,R~2=0.32,R~20.05;夏闲期:Q_(10)=-0.01P~2+0.3P+0.2,R~2=0.86,P0.01)。逐步回归分析表明,冬小麦拔节期所有降水量处理土壤呼吸与土壤微生物量碳相关性均达到显著水平(P0.05),指示土壤"Birch效应"是由"微生物胁迫"所致。而在夏闲期,当降水量小于8 mm时土壤呼吸与微生物量碳相关性显著,即以微生物胁迫机制占主导;8 mm降水处理下土壤呼吸与氯仿熏蒸-K_2SO_4提取态有机碳相关性达到极显著水平,指示则为两种机制共同起作用,而当降水量大于16 mm时,土壤呼吸主要与可提取态有机碳显著相关,"Birch"效应转为以底物供给机制占主导。与夏闲期相比,冬小麦拔节期作物生长会削弱"Birch效应",并改变其响应机制。     

精神疲劳评价方法研究进展

长时间飞行活动所致的精神疲劳一直是航空航天医学中一个重要的课题。尤其随着我军航空技术的发展,精神疲劳已经成为影响飞行安全的重要原因之一。研究发现,精神疲劳发生时,机体的生理、心理、生化和工作绩效等功能会发生变化。例如,精神疲劳时,脑电图的theta波、delta波和alpha波发生变化、瞳孔直径增大、心率变异性的低频谱功率升高和高频谱功率降低、姿势控制能力下降、反应时延长、临界融合频率降低、血浆中氨基酸等功能性分子水平改变和认知能力的下降等。精神疲劳的客观评定方法就是研究者借助于某些设备来监测到这些变化,并根据这些变化对疲劳状态进行判断。本文将从生理、心理、生化和作业绩效等方面阐述了精神疲劳客观的评定方法,并指出了这些方法的优缺点。最后,本文对精神疲劳评价方法发展趋势做出了初步的判断,即我们应对精神疲劳进行综合量化评定,这样才能更全面准确地评估精神疲劳。     

Reciprocal influences on performances of a postural–suprapostural task by manipulating the level of task-load

The objective of this study was to investigate the reciprocal influences of stance pattern (bilateral stance vs. unilateral stance) and thumb-index precision grip task (static target vs. dynamic target) on postural–suprapostural tasks by manipulating task-load. Fifteen healthy volunteers participated in four postural–suprapostural tasks, including static force-matching in bilateral/unilateral stance (BS_static; US_static), dynamic force-matching in bilateral/unilateral stance (BS_dynamic; US_dynamic), and two control tasks in bilateral and unilateral stances without a finger task. The normalized force error (NFE), reaction time (RT) of the finger tasks, and normalized change in center of pressure sway (ΔNCoP) were measured. For suprapostural task performance, a significant interaction effect between postural and suprapostural tasks on NFE of the finger tasks was noted (static: BS < US; dynamic: BS > US), but RT was not different among the four tasks. For postural task performance, negative ΔNCoP during unilateral stance indicated a spontaneous reduction in postural sway due to added force-matching. In contrast, addition of force-matching tended to increase postural sway during bilateral stance, but postural fluctuations decreased as task-load of suprapostural task increased (BS_dynamic < BS_static). In conclusion, performance of postural–suprapostural tasks was differently modulated by task-load increment. Our observations favored adaptive resource-sharing and implicit expansion of resource capacity for a postural task with a motor suprapostural goal.     

Age Effects on Mediolateral Balance Control

BackgroundAge-related balance impairments, particularly in mediolateral direction (ML) may cause falls. Sufficiently sensitive and reliable ML balance tests are, however, lacking. This study is aimed to determine (1) the effect of age on and (2) the reliability of ML balance performance using Center of Mass (CoM) tracking.MethodsBalance performance of 19 young (26±3 years) and 19 older (72±5 years) adults on ML-CoM tracking tasks was compared. Subjects tracked predictable and unpredictable target displacements at increasing frequencies with their CoM by shifting their weight sideward. Phase-shift (response delay) and gain (amplitude difference) between the CoM and target in the frequency domain were used to quantify performance. Thirteen older and all young adults were reassessed to determine reliability of balance performance measures. In addition, all older adults performed a series of clinical balance tests and conventional posturography was done in a sub-sample.ResultsPhase-shift and gain dropped below pre-determined thresholds (−90 degrees and 0.5) at lower frequencies in the older adults and were even lower below these frequencies than in young adults. Performance measures showed good to excellent reliability in both groups. All clinical scores were close to the maximum and no age effect was found using posturography. ML balance performance measures exhibited small but systematic between-session differences indicative of learning.ConclusionsThe ability to accurately perform ML-CoM tracking deteriorates with age. ML-CoM tracking tasks form a reliable tool to assess ML balance in young and older adults and are more sensitive to age-related impairment than posturography and clinical tests.     

Motor Learning: An Analysis of 100 Trials of a Ski Slalom Game in Children with and without Developmental Coordination Disorder

ObjectiveAlthough Developmental Coordination Disorder (DCD) is often characterized as a skill acquisition deficit disorder, few studies have addressed the process of motor learning. This study examined learning of a novel motor task; the Wii Fit ski slalom game. The main objectives were to determine: 1) whether learning occurs over 100 trial runs of the game, 2) if the learning curve is different between children with and without DCD, 3) if learning is different in an easier or harder version of the task, 4) if learning transfers to other balance tasks.Method17 children with DCD (6–10 years) and a matched control group of 17 typically developing (TD) children engaged in 20 minutes of gaming, twice a week for five weeks. Each training session comprised of alternating trial runs, with five runs at an easy level and five runs at a difficult level. Wii scores, which combine speed and accuracy per run, were recorded. Standardized balance tasks were used to measure transfer.ResultsSignificant differences in initial performance were found between groups on the Wii score and balance tasks. Both groups improved their Wii score over the five weeks. Improvement in the easy and in the hard task did not differ between groups. Retention in the time between training sessions was not different between TD and DCD groups either. The DCD group improved significantly on all balance tasks.ConclusionsThe findings in this study give a fairly coherent picture of the learning process over a medium time scale (5 weeks) in children novice to active computer games; they learn, retain and there is evidence of transfer to other balance tasks. The rate of motor learning is similar for those with and without DCD. Our results raise a number of questions about motor learning that need to be addressed in future research.     

The effect of various degrees of foot posture on standing balance in a healthy adult population

Abstract

Purpose: Foot biomechanics plays a significant role in the quality of standing and walking. It has been believed that even minor biomechanical alterations in the foot support surface may influence strategies to maintain body standing balance. Hence, the aim of this study was to investigate the role of various degrees of foot posture on static and dynamic standing balance components in a healthy adult population.

Subjects and methods: A convenience sample of 41 healthy adult subjects with a mean age of 24.3?±?6.4 years and a body mass index (BMI) of 29?kg/m² participated in this study. On the basis of foot posture index (FPI), the participants were allocated into either group A or B. Group A included 16 subjects with an FPI range of 6–11 whereas group B included 25 subjects with an FPI range of 0–5. Standing balance components were analyzed using computerized dynamic posturography (CDP) by the Modified Clinical Test of Sensory Interaction on Balance (mCTSIB) and the limit of stability (LOS).

Results: Spearman’s correlation coefficient showed a significant correlation between the standing dynamic balance and FPI in group B but not in group A. Moreover, it also showed no significant correlation between the standing static balance component and FPI in either group A or B.

Conclusion: This study concluded that higher degrees of FPI might have an effect on standing dynamic balance in healthy subjects. These components may require extra attention during the preventive aspects of rehabilitation.     

The Role of Therapy Dogs in Speed and Accuracy to Complete Motor Skills Tasks for Preschool Children

ABSTRACT

The purpose of this study was to determine whether the presence of a therapy dog would affect the performance of a set of gross motor skills tasks for a mixed group of language-impaired and typical preschool children. The 14 children in the group were between four and six years old (four female and ten male); the two dogs were Miniature Poodles. The design was a two-way mixed model factorial, where a series of 10 gross motor skills tasks (e.g., long jump, high jump—labeled Type of Task) performed by the children served as one variable, and the presence or absence of the therapy dog (labeled Dog Presence) served as the other variable. In the dog-present conditions, the dog either performed the task immediately prior to, or at the same time as, the child. Time to complete each task and the accuracy of task performance as determined by a rating scale were determined from a review of experiment videotapes. The main effect of Dog Presence was significant (F_(1,36) = 7.471, p < 0.05, R² = 0.17). As predicted, the children completed the tasks faster when the dog was present (M = 10.88 s,SD = 9.84) than when the dog was absent (M = 13.86 s,SD = 12.64), but this effect was not present in the ratings data. This indicates that the presence of a therapy dog served as an effective motivator for the children, who performed faster, but without compromising accuracy, in all tasks but one. The interaction between dog presence and type of task was also significant (F_(9,71) = 3.67, p < 0.05, R² = 0.32) in the ratings data, indicating that the presence of the dog increased performance accuracy in some types of tasks, while decreasing it in others. Based on these results and the strong connection between motor skills and language development, the authors recommend a role for therapy dogs in speech and language development programs for preschool children.     

Does Dysphoria Lead to Divergent Mental Fatigue Effects on a Cognitive Task?

Objective

Tiredness, low energy, and listlessness are common symptoms to be associated with depression. The question remains to what extent these symptoms influence the effects of fatigue on sustained performance tasks, such as impaired task engagement and performance. Based on earlier findings, it was hypothesized that dysphoric (i.e., mildly depressed) individuals, compared to healthy controls, would display earlier fatigue onset and more severe fatigue effects on task engagement and performance during a cognitive task.

Methods

Sixty-one dysphoric and twenty-one non-dysphoric control participants were compared during one hour of continuous performance on a 2-back task. During the task subjective fatigue, subjective engagement, objective task performance, baseline pupil diameter and stimulus-evoked pupil dilation were measured.

Results

While we found that the dysphoric group reported relatively higher subjective fatigue than the healthy control group at the start of the experiment, we did not find any other divergent fatigue effects during the experimental task.

Conclusion

One explanation for the absence of divergent effect is that dysphoria may not have such a profound impact on available cognitive resources, like attention, as initially thought. Based on the results of the present study, we conclude that dysphoria is not necessarily an increased risk factor for impaired sustained performance on cognitive tasks that may induce mental fatigue.     

Reliability of high-density surface electromyography for assessing characteristics of the thoracic erector spinae during static and dynamic tasks

PurposeTo establish intra- and inter-session reliability of high-density surface electromyography (HDEMG)-derived parameters from the thoracic erector spinae (ES) during static and dynamic goal-directed voluntary movements of the trunk, and during functional reaching tasks.MethodsTwenty participants performed: 1) static trunk extension, 2) dynamic trunk forward and lateral flexion, and 3) multidirectional functional reaching tasks on two occasions separated by 7.5 ± 1.2 days. Muscle activity was recorded bilaterally from the thoracic ES. Root mean square (RMS), coordinates of the barycentre, mean frequency (MNF), and entropy were derived from the HDEMG signals. Reliability was determined with intraclass correlation coefficient (ICC), coefficient of variation, and standard error of measurement.ResultsGood-to-excellent intra-session reliability was found for all parameters and tasks (ICC: 0.79-0.99), whereas inter-session reliability varied across tasks. Static tasks demonstrated higher reliability in most parameters compared to functional and dynamic tasks. Absolute RMS and MNF showed the highest overall reliability across tasks (ICC: 0.66-0.98), while reliability of the barycentre was influenced by the direction of the movements.ConclusionRMS and MNF derived from HDEMG show consistent inter-session reliability in goal-directed voluntary movements of the trunk and reaching tasks, whereas the measures of the barycentre and entropy demonstrate task-dependent reliability.     

A submaximal test to assess back muscle capacity: Evaluation of construct validity

A functional endurance test more specific to common occupational tasks is proposed for assessing back muscle capacity. The test involves static intermittent contractions (8-s work-rest cycles) using a predefined absolute load (90 Nm) across subjects. Since the test involved an absolute endurance task, it was hypothesized that performance would be influenced by both the strength and relative endurance of the subjects, thus demonstrating the construct validity of this new test. Fifteen males and 17 females were assessed on three different days to allow familiarization and to measure their Strength as well as their absolute and relative endurance. Absolute and relative endurance were defined as the time to reach exhaustion (Tend_abs and Tend_rel, respectively) during a fatigue protocol including both an absolute (90 Nm) and a relative (40% of individual strength) load (extension moment at the L5/S1 joint). Strength and Tend_rel each explained an almost equivalent portion of Tend_abs (total variance explained: 61.5%), thus confirming the construct validity of the functional endurance test. This new test should better identify the back muscle impairments (weakness, fatigability) often observed in chronic low-back-pain patients.     

Unexpected Dual Task Benefits on Cycling in Parkinson Disease and Healthy Adults: A Neuro-Behavioral Model

BackgroundWhen performing two tasks at once, a dual task, performance on one or both tasks typically suffers. People with Parkinson’s disease (PD) usually experience larger dual task decrements on motor tasks than healthy older adults (HOA). Our objective was to investigate the decrements in cycling caused by performing cognitive tasks with a range of difficulty in people with PD and HOAs.MethodsTwenty-eight participants with Parkinson’s disease and 20 healthy older adults completed a baseline cycling task with no secondary tasks and then completed dual task cycling while performing 12 tasks from six cognitive domains representing a wide range of difficulty.ResultsCycling was faster during dual task conditions than at baseline, and was significantly faster for six tasks (all p<.02) across both groups. Cycling speed improved the most during the easiest cognitive tasks, and cognitive performance was largely unaffected. Cycling improvement was predicted by task difficulty (p<.001). People with Parkinson’s disease cycled slower (p<.03) and showed reduced dual task benefits (p<.01) than healthy older adults.ConclusionsUnexpectedly, participants’ motor performance improved during cognitive dual tasks, which cannot be explained in current models of dual task performance. To account for these findings, we propose a model integrating dual task and acute exercise approaches which posits that cognitive arousal during dual tasks increases resources to facilitate motor and cognitive performance, which is subsequently modulated by motor and cognitive task difficulty. This model can explain both the improvement observed on dual tasks in the current study and more typical dual task findings in other studies.     

Validation of a personalized curved muscle model of the lumbar spine during complex dynamic exertions

Previous curved muscle models have typically examined their robustness only under simple, single-plane static exertions. In addition, the empirical validation of curved muscle models through an entire lumbar spine has not been fully realized. The objective of this study was to empirically validate a personalized biologically-assisted curved muscle model during complex dynamic exertions. Twelve subjects performed a variety of complex lifting tasks as a function of load weight, load origin, and load height. Both a personalized curved muscle model as well as a straight-line muscle model were used to evaluate the model’s fidelity and prediction of three-dimensional spine tissue loads under different lifting conditions. The curved muscle model showed better model performance and different spinal loading patterns through an entire lumbar spine compared to the straight-line muscle model. The curved muscle model generally showed good fidelity regardless of lifting condition. The majority of the 600 lifting tasks resulted in a coefficient of determination (R²) greater than 0.8 with an average of 0.83, and the average absolute error less than 15% between measured and predicted dynamic spinal moments. As expected, increased load and asymmetry were generally found to significantly increase spinal loads, demonstrating the ability of the model to differentiate between experimental conditions. A curved muscle model would be useful to estimate precise spine tissue loads under realistic circumstances. This precise assessment tool could aid in understanding biomechanical causal pathways for low back pain.