We tested the hypotheses that: (1) anxiety regarding the possibility of falling alters the attentional demands of gait; and (2) this alteration in the attentional requirements of gait occurs independently of gait pattern accommodations. Sixteen younger and 15 older adults participated in this study. Subjects walked at a self-determined velocity along a 7.2-m walkway under four conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (60 cm vs 15 cm) and the height of the walking surface (0 cm vs 60 cm). Attentional demands of locomotion in each condition of testing were assessed using the dual-task methodology, in which participants verbally responded to an auditory cue as quickly as possible while continuing to walk. Our findings revealed that: (1) participants were successful in verbally responding to the auditory cue without modifying their gait pattern; (2) reaction times increased for all subjects when walking in the condition of greatest postural threat; (3) the attentional demands for locomotion varied with the phase of the gait cycle for younger adults but not for older adults; (4) the phase-dependent effect for younger adults disappeared in the condition of greatest postural threat, while reaction time scores for older adults systematically increased; and (5) increases in reaction time persisted despite significant changes in gait kinematics. Our findings confirm that anxiety increases the attentional demands for locomotion and provide further explanation for age-dependent increases in the attentional demands of gait. Furthermore, our findings confirm that fall-related anxiety predicates an increase in the allocation of attention to locomotor control that is independent of gait pattern adjustments.

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Background. The purpose of this study was to determine if the prioritization of postural control over secondary task performance is altered in younger and older adults under different conditions of postural threat. Methods. Fifteen healthy older adults (mean age = 69.53 +/- 5.78) and 15 younger adults (mean age = 22.00 +/- 2.17) performed Brooks' Spatial Letter Task (BST) while standing in four conditions of postural threat. Galvanic skin conductance (GSC) was collected to measure changes in physiological arousal. BST task duration was used to measure changes in cognitive performance, and center of pressure (COP) area was used to determine changes in postural stability across each of the testing conditions. A prioritization index was calculated based on the relative change in BST and COP across testing conditions. This measure was used to quantify changes in the relationship between postural control and secondary task performance under conditions of postural threat. Results. Measures of GSC increased in younger and older adults in response to conditions of increased postural threat. Prioritization index scores revealed that a greater number of older adults than younger adults prioritized postural control over secondary task performance under conditions of increased postural threat. Conclusions. Environmental contexts that alter postural threat may lead to modifications in the prioritization between postural control and secondary task performance among older adults. This relationship may have implications for postural control under situations that do not afford deterioration in secondary task performance.

We tested the hypothesis that anxiety regarding the potential consequences of a possible fall would alter gait patterns differently between younger and older adults. Sixteen younger and fifteen older adults participated in this study. Participants walked at a self-determined velocity along a 7.2-m walkway under 4 different conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (0.60 m vs 0.15 m) and the height of the walking surface (floor vs elevated: 0 m vs 0.60 m). Results indicated that although both younger and older adults altered their gait patterns under conditions of increased postural threat, the movement adaptations observed among older adults were substantially different to those adopted by younger adults. These age-dependent differences were strongly evidenced in the joint kinematics and the variability of the gait pattern within each condition. Our findings also indicated that when postural threat increased, the level of muscle activation throughout the gait cycle was altered in the distal musculature (gastrocnemius m. and tibialis anterior m.) among older adults only. Based on the age-related differences observed, we believe that the gait pattern alterations observed among younger and older adults reflect central set modifications to postural control that are mediated by a heightened anxiety imposed by the constraints of the testing conditions. Based on the age-dependent differences in the observed gait pattern modifications, it appears that the effects of anxiety on the control of locomotion are more pervasive for older adults than for younger adults.

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The short- and long-latency (SLSR, LLSR) components of the stretch reflex response were investigated in the forearm using a paired transcranial magnetic stimulation (TMS)-stretch reflex protocol. Responses to TMS were recorded in the flexor and extensor carpi radialis muscles (FCR, ECR) after conditioning with a rapid wrist extension movement. The cortical stimuli were timed to elicit a motor-evoked potential (MEP) at either the SLSR or LLSR onset in the FCR muscle. Responses were also collected in TMS-alone and stretch reflex-alone conditions. Six intensities of magnetic stimulation were applied in all conditions. In the FCR muscle, MEP amplitude when timed to arrive at the LLSR onset was significantly greater than the sum of the MEP and stretch reflex responses when given separately. MEP amplitudes at the SLSR onset in the FCR muscle and in the ECR muscle at both SLSR and LLSR onset were not significantly different from that expected from the sum of the two stimuli given separately. This indicates heightened corticospinal excitability at a time corresponding to the passage of an afferent volley induced by the stretch, and raises the possibility of a transcortical loop of the LLSR in the forearm. The extent of MEP facilitation was generally consistent across all stimulus intensities tested. A reduced component of the LLSR was evident when the stretch response was timed to arrive during the silent period following the cortical stimulus, suggesting both cortical and sub-cortical components to the reflex response.

This article analyzes the international relations of Ukraine during the national liberation struggle of 1917-1918. The prerequisites for the intensification of Ukrainian-German contacts at the end of the First World War are studied. The peculiarities of contacts between Germany and Ukrainian governments are analyzed, the significant influence of German policy in the context of the formation and development of Ukrainian state-building processes is indicated. The participation of the Ukrainian delegation at the Brest-Litovsk negotiations and the conclusion of a peace treaty with the Central Powers are characterized. The methodology is based on the principle of historicism and scientificity. The method of comparative analysis, retrospective, historical-typological, was used. Scientific novely. The article examines the economic and political components in the system of Ukrainian-German bilateral relations, which significantly influenced the structure of the foreign policy course of the official UNR and Germany, and also became the basis for the conclusion of international agreements. The active work of Ukrainian diplomacy and trade and economic missions abroad was studied, which was aimed at ensuring the development of the Ukrainian economy and the needs of the war for independencе. Conclusions. It has been proven that the signing of the Brest-Litovsk Treaty, which certified the international recognition of the state of the Ukrainian People’s Republic, can be called a significant result of the formation of interstate Ukrainian-German relations. It is shown that Ukrainian-German relations influenced further interstate military-political and diplomatic relations. The most important achievement of Ukraine at that time was the preservation of state independence, which made it possible to continue national liberation struggles in the future. In general, conducting such a study is appropriate not only in the context of the history of Germany and Ukraine, but also in the context of world history, since the evolution of Ukrainian-German relations during this period largely depended on the development of events in the international arena.