Improving Trip- and Slip-Resisting Skills in Older People: Perturbation Dose Matters

Aging negatively affects balance recovery responses after trips and slips. We hypothesize that older people can benefit from brief treadmill-based trip and slip perturbation exposure despite reduced muscular capacities, but with neuropathology, their responsiveness to these perturbations will be decreased. Thus, to facilitate long-term benefits and their generalizability to everyday life, one needs to consider the individual threshold for perturbation dose. This is a non-final version of an article published in final form in Exercise and Sport Sciences Review

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4: II. 2H and 7Li NMR stimulated-echo experiment

We use 2H NMR stimulated-echo spectroscopy to measure two-time correlation functions characterizing the polymer segmental motion in polymer electrolytes PPO-LiClO4 near the glass transition temperature Tg. To investigate effects of the salt on the polymer dynamics, we compare results for different ether oxygen to lithium ratios, namely, 6:1, 15:1, 30:1 and infinity. For all compositions, we find nonexponential correlation functions, which can be described by a Kohlrausch function. The mean correlation times show quantitatively that an increase of the salt concentration results in a strong slowing down of the segmental motion. Consistently, for the high 6:1 salt concentration, a high apparent activation energy E_a=4.1eV characterizes the temperature dependence of the mean correlation times at Tg < T< 1.1T_g, while smaller values E_a=2.5eV are observed for moderate salt contents. The correlation functions are most nonexponential for 15:1 PPO-LiClO4, whereas the stretching is reduced for higher and lower salt concentrations. A similar dependence of the correlation functions on the evolution time in the presence and in the absence of ions indicates that addition of salt hardly affects the reorientational mechanism. For all compositions, mean jump angles of about 15 degree characterize the segmental reorientation. In addition, comparison of results from 2H and 7Li NMR stimulated-echo experiments suggests a coupling of ion and polymer dynamics in 15:1 PPO-LiClO4.Comment: 14 pages, 12 figure

Retention of gait stability improvements over 1.5 years in older adults:effects of perturbation exposure and triceps surae neuromuscular exercise

The plantarflexors play a crucial role in recovery from sudden disturbances to gait. The objective of this study was to investigate whether medium (months)- or long(years)-term exercise-induced enhancement of triceps surae (TS) neuromuscular capacities affects older adults' ability to retain improvements in reactive gait stability during perturbed walking acquired from perturbation training sessions. Thirty-four adult women (65 +/- 7 yr) were recruited to a perturbation training group (n = 13) or a group that additionally completed 14 wk of TS neuromuscular exercise (n = 21), 12 of whom continued with the exercise for 1.5 yr. The margin of stability (MoS) was analyzed at touchdown of the perturbed step and the first recovery step following eight separate unexpected trip perturbations during treadmill walking. TS muscle-tendon unit mechanical properties and motor skill performance were assessed with ultrasonography and dynamometry. Two perturbation training sessions (baseline and after 14 wk) caused an improvement in the reactive gait stability to the perturbations (increased MoS) in both groups. The perturbation training group retained the reactive gait stability improvements acquired over 14 wk and over 1.5 yr. with a minor decay over time. Despite the improvements in TS capacities in the additional exercise group. no benefits for the reactive gait stability following perturbations were identified. Therefore, older adults' neuromotor system shows rapid plasticity to repeated unexpected perturbations and an ability to retain these adaptations in reactive gait stability over a long time period, but an additional exercise-related enhancement of TS capacities seems not to further improve these effects. NEW & NOTEWORTHY Older adults' neuromotor system shows rapid plasticity to repeated exposure to unexpected perturbations to gait and an ability to retain the majority of these adaptations in reactive recovery responses over a prolonged time period of 1.5 yr. However, an additional exercise-related enhancement of TS neuromuscular capacities is not necessarily transferred to the recovery behavior during unexpected perturbations to gait in older adults

B595: An Illustrated Review of Apple Virus Diseases

The writers have attempted to review the available literature on the subject and to organize it in an orderly fashion. The name, symptomatology, host range, and geographic distribution are given for each virus disease. Where it was possible illustrations of each disorder have also been included. This bulletin addresses the following apple virus diseases: apple mosaic, flat limb, rubbery wood, stem pitting, spy 227 apple reaction, dwarf fruit and decline, chat fruit, chlorotic leaf spot, leaf pucker, dapple apple, false sting and green crinkle, green mottle, ring spot, star cracking, scar skin, rough skin, apple proliferation, rosettehttps://digitalcommons.library.umaine.edu/aes_bulletin/1068/thumbnail.jp

History Memorized and Recalled upon Glass Transition

The memory effect upon glassification is studied in the glass to rubber transition of vulcanized rubber with the strain as a controlling parameter. A phenomenological model is proposed taking the history of the temperature and the strain into account, by which the experimental results are interpreted. The data and the model demonstrate that the glassy state memorizes the time-course of strain upon glassification, not as a single parameter but as the history itself. The data also show that the effect of irreversible deformation in the glassy state is beyond the scope of the present model. Authors' remark: The title of the paper in the accepted version is above. The title appeared in PRL is the one changed by a Senior Assistant Editor after acceptance of the paper. The recovery of the title was rejected in the correction process.Comment: 4 pages, 4 figure

Aspects of topology of condensates and knotted solitons in condensed matter systems

The knotted solitons introduced by Faddeev and Niemi is presently a subject of great interest in particle and mathematical physics. In this paper we give a condensed matter interpretation of the recent results of Faddeev and Niemi.Comment: v2: Added a reference to the paper E. Babaev, L.D. Faddeev and A.J. Niemi cond-mat/0106152 where an exact equivalence was shown between the two-condensate Ginzburg-Landau model and a version of Faddeev model. Miscelaneous links related to knotted solitons are available at the author homepage at http://www.teorfys.uu.se/PEOPLE/egor/ . Animations of knotted solitons by Hietarinta and Salo are available at http://users.utu.fi/h/hietarin/knots/c45_p2.mp

Perturbation-based balance training: Principles, mechanisms and implementation in clinical practice

Since the mid-2000s, perturbation-based balance training has been gaining interest as an efficient and effective way to prevent falls in older adults. It has been suggested that this task-specific training approach may present a paradigm shift in fall prevention. In this review, we discuss key concepts and common issues and questions regarding perturbation-based balance training. In doing so, we aim to provide a comprehensive synthesis of the current evidence on the mechanisms, feasibility and efficacy of perturbation-based balance training for researchers and practitioners. We address this in two sections: “Principles and Mechanisms” and “Implementation in Practice.” In the first section, definitions, task-specificity, adaptation and retention mechanisms and the dose-response relationship are discussed. In the second section, issues related to safety, anxiety, evidence in clinical populations (e.g., Parkinson's disease, stroke), technology and training devices are discussed. Perturbation-based balance training is a promising approach to fall prevention. However, several fundamental and applied aspects of the approach need to be further investigated before it can be widely implemented in clinical practice

Extracting spectral density function of a binary composite without a-priori assumption

The spectral representation separates the contributions of geometrical arrangement (topology) and intrinsic constituent properties in a composite. The aim of paper is to present a numerical algorithm based on the Monte Carlo integration and contrainted-least-squares methods to resolve the spectral density function for a given system. The numerical method is verified by comparing the results with those of Maxwell-Garnett effective permittivity expression. Later, it is applied to a well-studied rock-and-brine system to instruct its utility. The presented method yields significant microstructural information in improving our understanding how microstructure influences the macroscopic behaviour of composites without any intricate mathematics.Comment: 4 pages, 5 figures and 1 tabl

Muscle-tendon adaptation monitoring in elite athletes: Preliminary results from a longitudinal investigation

In this study, we analysed the triceps surae(TS) muscle-tendon unit (MTU) mechanical properties (muscle strength and tendon stiffness) in elite jumping event athletes (long jump, triple jump, high jump, pole vault) and monitored the training-induced alterations in these properties over one year in nine elite jumpers, in order to detect potential changes in the uniformity of adaptation within the TS MTU.The findings indicate to a higher TS muscle strength and Achilles tendon stiffness in the take-off leg in comparison to the swing leg. The longitudinal monitoring revealed a concordant muscle and tendon adaptation in the TS MTU in both legs in the selected athletes

Monitoring muscle-tendon adaptation in elite athletes: Preliminary data from a 1-year longitudinal investigation

Introduction Muscles and tendons adapt to mechanical loading (Arampatzis et al., 2007). However, different time courses of adaptation in response to training (Mersmann et al., 2016) may lead to discordance within the muscle-tendon unit (MTU), potentially increasing the risk of injury. In this study, we monitored the triceps surae (TS) MTU mechanical properties in elite jumpers over one year of training and competing, in order to detect potential training-induced discordance between muscle and tendon adaptation. Methods This preliminary analysis is part of an ongoing nationwide study on the TS MTU adaptation of more than 30 jumpers (long jump, triple jump, high jump and pole vault) of the German national team. Maximum ankle plantarflexion moment and Achilles tendon (AT) stiffness of nine jumpers (23±3y) and one jumper 10 months post Achilles tendon reconstruction, were regularly assessed over 1 year at their respective Olympic training centres, using a mobile device (dynamometry and ultrasonography; TEMULAB®, Protendon, Aachen, Germany). Both time course and coefficients of variation (CV) of muscle and tendon adaptation were evaluated. Results On average, 16 measurements were conducted for these first 10 athletes. Both TS muscle strength and AT stiffness were higher in the take-off leg (average: 371±58Nm and 874±113N/mm, respectively) compared to swing leg (348±44Nm/kg; 812±110N/mm). In both legs, the relative changes of TS muscle strength and AT stiffness over one year showed similar patterns, meaning that changes in TS muscle strength were followed by changes in AT stiffness, with CVs of 8.9±2% and 12.9±4.9% respectively. However, following AT reconstruction, TS muscle strength but not AT stiffness was consistently lower in the affected leg (average over all data points: 1.8±0.2Nm/kg; 503.7±90.7N/mm) compared to the healthy leg (3.4±0.2Nm/kg; 496.8±33.1N/mm), despite intensive training. Discussion Our results indicate limb-specific differences of both TS muscle strength and AT stiffness due to training, with higher values for the take-off leg compared to the swing leg. Over one year there was a concordant adaptation of TS muscle strength and AT stiffness in both legs, suggesting a low tendon injury risk due to discordance within TS MTU. Following AT reconstruction, a consistent deficit in TS muscle strength but not AT stiffness was seen compared to the healthy leg, meaning that AT rupture and reconstruction could be risk factors for irreversible discordance within TS MTU. References Arampatzis et al. (2007). J Exp Biol, 210, 2743-2753. Mersmann et al. (2016). J Appl Physiol, 121, 893-899