The force-driven harmonic oscillator model for energy-efficient locomotion in individuals with transtibial amputation

The force-driven harmonic oscillator (FDHO) model states that the driving force is minimum at the resonant period of an oscillator. By manipulating prosthetic mass, this study explored the compromise of resonant periods between the two legs in persons with unilateral traumatic transtibial amputation (TTA) at self-selected walking velocity (SSWV), with an aim to better understand the energy minimization mechanisms of walking. It was hypothesized that (1) SSWV was the most energy-efficient walking velocity (MEWV), (2) the stride period at SSWV (Ts) is a compromise between the resonant periods of the normal leg (Tn) and the prosthetic leg (Tp) when they are dissimilar. Eight subjects completed multiple-speed treadmill walking tests (at 53, 67, 80, 93, and 107 m/min) according to three mass conditions (60%, 80%, and 100% of the normal leg below-knee mass) in a random order. Oxygen consumption and stride period were measured, and SSWV was empirically determined. The MEWV, the speed with minimum energy expenditure per distance traveled, was derived from quadratic regression, and its stride period (Tm) was estimated. A theoretical compromise period (Tv) between Tn and Tp was predicted by a virtual single pendulum system based on Huygens' Law. Across different mass conditions, comparisons were made among: Ts, Tm, Tv, Tn, and Tp. Results showed that: (1) Ts was significantly different from Tm; (2) Ts was greater than both Tn and Tp; (3) no significant difference was found between Tm and Tn. Implications for amputee rehabilitation in terms of thigh muscle training and prosthesis development were discussed.     

Joint consideration of energy expenditure,air quality,and safety by cyclists

Public health benefits are an important motivator and justification for urban cycling promotion. The health impacts of cycling are typically evaluated using three main effect pathways: physical activity (exercise), air pollution exposure, and safety (crashes). Effects of safety on cycling behaviour have been investigated, but little is known about how energy expenditure and air quality concerns influence cycling decisions. Understanding cyclist perceptions and preferences is important for planning and designing sustainable and healthy transportation networks. As such, research providing insights into the heterogeneity of these concerns is needed to inform models of behavioural change with evolving vehicles, technology, and infrastructure. The objective of this paper is to investigate the joint consideration of energy expenditure, air quality, and safety concerns by cyclists, and their relationships with cycling frequency. A structural equation model is developed based on data from a survey of 625 intercepted real-world cyclists. Air quality and energy expenditure were considered in routing decisions by 51% and 73% of the cyclists, respectively. Model results show that traffic safety and air pollution risks are perceived differently by cyclists, which has implications for modeling urban cycling behaviour in the context of evolving motor vehicle fleets. Safety concerns were associated with less frequent cycling, but not air quality concerns. Consideration of energy expenditure varies significantly among individuals and trip types, which will emerge with different preferences related to hills, stops, speeds, and electric-assistance. Energy and air quality concerns were significantly associated, suggesting health-conscious cyclists who tended to be older, have higher educational attainment, be more physically active, and cycle more recreationally. Utilitarian and recreational cycling trips had different relationships with health-related considerations and with weekly physical activity.     

The use of the large-scale integrated sensor (LSI) to estimate energy expenditure

The relationship between activity counts from the large-scale integrated sensor (LSI), placed at the hip and ankle, and heart rate-estimated energy expenditure was examined in three nonobese males during three conditions: normal morning activities, a 1-mi walk, and a 2-mi walk. Results showed that estimated caloric expenditure was related to activity counts for both monitoring placements, with correlations between counts and energy expenditure exceedingr=.90. These results show that energy expenditure in the activities sampled can be reliably estimated using activity monitors.This research was supported in part by a grant provided by The John D. and Catherine T. MacArthur Foundation Research Network on the Psychobiology of Depression, Clinical Research Center Grant 5-30915 from the NIMH, and Grant HD 16411 from the NICHD awarded to Dr. Epstein.     

When Sharing Is Not Caring: Does (un)Certainty About Bill Payment Method Lead Diners to Consume More and Spend More Money?

Previous work has demonstrated that unacquainted participants in an experimental, restaurant‐like setting consume more when they know in advance that the bill will be split evenly rather than paid according to individual consumption. Real life, however, often differs from these experimental settings in two important ways. First, unlike random groups of participants, diners who eat together are frequently friends or colleagues. Second, payment method (even vs. individual payment) is usually unknown (i.e. uncertain) at the time people place their orders, and is determined when the check arrives. The current research tests the ecological validity of the association between consumption amount and payment method. Study 1 was conducted in a natural setting with organic groups of diners. Some were asked to state their desired payment method before ordering (Certain condition); others did so only after asking for the check (Uncertain condition). In both conditions, even payment (as opposed to individual payment) was associated with greater consumption amount. However, overall, consumption amount was lower among diners in the Uncertain condition than among those in the Certain condition. Study 2 presents a controlled follow‐up experiment showing that eliminating diners' prior expectations regarding the payment method—by informing them that the payment method will be randomly determined after the consumption decision—eliminates the relationship between payment method and consumption amount. This study further indicates that when diners are uncertain what the payment method will be, even bill‐splitting has negative implications for their subsequent social interactions, expressed in retribution tendencies. Copyright © 2016 John Wiley & Sons, Ltd.     

美国医疗保险为什么"抛弃"在职者

美国医疗保险领域存在一个令人费解的现象:老年人、儿童有着相对完善的医疗保险体系,而最具生产能力的在职者却成为公共医疗保险(社会医疗保险)的"弃儿",大量在职人口医疗保险制度的缺乏,对美国社会经济造成了显著负面影响,并开始引起人们的关注.在分析美国不同年龄段人口医疗保险制度现状的基础上,从美国公共医疗保险制度设计、雇主医疗保险制度特点等角度分析美国在职者无医疗保险现象产生的原因及其影响,并探讨美国医疗保险未来的发展走向.     

Pendular energy transduction in the different phases of gait cycle in post-stroke subjects

MainTo analyze spatiotemporal gait parameters and the body center of mass (CoM) energy transduction at self-selected speed walking in a group of older patients with stroke.MethodsA cross-sectional study, fifteen subjects with 4.06 years post ̵stroke hemiparesis (eleven men and four women) and fifteen healthy subjects (four men and eleven women) participate in this study. Pendulum-like determining variables; Recovery (R) and Congruity percentage (%Cong) were analyzed in addition to immediate pendular re-conversion (Rint) during the phases in which the gait cycle is usually divided in clinical evaluations.ResultsHealthy subjects walked faster that stroke group (p = 0.001). %Cong was significantly higher in post-stroke respect to healthy subjects (p = 0.05). Rint showed significant differences between the groups for all phases (p = 0.05). The relation between speed and R was confirmed, for healthy (r = 0.67, p = 0.006) and post-stroke subjects (r = 0.851, p = 0.001), %Cong y Rint (r = −0.79, p = 0.001), (r = −0.93, p = 0.001) and periods of double support (r = −0.76, p = 0.001), (r = 0.69, p = 0.004) respectively.ConclusionAlteration of pendular mechanism in subjects post-stroke is associated mainly with energy transduction; mechanical energy recovered during double support phases in healthy and post-stroke subjects follows a different trend, in post-stroke subjects, a longer duration of the double support is associated with less energy loss.