Tester and testing procedure influence clinically determined gait speed

BackgroundThere is a clinical need to be able to reliably detect meaningful changes (0.1 to 0.2 m/s) in usual gait speed (UGS) considering reduced gait speed is associated with morbidity and mortality.Research questionWhat is the impact of tester on UGS assessment, and the influence of test repetition (trial 1 vs. 2), timing method (manual stopwatch vs. automated timing), and starting condition (stationary vs. dynamic start) on the ability to detect changes in UGS and fast gait speed (FGS)?MethodsUGS and FGS was assessed in 725 participants on a 8-m course with infrared timing gates positioned at 0, 2, 4 and 6 m. Testing was performed by one of 13 testers trained by a single researcher. Time to walk 4-m from a stationary start (i.e. from 0-m to 4-m) was measured manually using a stopwatch and automatically via the timing gates at 0-m and 4-m. Time taken to walk 4-m with a dynamic start was measured during the same trial by recording the time to walk between the timing gates at 2-m and 6-m (i.e. after 2-m acceleration).ResultsTesters differed for UGS measured using manual vs. automated timing (p = 0.02), with five and two testers recording slower and faster UGS using manual timing, respectively. 95% limits of agreement for trial 1 vs. 2, manual vs. automated timing, and dynamic vs. stationary start ranged from ±0.15 m/s to ±0.20 m/s, coinciding with the range for a clinically meaningful change. Limits of agreement for FGS were larger ranging from ±0.26 m/s to ±0.35 m/s.SignificanceRepeat testing of UGS should performed by the same tester or using an automated timing method to control for tester effects. Test protocol should remain constant both between and within participants as protocol deviations may result in detection of an artificial clinically meaningful change.     

劳动姿势对流量－容积曲线的影响─—波速学说的进一步验证

用“点值法”对健康工人４７３例［轻体力劳动工人（简称轻工）２４８例，重体力劳动工人（简称重工）２２５例］。作了流量一容积曲线和常规通气功能检查。结果表明：重工男女在４０岁以后其高肺容积流量下降，３０岁以后低肺容积流量上升，而且这些改变有随年龄增长而更加明显的倾向；轻工仅有个别年龄组的低肺容积流量上升。对７名健康坐位工作者模拟劳动的前倾姿势作多次通气功能检查，亦有明显高肺容积流量下降和低肺容积流量上升的现象，这一事实提示波速学说亦可应用于颈和躯干前倾进行重体力劳动工人的通气行为。     

Editorial: Genetics of Brain Function and Cognition

There is overwhelming evidence for the existence of substantial genetic influences on individual differences in general and specific cognitive abilities, especially in adults. The actual localization and identification of genes underlying variation in cognitive abilities and intelligence has only just started, however. Successes are currently limited to neurological mutations with rather severe cognitive effects. The current approaches to trace genes responsible for variation in the normal ranges of cognitive ability consist of large scale linkage and association studies. These are hampered by the usual problems of low statistical power to detect quantitative trait loci (QTLs) of small effect. One strategy to boost the power of genomic searches is to employ endophenotypes of cognition derived from the booming field of cognitive neuroscienceThis special issue of Behavior Genetics reports on one of the first genome-wide association studies for general IQ. A second paper summarizes candidate genes for cognition, based on animal studies. A series of papers then introduces two additional levels of analysis in the black box between genes and cognitive ability: (1) behavioral measures of information-processing speed (inspection time, reaction time, rapid naming) and working memory capacity (performance on on single or dual tasks of verbal and spatio-visual working memory), and (2) electrophyiosological derived measures of brain function (e.g., event-related potentials). The obvious way to assess the reliability and validity of these endophenotypes and their usefulness in the search for cognitive ability genes is through the examination of their genetic architecture in twin family studies. Papers in this special issue show that much of the association between intelligence and speed-of-information processing/brain function is due to a common gene or set of genes, and thereby demonstrate the usefulness of considering these measures in gene-hunting studies for IQ.     

Contraction history affects the in vivo quadriceps torque-velocity relationship in humans

We hypothesized that the history of contraction would affect the in vivo quadriceps torque-velocity relationship. We examined the quadriceps torque-velocity relationship of the human knee extensors at the descending and ascending limb of the torque-position relationship by initiating the knee extension at a knee angle position of 1.39 rad (80°) or 0.87 rad (50°) over a 0.52 rad (30°) range of motion under conditions of constant or linearly increasing velocity. Maximal voluntary isometric knee extension torque (M₀) was measured at 1.87 rad, 0.87 rad, and 0.35 rad, and concentric torque was measured. The subjects carried out ten maximal knee extensions at ten distinct velocities, each velocity ranging between 0.52 rad·s^–1 to 5.24 rad·s^–1 in steps of 0.52 rad·s^–1. Peak concentric torque was measured and mean torque calculated from the respective torque-time curves. Peak or mean torque, computed from the individual torque-time curves, and velocity data were fitted to the Hill equation under the four experimental conditions and the curve parameters computed. The M₀ was similar at 0.87 rad and 1.39 rad, but it was significantly lower at 0.35 rad. In the low-velocity domain of the torque-velocity curve where a plateau normally occurs, peak torque was always lower than M₀. Peak and mean torque were significantly greater under linearly increasing velocity conditions and the 1.39 rad starting knee position. Mean torque but not peak torque data could be well fitted to the Hill equation and the two computations resulted in significantly different Hill curve parameters including the concavity ratio, peak power, and maximal angular velocity. We concluded that the history of contraction significantly modifies the in vivo torque-velocity relationship of the human quadriceps muscle. Muscle mechanics and not neural factors may have accounted for the inconsistencies in the human torque-velocity relationships reported previously. Electronic Publication     

工作记忆、执行功能、加工速度与数学障碍儿童推理和心算能力的关系

目的：探讨工作记忆、执行功能、加工速度与数学障碍儿童推理和心算能力的关系。方法：采用智力测验、成就测验、教师提名、学业成绩相结合的综合标准甑选数学障碍儿童，在长沙市三所小学随机选取4-6年级共12个班，从中抽取24名数学障碍儿壹和24名学习正常儿童。对两组儿童进行工作记忆、执行功能、加工速度以及数字推理、图案推理和心算测验。结果：数学障碍组的工作记忆、执行功能及加工速度测验成绩均屁著低于学习正常组（P〈0．001—0．05），数学障碍组数字推理、图案推理和心算成绩也湿著低于正常组；数字推理、图案推理及心算成绩与听觉工作记忆、视觉工作记忆、执行功能和加工速度均有显著相关；逐步回归分析结果显示，进入推理能力回归方程的自变量有听觉工作记忆和视觉工作记忆；进入心算的回归方程的是听觉工作记忆和加工速度。结论：数学障碍儿童存在工作记忆、执行功能和加工速度缺陷；数学障碍儿童的推理能力低于正常学习儿童，主要可由工作记忆能力不足来解释，而心算能力低下则可由听觉工作记忆和加工速度共同解释。     

Perceptual Speed and IQ Are Associated Through Common Genetic Factors

Individual differences in inspection time explain about 20% of IQ test variance. To determine whether the association between inspection time and IQ is mediated by common genes or by a common environmental factor, inspection time and IQ were assessed in an extended twin design. Data from 688 participants from 271 families were collected as part of a large ongoing project on the genetics of adult brain function and cognition. The sample consisted of a young adult cohort (mean age 26.2 years) and an older adult cohort (mean age 50.4 years). IQ was assessed with the Dutch version of the WAIS-3R. Inspection time was measured in the so-called -paradigm, in which a subject is asked to decide which leg of the -figure is longest at varying display times of the -figure. The number of correct inspections per second (i.e., the reciprocal of inspection time) was used to index perceptual speed. For Verbal IQ and Performance IQ, heritabilities were 85% and 69%, respectively. For perceptual speed, 46% of the total variance was explained by genetic variance. No differences in heritability estimates across age cohorts or sexes were found. Across the whole sample, a significant phenotypic correlation was found between perceptual speed and Verbal IQ (0.19) and between perceptual speed and Performance IQ (0.27). These correlations were entirely due to a common genetic factor that accounted for 10% of the genetic variance in verbal IQ and for 22% of the genetic variance in performance IQ. This factor is hypothesized to reflect the influence of genetic factors that determine axonal myelination in the central nervous system.     

Electrodermal Lability: Individual Differences Affecting Perceptual Speed and Vigilance Performance in 9 to 16 Year-Old Children

Studies on adults have suggested that a deterioration in performance (within session vigilance decrement) on a continuous performance task may be related to individual differences in baseline levels of electrodermal activity (electrodermal lability). This study investigated this relationship in 153 children, aged 9–16 years. A significant vigilance decrement was observed, as indicated by average decreases in perceptual sensitivity (d') over an 11.5-min time period. Although electrodermal labiles were overall more perceptually sensitive than electrodermal stabiles, results did not support the premise that the performance of stabiles decreases over time more than that of labiles. Performance on other cognitive tasks, involving tests of perceptual speed ability, did not appear to be highly related to vigilance performance. However labiles were not only better able to sustain their attention, but also performed better and faster on these cognitive tasks.     

Male mating speed as a component of fitness inDrosophila

From a survey of published data on the genusDrosophila, it is clear that male mating speed or male virility is probably the most important component of fitness. Rapid matings tend to be controlled by the male genotype, while the genotype of the female may assume importance for slower matings. Where data exist, male mating speed is subject to directional selection in the direction of rapid speed, as would be expected for an important component of fitness.Supported by the Australian Research Grants Committee.