The effect of motivation on shoulder-muscle tension in attention-demanding tasks

This paper evaluates motivation as a task-related factor causing the development of psychologically mediated (‘psychogenic’) shoulder-muscle tension. In four separate experiments using a visual display unit (VDU) based complex reaction-time task, motivation was established by means of continuous feedback on the level of performance (relative to a preset target performance level) or by means of a money reward for good performance. In all experiments motivation improved the performance, but an increase in the psychogenic shoulder-muscle tension was only observed in the money-reward condition. It is discussed whether this difference in the muscle-tension response is due to changes in the subjects' attitude unrelated to performance or due to a superior performance in the money-reward condition.     

Shoulder load during machine milking An electromyographic and biomechanical study

Abstract

Ten professional milkers simulated 20 different machine-milking postures related to different vertical distances between milker and cow. The loading moment with respect to the shoulder joint bilateral axes was calculated, and EMGs from four shoulder muscles were recorded. The loading moments were related to isometric strength and EMG was standardized against an isometric maximum contraction. Muscle activity was low to moderate. Load moment increased with increasing level difference between milker and cow, but the simultaneous increase in strength utilization and muscular activation was lower than expected. About 25% of maximum shoulder flexor strength was required. The study illustrates some effects of the interaction between shoulder loading moment, trunk inclination and shoulder flexion. The method used gives load both in absolute form (loading moment) and in relation to individual capacity (strength utilization and normalized EMG).     

Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task

Data on exposure variability is an important remedy for designing and interpreting studies of occupational ergonomics. The present study aimed at retrieving the within- and between-subjects variance of several mechanical exposure parameters in a repeated, short-cycle task. Seven experienced operators repeatedly secured joints using two types of hand-held nutrunners. The joints were placed in three different locations on a rack, simulating automotive assembly. Bilateral muscle activity from the upper trapezius and the lower arm extensors, as well as head and upper arm inclination was continuously monitored. Exposure levels and their variance components were assessed in several data subsets using ANOVA. The results were interpreted in terms of statistical precision and power, and discussed as markers of important ergonomic qualities. A substantial exposure variability was found within and between subjects in all joint locations and for both tools. For mixed work across tools and locations, the necessary number of subjects to arrive at a group mean exposure with 95% confidence limits corresponding to ± 10% of the mean ranged between 8 and 158, with posture recordings tending to require smaller populations than muscle activity recordings. Within-subject variance increased 2- to 37-fold, depending on exposure parameter, when work was ‘enlarged’ from securings with a specified location and tool to a mix of all locations and tools. Systematic differences between subjects in variability and responsiveness to ‘work enlargement’ indicated individualized motor control strategies. The results illustrate the importance of exposure variability data to the design of proper measurement strategies. They also suggest that the sizes of exposure variability per se can be interpreted as operational indices of what is thought to be important ergonomic risk indicators, such as the ‘sameness’ of repeated operations and the allowance for flexible working techniques.     

Concurrent validation of magnetic and inertial measurement units in estimating upper body posture during gait

We assessed the concurrent validity of commercially available magnetic and inertial measurement units (MIMUs) for estimating mean postural angles for head flexion, thorax flexion and shoulder girdle elevation during gait in seven healthy individuals. Postural angles estimated with the MIMUs were compared with angles calculated using marker data from a gold standard motion capture system. Coefficients of determination of mean postural angles between measurement systems were 0.82 for head flexion, 0.58 for thorax flexion, and 0.77 for shoulder girdle elevation. Bland–Altman analysis showed good agreement between measurement systems. Intraclass correlation coefficients were 0.9 for head flexion, 0.73 for thorax flexion, and 0.87 for shoulder girdle elevation. Root mean square errors were less than 3° between measurement systems for all body segments. The present findings suggest that the MIMUs tested in this study are valid for estimating head flexion, thorax flexion and shoulder girdle elevation during gait.     

Alternative pre-rigor foreshank positioning can improve beef shoulder muscle tenderness

Thirty beef carcasses were harvested and the foreshank of each side was independently positioned (cranial, natural, parallel, or caudal) 1 h post-mortem to determine the effect of foreshank angle at rigor mortis on the sarcomere length and tenderness of six beef shoulder muscles. The infraspinatus (IS), pectoralis profundus (PP), serratus ventralis (SV), supraspinatus (SS), teres major (TM) and triceps brachii (TB) were excised 48 h post-mortem for Warner–Bratzler shear force (WBSF) and sarcomere length evaluations. All muscles except the SS had altered (P < 0.05) sarcomere lengths between positions; the cranial position resulted in the longest sarcomeres for the SV and TB muscles whilst the natural position had longer sarcomeres for the PP and TM muscles. The SV from the cranial position had lower (P < 0.05) shear than the caudal position and TB from the natural position had lower (P < 0.05) shear than the parallel or caudal positions. Sarcomere length was moderately correlated (r = − 0.63; P < 0.01) to shear force.     

浍河水库左坝肩渗漏及其工程方案选定

浍河水库左坝肩多次出现渗漏事故，在水库除险加固设计中，采用高喷防渗墙作为处理方案，文中对该方案的设计参数作了合理选定。     

激光穴照并穴位贴敷联合康复训练治疗脑卒中后肩手综合征的疗效观察

目的:观察激光穴照并穴位贴敷联合康复训练对脑卒中后肩手综合征的疗效影响。方法:将108例脑卒中后肩手综合征患者随机分为观察组和对照组,各54例。对照组采取康复训练;观察组在康复训练的基础上配合激光穴照并穴位贴敷治疗,治疗时间为4周。在治疗前后分别对两组采用目测类比评分法(VAS)、Barthel(BI)指数、改良的Fulg-Meyer(FMA)法评定患侧上肢手指水肿、疼痛程度、关节活动范围、日常生活活动能力(ADL)及上肢运动功能,评定其临床疗效。结果:两组治疗后偏瘫侧水肿、肩痛、关节活动度、Barthel指数及FMA-Meyer评分较治疗前均有显著改善(P0.05),观察组明显好于对照组(P0.05),且观察组临床疗效总有效率(96.30%)显著优于对照组(74.07%),P0.05。结论:激光穴照并穴位贴敷联合康复训练对脑卒中后肩手综合征疗效显著。     

三种不同镇痛方法对冻结肩松解术后康复影响的临床观察

目的:观察三种不同镇痛方法对冻结肩手法松解术后功能康复锻炼的影响。方法:将拟行手法松解治疗冻结肩的90例患者随机分为A、B、C三组。A组为肩关节腔内阻滞组,术后连续三天每天行单次肩关节腔内阻滞后进行功能康复锻炼。B组为臂丛阻滞麻醉组,术后连续三天每天行单次臂丛阻滞麻醉后进行功能康复锻炼。C组为对照组,术后不行任何阻滞下进行常规肩关节功能康复锻炼。观察松觧术当天、术后连续3天、术后1周的视觉模拟法评分、依从性、疗效评定及1月后的随访结果。结果:三组患者的疼痛、依从性、疗效评定比较,A组明显优于B组、C组(P0.05)。结论:肩关节腔内阻滞在手法松解治疗冻结肩后的康复锻炼中具有安全、痛苦小、易于患者接受、疗效确切的特点,该法值得推广。     

A review of: “Catastrophic Failures”. By V. BIGNELL,G. PETERS and C. PYM. (Milton Keynes: OPEN UNIVERSITY PRESS, 1977.) [Pp.274.] £5·50.

Cumulative trauma illness currently accounts for over half of all occupational illness in the United States. From 1987 to 1989 there was a 100% increase in the reported number of cases of cumulative trauma illness (Bureau of Labor Statistics 1990). Shoulder region pain ranks second only to low back and neck pain in clinical frequency, and the occurrence of occupational shoulder illness is on the rise. This paper summarizes findings of a subset of recent epidemiologic, laboratory, and field studies conducted in order to identify occupational risk factors for cumulative trauma disorders (CTDs) of the shoulder region. These studies have identified the following risk factors as being associated with particular shoulder pain syndromes: awkward or static postures, heavy work, direct load bearing, repetitive arm movements, working with hands above shoulder height, and lack of rest. The paper begins with a discussion of several shoulder disorders, includes problems in studying cumulative trauma, presents results of recent studies, and concludes with suggested ergonomic controls that could help to reduce the incidence of shoulder disorders, by eliminating or reducing exposure to the associated risk factors.