The reliability of side to side measurements of upper extremity activity levels in healthy subjects

<p>Abstract</p> <p>Background</p> <p>In both clinical and occupational settings, ambulatory sensors are becoming common for assessing all day measurements of arm motion. In order for the motion of a healthy, contralateral side to be used as a control for the involved side, the inherent side to side differences in arm usage must be minimal. The goal of the present study was to determine the reliability of side to side measurements of upper extremity activity levels in healthy subjects.</p> <p>Methods</p> <p>Thirty two subjects with no upper extremity pathologies were studied. Each subject wore a triaxial accelerometer on both arms for three and a half hours. Motion was assessed using parameters previously reported in the literature. Side to side differences were compared with the intraclass correlation coefficient, standard error of the mean, minimal detectable change scores and a projected sample size analysis.</p> <p>Results</p> <p>The variables were ranked based on their percentage of minimal detectable change scores and sample sizes needed for paired t-tests. The order of these rankings was found to be identical and the top ranked parameters were activity counts per hour (MDC% = 9.5, n = 5), jerk time (MDC% = 15.8, n = 8) and percent time above 30 degrees (MDC% = 34.7, n = 9).</p> <p>Conclusions</p> <p>In general, the mean activity levels during daily activities were very similar between dominant and non-dominant arms. Specifically, activity counts per hour, jerk time, and percent time above 30 degrees were found to be the variables most likely to reveal significant difference or changes in both individuals and groups of subjects. The use of ambulatory measurements of upper extremity activity has very broad uses for occupational assessments, musculoskeletal injuries of the shoulder, elbow, wrist and hand as well as neurological pathologies.</p

Behaviour of motor unit action potential rate, estimated from surface EMG, as a measure of muscle activation level

BACKGROUND: Surface electromyography (EMG) parameters such as root-mean-square value (RMS) are commonly used to assess the muscle activation level that is imposed by the central nervous system (CNS). However, RMS is influenced not only by motor control aspects, but also by peripheral properties of the muscle and recording setup. To assess motor control separately, the number of motor unit action potentials (MUAPs) per second, or MUAP Rate (MR) is a potentially useful measure. MR is the sum of the firing rates of the contributing MUs and as such reflects the two parameters that the CNS uses for motor control: number of MUs and firing rate. MR can be estimated from multi-channel surface EMG recordings. The objective of this study was to explore the behaviour of estimated MR (eMR) in relation to number of active MUs and firing rate. Furthermore, the influence of parameters related to peripheral muscle properties and recording setup (number of fibers per MU, fiber diameter, thickness of the subcutaneous layer, signal-to-noise-ratio) on eMR was compared with their influence on RMS. METHODS: Physiological parameters were varied in a simulation model that generated multi-channel EMG signals. The behaviour of eMR in simulated conditions was compared with its behaviour in experimental conditions. Experimental data was obtained from the upper trapezius muscle during a shoulder elevation task (20–100 N). RESULTS: The simulations showed strong, monotonously increasing relations between eMR and number of active MUs and firing rate (r(2 )> 0.95). Because of unrecognized superimpositions of MUAPs, eMR was substantially lower than the actual MUAP Rate (aMR). The percentage of detected MUAPs decreased with aMR, but the relation between eMR and aMR was rather stable in all simulated conditions. In contrast to RMS, eMR was not affected by number of fibers per MU, fiber diameter and thickness of the subcutaneous layer. Experimental data showed a strong relation between eMR and force (individual second order polynomial regression: 0.96 < r(2 )< 0.99). CONCLUSION: Although the actual number of MUAPs in the signal cannot be accurately extracted with the present method, the stability of the relation between eMR and aMR and its independence of muscle properties make eMR a suitable parameter to assess the input from the CNS to the muscle at low contraction levels non-invasively

Cross-sectional associations between occupational factors and musculoskeletal pain in women teachers, nurses and sonographers

A. Technical measurements of the physical workload. (DOCX 18 kb

Perspectives on a ‘Sit Less, Move More’ Intervention in Australian Emergency Call Centres

Background: Prolonged sitting is associated with increased risk of chronic diseases. Workplace programs that aim to reduce sitting time (sit less) and increase physical activity (move more) have targeted desk-based workers in corporate and university settings with promising results. However, little is known about 'move more, sit less' programs for workers in other types of jobs and industries, such as shift workers. This formative research examines the perceptions of a 'sit less, move more' program in an Australian Emergency Call Centre that operates 24 hours per day, 7 days per week.  Methods: Participants were employees (N = 39, 72% female, 50% aged 36-55 years) recruited from Emergency Services control centres located in New South Wales, Australia. The 'sit less, move more' intervention, consisting of emails, posters and timer lights, was co-designed with the management team and tailored to the control centre environment and work practices, which already included electronic height-adjustable sit-stand workstations for all call centre staff. Participants reported their perceptions and experiences of the intervention in a self-report online questionnaire, and directly to the research team during regular site visits. Questionnaire topics included barriers and facilitators to standing while working, mental wellbeing, effects on work performance, and workplace satisfaction. Field notes and open-ended response data were analysed in an iterative process during and after data collection to identify the main themes.  Results: Whilst participants already had sit-stand workstations, use of the desks in the standing position varied and sometimes were contrary to expectations (e.g, less tired standing than sitting; standing when experiencing high call stress). Participants emphasised the "challenging" and "unrelenting" nature of their work. They reported sleep issues ("always tired"), work stress ("non-stop demands"), and feeling mentally and physically drained due to shift work and length of shifts. Overall, participants liked the initiative but acknowledged that their predominantly sitting habits were entrenched and work demands took precedence.  Conclusions: This study demonstrates the low acceptability of a 'sit less, move more' program in shift workers in high stress environments like emergency call centres. Work demands take priority and other health concerns, like poor sleep and high stress, may be more salient than the need to sit less and move more during work shifts

Multi-factor service design: identification and consideration of multiple factors of the service in its design process

Service design is a multidisciplinary area that helps innovate services by bringing new ideas to customers through a design-thinking approach. Services are affected by multiple factors, which should be considered in designing services. In this paper, we propose the multi-factor service design (MFSD) method, which helps consider the multi-factor nature of service in the service design process. The MFSD method has been developed through and used in five service design studies with industry and government. The method addresses the multi-factor nature of service for systematic service design by providing the following guidelines: (1) identify key factors that affect the customer value creation of the service in question (in short, value creation factors), (2) define the design space of the service based on the value creation factors, and (3) design services and represent them based on the factors. We provide real stories and examples from the five service design studies to illustrate the MFSD method and demonstrate its utility. This study will contribute to the design of modern complex services that are affected by varied factors

The contribution of office work to sedentary behaviour associated risk

Background: Sedentary time has been found to be independently associated with poor health and mortality. Further, a greater proportion of the workforce is now employed in low activity occupations such as office work. To date, there is no research that specifically examines the contribution of sedentary work to overall sedentary exposure and thus risk. The purpose of the study was to determine the total exposure and exposure pattern for sedentary time, light activity and moderate/vigorous physical activity (MVPA) of office workers during work and non-work time.Methods: 50 office workers from Perth, Australia wore an Actical (Phillips, Respironics) accelerometer during waking hours for 7 days (in 2008–2009). Participants recorded wear time, waking hours, work hours and daily activities in an activity diary. Time in activity levels (as percentage of wear time) during work and non-work time were analysed using paired t-tests and Pearson’s correlations.Results: Sedentary time accounted for 81.8% of work hours (light activity 15.3% and MVPA 2.9%), which was significantly greater than sedentary time during non-work time (68.9% p 30 minutes) and significantly less brief duration (0–10 minutes) light intensity activity during work hours compared to non-work time (p < 0.001). Further, office workers had fewer breaks in sedentary time during work hours compared to non-work time (p < 0.001).Conclusions: Office work is characterised by sustained sedentary time and contributes significantly to overall sedentary exposure of office workers