Contents lists available at ScienceDirect Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo Effects of standing on typing task performance and upper limb discomfort, vascular and muscular indicators Larissa M. Fedorowich a,b , Julie N. Côté a,b,* a Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec, H2W 1S4, Canada b Feil & Oberfeld/CRIR Research Center, Jewish Rehabilitation Hospital, 3205 Alton, Goldbloom Place, Laval, Quebec, H7V 1R2, Canada ARTICLE INFO Keywords: Computer work Standing Neck/shoulder ABSTRACT Standing is a popular alternative to traditionally seated computer work. However, no studies have described how standing impacts both upper body muscular and vascular outcomes during a computer typing task. Twenty healthy adults completed two 90-min simulated work sessions, seated or standing. Upper limb discomfort, electromyography (EMG) from eight upper body muscles, typing performance and neck/shoulder and forearm blood flow were collected. Results showed significantly less upper body discomfort and higher typing speed during standing. Lower Trapezius EMG amplitude was higher during standing, but this postural difference de- creased with time (interaction effect), and its variability was 68% higher during standing compared to sitting. There were no effects on blood flow. Results suggest that standing computer work may engage shoulder girdle stabilizers while reducing discomfort and improving performance. Studies are needed to identify how standing affects more complex computer tasks over longer work bouts in symptomatic workers. 1. Introduction Many studies have suggested that the sitting posture provokes musculoskeletal discomfort during computer work (Husemann et al., 2009; Fedorowich et al., 2015; Juul-Kristensen and Jensen, 2005). However, in recent years, standing computer work has become a pop- ular alternative. A study suggested that the standing posture may pro- mote cognitive performance through stimulation of the cardiovascular system, promoting greater awareness compared to sitting (Caldwell et al., 2003). Moreover, studies have found no detrimental effect of sit/ stand alternations on computer work performance, although the sit/ stand condition has shown increased physical and psychological well- being compared to sitting (Husemann et al., 2009; Ebara et al., 2008), suggesting some relevant benefits to workplace health. Despite some potentially positive effects of the standing computer work posture, some studies comparing postural discomfort during computer tasks have shown higher overall comfort while sitting and greater fatigue and discomfort in standing after 20 min (Beers et al., 2008), 45 min (Lin et al., 2017) and after 90 min (Chester et al., 2002). Recently, another study on prolonged standing during computer work showed that multisite discomfort (lower limb, lower back and upper limb) increased after 120 min (Baker et al., 2018). Moreover, in a study focusing on the neck/shoulder region, discomfort was reported after 18 min in the seated posture but after 72 min while walking on a treadmill (Fedorowich et al., 2015). Furthermore, a six-week study with height adjustable tables found less upper body discomfort and muscu- loskeletal disorder (MSD) symptoms when participants could freely alternate table height (Hedge and Ray, 2004). These studies suggest benefits of other computer work postures, at least on subjective symptoms of discomfort. Some recent studies have investigated the effects of standing work (in comparison to sitting) on upper trunk and limb tridimensional posture, electromyography (EMG) and discomfort, an approach that may help to explain mechanisms underlying discomfort in different working postures. Lin et al. (2017) showed that standing computer workstation reduced non-neutral shoulder posture and associated EMG but increased those of the wrist. However, Botter et al. (Botter et al. (2016) showed that the upper trapezius EMG amplitude was only marginally changed when computer work was accomplished in sitting, standing, and dynamic postures. High EMG amplitude during computer tasks may pose a risk for development of MSDs with increases over time (Kleine et al., 1999) or sustained activity levels thought to pose an in- jury risk (Westgaard et al., 2001), although there is little empirical evidence to support this (Strom et al., 2009b). Another motor pattern inferred from muscle activity signals is motor variability, defined as the variation of behavioral outcomes over repetitions or time (Latash et al., 2002). Research shows a lack of motor variability, in occupations re- quiring prolonged low-level muscle activity, as a risk factor for https://doi.org/10.1016/j.apergo.2018.05.009 Received 10 September 2017; Received in revised form 2 April 2018; Accepted 17 May 2018 * Corresponding author. Department of Kinesiology and Physical Education, McGill University, Currie Gym office A218 475 Pine Avenue West, Montreal, QC, H2W 1S4, Canada. E-mail address: julie.cote2@mcgill.ca (J.N. Côté). Applied Ergonomics 72 (2018) 121–127 0003-6870/ © 2018 Elsevier Ltd. All rights reserved. T