Journal of Electromyography and Kinesiology 10 (2000) 301–312 www.elsevier.com/locate/jelekin Methodologies for evaluating electromyographic field data in ergonomics Go¨ran M. Ha¨gg a,* , Alwin Luttmann b , Matthias Ja¨ger b a Programme for Ergonomics, National Institute for Working Life, SE-112 79 Stockholm, Sweden b Institut fu¨ r Arbeitsphysiologie an der Universita¨t Dortmund, D-44139 Dortmund, Germany Abstract Surface electromyography (SEMG) is an important tool for work load assessment in ergonomics. Several different approaches using amplitude as well as frequency parameters give fruitful information depending on question at issue in the laboratory as well as in field studies. One basic factor determining the choice of analysis method is whether the SEMG is interpreted as an indicator of forces/torques or pure muscular activation. Two methods for occupational SEMG data reduction representing two different approaches to SEMG applications in ergonomics, Exposure Variation Analysis (EVA), and Joint Analysis of EMG Spectrum and Amplitude (JASA), applied on the same SEMG recording from three muscles during urology surgeon work, have been compared. The EVA method categorised the three muscle recordings as too static with no EMG gaps while the JASA method identifies fatigue in two of the three recordings. The practical relevance of these findings is discussed.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Electromyography; Dose; Exposure; Fatigue; Musculoskeletal disorders; Physical load 1. Introduction Prevention of various kinds of musculoskeletal dis- orders (MSD) is a cornerstone in ergonomics. Even if the mechanical load on the human body in working life is not the only causative factor, it is likely to constitute a major part of it. Hence estimation of the physical exposure (see below), and its physiological conse- quences, are essential activities in ergonomic work. Sur- face electromyography (SEMG) is one of the most important tools for doing this [33,54] and provides unique possibilities to get ‘on-line’ information, highly relevant from several ergonomic perspectives. The use of SEMG in ergonomics has a history of approximately 45 years. The Norwegian neurophysiolo- gist Lundervold was probably the first to use electromy- ography in a real work situation, i.e. typewriting [39]. Vocational electromyography has ever since been a strong discipline in the Nordic countries, however, the methodology is today applied in ergonomic investigations all over the world. In the European concerted action pro- * Corresponding author. Tel.: + 46-8-7309314; fax: + 46-8-7309246. E-mail address: goran.hagg@niwl.se (G.M. Ha¨gg). 1050-6411/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII:S1050-6411(00)00022-5 gram SENIAM (Surface Electromyography for Non- Invasive Assessment of Muscles [13]), applications in ergonomics were one of several focused themes. In this paper different methodological approaches are reviewed and two of the most elaborated methods, Exposure Vari- ation Analysis (EVA) [49] and Joint Analysis of EMG Spectrum and Amplitude (JASA) [44] are compared by analysis of the same SEMG raw data file. 2. Workload terminology The concept ‘exposure’ is well known from industrial hygiene and radiation biology describing the average exposure of a (harmful) agent or radiation. The dose is then easily calculated as the exposure times the duration. Modern ergonomics has adopted and further developed this terminology. External exposure refers to external mechanical circumstances related to the work task but independent of the operator while the internal exposure describes forces and torques acting on and inside the body of an operator [62]. The internal exposure may then cause various detrimental effects in different tissues. A considerable part of ergonomic research aims at the identification of general relationships between internal