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Ergonomists and researchers often utilize electromyographic (EMG) recordings to produce estimates of muscular work load in occupational exposure assessment. Prolonged measurements, possible with recent technological advances in portable data acquisition and compact memory storage technologies, require efficient data reduction methods not always available in commercial software packages. The Iowa EMG Analysis Program (IEAP) was created to provide researchers the means to incorporate multiple processing techniques suited for the analysis of prolonged EMG measurements. IEAP currently includes subroutines to calculate the amplitude probability distribution function, exposure variation analysis, clustered exposure variation analysis, and gaps analysis profiles for up to four channels of root-mean-square processed EMG data. Data management functions include the creation of customized hypertext markup language (HTML) documentation and text files able to seamlessly incorporate analysis results into existing statistical software packages. IEAP is a powerful EMG analysis tool ideally suited for ergonomists and researchers involved in occupational ergonomics studies.

The purpose of this cross-sectional study was to compare the observed associations between upper trapezius muscle activity, as estimated with several summary measures obtained from surface electromyography (EMG), and self-reported neck/shoulder pain among a sample of 231 manufacturing workers. EMG methods used in this study included mean root-mean-square amplitude, the amplitude probability distribution function (APDF), EMG gaps analysis, and clustered exposure variation analysis. The observed seven-day prevalence of neck/shoulder pain was 13.9%. Of the EMG summary measures, only the 90 th percentile of the APDF was significantly associated with symptoms, with crude and adjusted odds ratios of 2.57 (1.02–6.49) and 2.78 (1.07–7.21) per natural log unit, respectively. This study was largely inconclusive due to the similarity in the distributions of the summary measures between symptomatic and non-symptomatic participants, and explicit measures of posture and repetition may produce stronger associations with symptoms.

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