Determining safe teaching board heights through electromyographic analysis of the shoulder muscles

Abstract

BackgroundAdjustable teaching boards have been recommended as an ergonomic practice geared at reducing the incidences of teaching-related shoulder musculoskeletal disorders among teachers. However, there are no standards guiding choice of appropriate teaching board heights. This study was aimed at evaluating shoulder muscle activities in response to five teaching board heights. MethodsThirty participants performed writing activities on five different board heights (Diff10 = standing height minus 10% of standing height; NormH = participant's standing height; Sum10 = standing height plus 10% of standing height; Sum20 = standing height plus 20% of standing height; Sum25 = standing height plus 25% of standing height). Electromyographic analysis of the anterior deltoid (AD), upper trapezius (UT), serratus anterior (SA) and pectoralis major (PM) muscles were performed simultaneously during each task. Data were analyzed with one-way ANOVA and independent T-test at p < 0.05. ResultsSum20 board height significantly (p < 0.001) elicited the highest activities in the AD (19.35 ± 11.26%) and UT (29.06 ± 29.53%) muscles while SA (20.37 ± 10.87%) and PM (20.86 ± 12.17%) muscles were most active at Sum25 board height. SA and PM muscles progressively increased with increasing board heights while AD and UT muscles showed alternating patterns of activation at increasing board heights. For safe ergonomic practices, recommended teaching board heights should be within the range of NormH and Sum10. ConclusionExtremely high or low teaching boards have tendencies of inducing musculoskeletal shoulder discomforts.