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

BACKGROUND: Adjustable 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. METHODS: Thirty 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. RESULTS: Sum20 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. CONCLUSION: Extremely high or low teaching boards have tendencies of inducing musculoskeletal shoulder discomforts.

Evaluation of selected cardiopulmonary and perceived exertion responses to four infant carrying methods utilised by African Mothers.

Various infant carrying methods (ICMs) are utilised for childcare. Effects of these ICMs on the cardiopulmonary system are not known. This study evaluated cardiopulmonary and perceptual responses to four ICMs (back, front, side and in-arms) among 30 young females (18-35 years) while walking with a 6 kg simulated infant. Diastolic blood pressure (BP) responses were significantly different (p = .009) across the four ICMs, with the back ICM eliciting highest response. Heart rate, respiratory rate and systolic BP responses were not significantly different (p > .05) across the ICMs. Participants perceived the in-arms ICM as the most exerting. Body weight (p = .036) and body mass index (BMI) (p = .011) significantly correlated with systolic BP responses during the side ICM while age significantly (p = .036) correlated with heart rate changes during the in-arms ICM. Back ICM may pose more risk of diastolic BP dysfunctions. Increased body weight and BMI result in decreased systolic BP responses. IMPACT STATEMENT What is already known on this subject? Infant carrying (IC) has been associated with increased energy cost, biomechanical changes and musculoskeletal injuries. There is paucity of data on the cardiopulmonary responses to IC. What do the results of this study add? Back ICM resulted in higher responses in diastolic blood pressure. During the side ICM, participants' systolic BP decreased with increasing body weight and BMI values. Increased age resulted to decreased heart rate responses during the in-arms ICM. What are the implications of these findings for clinical practice and/or further research? There is need for effective monitoring of the cardiopulmonary parameters during IC tasks, especially among women with cardiopulmonary dysfunctions. Women with diastolic dysfunctions should be discouraged from utilising the back ICM. It is necessary for further studies to evaluate infant carrying-related cardiopulmonary responses relative to various components of IC practices, including weight of infant, maternal anthropometric characteristics and duration of IC tasks during each infant carrying method.