Electromyographic activity of the neck muscles: Effects of varying standing height-derived teaching board heights.

Background: Despite the increasing emergence of modern facilities, the ancient practice of writing on a teaching board is still common in the teaching profession. Ergonomic guidelines of this practice are required for the prevention of work-related neck musculoskeletal disorders inherent of teachers.

Objective: This study investigated the effects of varying teaching board heights on the activities of the neck muscles.

Methods: Thirty participants (15 males and 15 females) participated in this experimental study. Each performed writing tasks on a teaching board set at five different heights derived from their standing height (SH) [(D 10 = SH minus 10% of SH; Norm H = SH; Sum 10 = SH plus 10% of SH; Sum 20 = SH plus 20% of SH; Sum 25 = SH plus 25% of SH)]. Electromyographic (EMG) activities of both components of the sternocleidomastoid and upper trapezius muscles were measured during each task. Asymmetry ratio of right and left muscle components were determined. Data were analyzed with one-way ANOVA.

Results: EMG activities of the four muscles as well as their asymmetry ratios significantly (p< 0.01) increased with increasing board heights.

Conclusion: Teaching board-related tasks have increased possibilities of inducing neck disorders when performed beyond Norm H vertical heights.