Effects of Different Overhead Work Conditions on the Neck and Shoulder Muscles

[Purpose] This study investigated the upper trapezius muscle and sternocleidomastoid muscle activities during overhead work performed under three different conditions. [Subjects] Ten young overhead workers (five males, five females), aged 22–32 years, were recruited. [Methods] We measured the right side upper trapezius muscle activity and right side sternocleidomastoid muscle activity of all subjects while they performed overhead work under the following conditions: 1) one hand doing overhead work and a fixed neutral neck posture; 2) one hand doing overhead work with maximal neck extension; and 3) two hands doing overhead work with maximal neck extension. [Results] In Condition 3 there was a significant increase in the upper trapezius muscle activity compared to Condition 1;There was also a significant increase in the sternocleidomastoid muscle activity compared to Condition 1 and Condition 2. [Conclusion] Overhead workers should only be asked to do one-handed work that requires a neutral neck posture. A neutral neck posture and a device, such as a monitor or mirror, would reduce the risk of muscle strain from overhead work.