BACKGROUND: According to a recent research, manual working with high levels
of static contraction, repetitive loads, or extreme working postures
involving the neck and shoulder muscles causes an increased risk of neck and
shoulder musculoskeletal disorders.
OBJECTIVE: We investigated the effects of the forwardly worktable position
on head and shoulder angles and shoulder muscle activity in manual material
handling tasks.
METHODS: The forward head and shoulder angles and the activity of upper
trapezius, levator scapulae, and middle deltoid muscle activities of 15
workers were measured during performing of manual material handling in two
tasks that required different forward head and shoulder angles.
RESULTS: The second manual material task required a significantly increased
forward head and shoulder angle. The upper trapezius and levator scapulae
muscle activity in second manual material task was increased significantly
compared with first manual material task. The middle deltoid muscle activity
in second manual material task was not significantly different compared with
first manual material task.
CONCLUSIONS: Based on this result, the forward head and shoulder angles
while performing manual work need to be considered in selection of the
forward distance of a worktable form the body. The high level contractions
of the neck and shoulder muscles correlated with neck and shoulder pain.
Therefore, the forward distance of a worktable can be an important factor in
preventing neck and shoulder pain in manual material handling workers.
