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OBJECTIVES To determine the activity of the upper trapezius, serratus anterior, anterior deltoid, biceps brachii. and lower trapezius muscles in healthy adults during below-the-knee assembly work. METHODS Fifteen right-handed male subjects participated in this study. The electrical activities, measured by EMG, of the right upper trapezius, serratus anterior, anterior deltoid, biceps brachii. and lower trapezius were measured during below-the-knee assembly work at four workstations of varying height and distance from the participant (workstation 1, below-the-knee assembly work with a height of 15 cm above the floor and a reach distance of 30 cm; workstation 2, height of 15 cm and distance of 45 cm; workstation 3, height of 30 cm and distance of 30 cm; workstation 4, height of 30 cm and distance of 45 cm). Muscle activity at the four workstations was represented as a percentage of the reference voluntary isometric contraction (RVIC). RESULTS Height: Upper and lower trapezius activity increased significantly during below the knee assembly work as height above the floor increased. The activities of the serratus anterior and biceps brachii muscles increased significantly during low-height below-the-knee assembly work. Distance: The activities of the upper trapezius, serratus anterior, anterior deltoid and biceps brachii increased significantly during below-the-knee assembly work at a far distance (45 cm). The lower trapezius muscle activity increased significantly during below-the-knee assembly work at a close distance (30 cm). CONCLUSIONS Below-knee workers should engage in work close to themselves, since distance appears to be a stronger risk factor for injury than height above the floor.

Changes in Neck and Back Pain, Cervical Range of Motion and Cervical and Lumbar Flexion- relaxation Ratios after Below-knee Assembly Work: Seung-je SHIN, et al. Department of Physical Therapy, The Graduate School, Inje University, Republic of Korea—Objectives: This study examined the changes in neck and back pain visual analog scale (VAS) scores, cervical range of motion (CROM), cervical flexion-relax- ation ratio (FRR) and lumbar FRR after below-knee assembly work. Methods: Fifteen young male workers were recruited. Neck and back pain VAS scores, active CROM and cervical and lumbar FRRs were measured in all subjects once before and once after 10 minutes of below-knee assembly work. Results: The VAS scores for both neck and back pain increased signifi- cantly with below-knee assembly work. The CROM for all measures decreased significantly with below-knee assembly work. Both the cervical and lumbar FRRs on the left and right sides decreased significantly with below-knee assembly work. Conclusions: We postu- late that 10 minutes of below-knee assembly work can increase neck and back pain and cause changes in the active CROM and cervical and lumbar FRRs. (J Occup Health 2014; 56: 150-156)

BACKGROUND Although overhead work is closely related to musculoskeletal disorders, it is difficult to avoid these postures in daily working conditions. In industrial tasks that require elevated arm postures above shoulder height, flexibility in the location of the task is necessary. OBJECTIVE This study investigated the sternocleidomastoid, upper trapezius, lower trapezius, and anterior deltoid, serratus anterior muscle activities during overhead work involving four different height and distance locations performed by healthy adult participants. METHODS Eighteen young male right-hand-dominant workers were recruited. The right upper trapezius, lower trapezius, serratus anterior, anterior deltoid, and sternocleidomastoid muscle activities were measured under for overhead work condition (Location 1: overhead work with a height of 10 cm above the head of each subject and distance of 15 cm, Location 2: overhead work with a height of 10 cm above the head of each subject and distance of 30 cm, Location 3: overhead work with a height of 20 cm above the head of each subject and distance of 15 cm, Location 4: overhead work with a height of 20 cm above the head of each subject and distance of 30 cm). RESULTS In Location 3, there was significantly higher neck extension range of motion compared to Location 1, Location 2 and Location 4. In Location 1, the activities of the upper trapezius, lower trapezius, serratus anterior, anterior deltoid, and sternocleidomastoid muscles were significantly lower than those in Location 3 (p

[Purpose] The purpose of this study was to compare the activity of the shoulder and trunk muscles in two push-up positions: standard push-ups and push-ups with the trunk flexed. [Subjects] Fifteen young adult males participated in the study. [Methods] This study measured the clavicular and sternocostal portions of the pectoralis major, the serratus anterior, and the rectus abdominis during push-ups under the two conditions. [Results] The activity of the sternocostal portion of the pectoralis major and that of the rectus abdominis were significantly greater under Condition 1 than under Condition 2. The activity of the clavicular portion of the pectoralis major and that of the serratus anterior were significantly greater under Condition 2 compared with Condition 1. [Conclusion] These results indicate that exercises can selectively activate muscle parts under different clinical situations.

[Purpose] This study investigated the effect of different gait speeds on the muscle activities of the latissimus dorsi and gluteus maximus muscles in relation to the posterior oblique sling system. [Subjects] We recruited 14 young adult males. [Methods] We measured the left latissimus dorsi muscle activity and right gluteus maximus muscle activity of all subjects while they walked on a treadmill at speeds of 1.5 km/h, 3.5 km/h and 5.5 km/h. [Results] There was a significant increase in latissimus dorsi muscle activity with a treadmill speed of 5.5 km/h compared with 1.5 km/h and 3.5 km/h. The gluteus maximus muscle activity significantly increased in the order of 1.5 km/h < 3.5 km/h < 5.5 km/h. [Conclusion] The present results indicate that arm swing connected to increasing gait speed influences the muscle activity of the lower limbs through the posterior oblique sling system.

This study examined the changes in pressure pain in the upper trapezius muscle, cervical range of motion, and cervical flexion-relaxation ratio after overhead work. 14 workers were recruited. Pressure pain in the upper trapezius muscle, active cervical range of motion, and cervical flexion-relaxation ratio were measured in all subjects once before and once after overhead work. The pressure-pain threshold of the left upper trapezius muscle was 8.6 ± 2.5 lb before overhead work and 7.3 ± 2.4 lb after overhead work; that of the right upper trapezius muscle was 8.8 ± 2.9 and 7.3 ± 2.8 lb, respectively, revealing a significant decrease in pressure-pain threshold with overhead work. All cervical range of motion measures decreased significantly with overhead work. The cervical flexion-relaxation ratio on the left side was 1.3 ± 0.2 before overhead work and 1.1 ± 0.2 after overhead work; the respective values for the right side were 1.4 ± 0.5 and 1.2 ± 0.3 before and after overhead work, revealing a significant decrease with overhead work. We postulate that overhead work can reduce the pressure-pain threshold in the upper trapezius muscle and cause changes in the cervical range of motion and cervical flexion-relaxation ratio.

[Purpose] This study was performed to determine which set of below-knee working conditions minimizes upper extremity muscle activity and which of upward- or downward-direction workstations poses the greater risk of upper extremity disorder. [Subjects] The study population consisted of 15 young male workers. [Methods] EMG activities of the right anterior deltoid, biceps brachii, and lower trapezius muscles were measured in two below-knee assembly workstation positions. [Results] The anterior deltoid and biceps brachii muscle activities of Position 1 were significantly higher than those of Position 2. The lower trapezius muscle activity of Position 2 was significantly higher than that of Position 1. [Conclusion] Upward-direction workstations appear to pose a greater risk of upper extremity disorder than downward-direction workstations in below-knee assembly work.

[Purpose] We investigated upper-extremity muscle activity during below-knee assembly work performed by healthy adults at three different reach distances evaluate the physical risk factors associated with neck and shoulder disorders of reach distances. [Subjects] Sixteen young male workers were recruited. [Methods] Activities of the right upper trapezius, anterior deltoid, and biceps brachii muscles were measured during below-knee assembly work at the three different reach distances. [Results] The normalized EMG data of the upper trapezius, anterior deltoid, and biceps brachii muscles generally increased significantly as the reach distance at which the assembly work was performed increased. [Conclusion] Below-knee workers should engage in work that involves shorter (nearer) reach distances.