Work-related musculoskeletal disorders (WRMDs) refer to muscle, bone, joint, ligament, tendon, or nerve pain that is induced or aggravated by work [1]. Pain caused by WRMDs affects physical health, leading to reduced functional capacity and vitality. Moreover, it also affects mental health, resulting in lower satisfaction with interpersonal relationships and home life and cause additional cost burdens, ultimately reducing an individual's quality of life [2–4]. WRMDs are known to be one of the main causes of work absence [5, 6]. Buckle and Devereux [7] estimated that 45% of all absences associated with occupational diseases were due to WRMDs. WRMDs are associated with reduced productivity in the society [8, 9]. However, although musculoskeletal disorders can cause problems at the personal and socioeconomic levels, they are significantly underreported [10].

Biomechanical exposure, which is associated with WRMDs, includes static posture; repeated pushing, pulling, lifting, and neck bending [11]; highly repetitive work; and forceful exertion in work [12]. In addition, workplace factors (e.g., time pressure, poor work/rest schedule, and low job control), physical factors (e.g., old age and elevated body mass index), and psychosocial stress have also been reported as risk factors of WRMDs [13]. A study has reported that these ergonomic risk factors are present in workplaces for cameramen and that they affect the incidence of WRMDs among cameramen [14]. Another study has reported that because cameramen perform physically demanding tasks and thus experience high levels of physiological stress, their occupation must be classified as heavy work [15].The environment for making TV programs in Korea lacks production costs and staff, giving cameramen long working hours and short break times. This increases the risk of work-related musculoskeletal disorders in cameramen [13].

However, very few studies have included cameramen as research subjects, and no study has directly compared WRMDs in cameramen and other workers. The office workers were selected as a control group because of their lower physical demands compared to other occupations [16–18]. Therefore, we compared the incidence and severity of WRMDs among cameramen and office workers.

Cameramen had more tenure (year) and daily working hours compared to office workers. They also had more incidence of WRMD symptoms than office workers. No significant difference in all other variables was found between the two groups (Table 1).

The subjects' tasks were assessed using an ergonomics assessment tool (MORF). The high ergonomic-risk group for the upper extremities comprised a significantly higher proportion of cameramen (52.7%) than office workers (28.0%). The high ergonomic-risk group for the waist and the lower extremities also comprised a significantly higher proportion of cameramen (43.4%) than office workers (21.3%) (Table 2).

Furthermore, the high-risk WRMD group for the upper extremities comprised a higher proportion of cameramen (32.6%) than office workers (11.0%). The high-risk WRMD group for the waist+lower extremities also comprised a higher proportion of cameramen (24.0%) than office workers (9.1%). The proportion of cameramen was significantly higher than that of office workers in the high-risk groups for all body parts except the hand/wrist/finger (Table 3).

In the age-adjusted model, the OR for cameramen in the high-risk WRMD group relative to that for office workers was 4.03 (95% CI: 2.17–7.49) for the upper extremities and 3.18 (95% CI: 1.62–6.21) for the waist+lower extremities. The ORs by body parts were 3.38 (95% CI: 1.49–7.70), 3.85 (95% CI: 1.92–7.72), 2.77 (95% CI: 1.37–5.57), and 5.11 (95% CI: 1.40–18.66) for the neck, shoulders, waist, and the legs/feet, respectively, and were all statistically significant, except for the OR for hands/wrists/fingers. In the multivariate model, the ORs for cameramen in the high-risk WRMD group relative to that for office workers were 3.50 (95% CI: 1.76–6.96) and 2.43 (95% CI: 1.14–5.12) for the upper extremities and waist+lower extremities, respectively, and were all statistically significant. The ORs by body parts were 3.11 (95% CI: 1.28–7.57), 3.90 (95% CI: 1.79–8.47), and 4.23 (95% CI: 1.04–17.18) for the neck, shoulders, and legs/feet, respectively, and were all statistically significant, except for the ORs for the hands/wrists/fingers and the waist (Table 4).

Previous studies have measured the level of physiological stress experienced by cameramen in terms of heart rate and oxygen consumption and classified cameramen's tasks as physiologically heavy work [15], analyzed occupational suprascapular nerve entrapment among cameramen [22], and identified ergonomic factors and physical burden as risk factors of WRMDs in cameramen, which were found to affect the shoulders most commonly [14]. However, these studies limited their research subjects to cameramen only. In the present study, we compared WRMDs between cameramen and office workers and found that the risk of WRMDs was higher for cameramen. When break time is reduced due to long working hours, musculoskeletal fatigue can occur and induce WRMDs [23]. Chronic musculoskeletal fatigue can lead to accumulated stress on muscles and tendons and subsequently, reduced blood flow in the corresponding areas as work experience and age increase. Eventually, they cause pain and poor function by inducing localized muscle fatigue [24].

Ergonomic stress in the work environment is a risk factor for WRMDs [13]. The biomechanical risks of WRMDs include repetitious and forceful work, awkward or sustained posture, and mechanical pressure [13]. The cameramen's jobs are associated with these risk factors. Cameramen can also be exposed to ergonomic risks depending on the type of camera and filming methods they use. Standard studio cameras used in studios have wheels attached to them for mobility. Although these cameras are usually used in the erect state, cameramen are forced to repeatedly use pulling and pushing forces to change the filming angle and distance. While filming, they must twist their bodies and tilt their head up to look at the viewfinder for monitoring. There are three main methods of outdoor filming: filming using a tripod, filming by directly holding the camera, and filming using a jimmy jib camera. When filming with a camera fixed in a tripod (Electric News Gathering Camera, Electronic Field Production camera, Electric cinematography), cameramen must squat or bend their waist to adjust the height according to the position of the subject, and thus cannot film in a comfortable posture. Their bodies twist, and their necks bend downward to look at the viewfinder. When filming by directly holding a camera (Electric News Gathering Camera), cameramen must carry the weight of the camera, which is over 10 kg. They usually place the camera on their right shoulder for a long period of time without moving and must use different postures such as lifting the camera above the shoulder or lowering it to below the waist or knee level depending on the situation. GK Karatas and F Gogus [22] proposed that these risk factors induce suprascapular nerve entrapment among cameramen. Meanwhile, a jimmy jib camera in the shape of a long lever is used to get an overall shot from high places. A weight is added to one end of the lever and a camera at the other end to adjust the camera height. It is the cameramen's job to lift the weight above the head or lower it below the knees. Outdoor filming requires continuous angle adjustment, focus, and light exposure before the actual shooting begins. Therefore, they should be considered as working hours for the cameramen other than moving hours and resting hours. And the cameramen's filming posture can vary for each scene, each angle.

Office workers can also develop musculoskeletal symptoms of the waist, neck, shoulders, and hands/wrists/fingers due to long hours of using computers [25–27]. However, as can be deduced from the characteristics of cameramen's tasks described earlier, cameramen appear to be at higher ergonomic risk than office workers and thus showed higher ORs for WRMDs of the neck, shoulders, and legs/feet in this study. The reason why the risk of WRMDs was high for the neck may be that cameramen look downward or upward while filming. The shoulders were susceptible to WRMDS possibly because cameramen place the cameras on their shoulders for long periods. Meanwhile, the reason why the risk of WRMDs was high for the legs/feet may be that cameramen often have to stand or squat, whereas office workers spend most of their working hours sitting.

The present study had several limitations. First, musculoskeletal symptoms and ergonomic risk factors were assessed based on self-reported answers. Subjects may have overreported their symptoms and the ergonomic aspects of their occupations. However, because it was difficult to diagnose the subjects with a specific musculoskeletal disorder and cameramen performed a wide range of tasks, there were limits to assessing their symptoms using the Rapid User Limb Assessment [28] or the Rapid Entire Body Assessment [29]. As such, it was difficult to use objective markers. In the following study, it would be helpful to use an objective evaluation tool, such as the video-based observation method [30]. Because different kinds of cameras used for different tasks were clustered to one group and assessed together in this group, future research must divide them further according to their specific tasks. Lastly, all female subjects were excluded, and only male subjects were studied. However, had women, who have higher sensitivity to musculoskeletal symptoms than men [13], been included, the risk of musculoskeletal symptoms among cameramen would have increased. Thus, it will not be difficult to obtain results even when subjects are limited to men only.

Due to media advancements and increased value of media contents, the demand for cameramen has increased. However, research on cameramen, who work in unfavorable work environments that impose long working hours and short break time, who perform ergonomically dangerous tasks that involve making awkward postures and withstanding heavy weights, and who are exposed to various risk factors for WMRD because of the nature of their work, is lacking. In this study, the WRMD symptoms and ergonomic factors were assessed to not only demonstrate that the risk of WRMDs is higher among cameramen than among office workers, but also to show that the tasks performed by cameramen pose high ergonomic risks. No study has directly compared musculoskeletal symptoms between cameramen and other occupations. Confounding effects were minimized by comparing the cameramen with office workers from the same broadcasting companies.

Cameramen were at higher risk for WRMDs than office workers. The risk of WRMDs of the shoulders, neck, and legs/feet was higher than that of other body parts. The working hours of cameramen should be reduced, and the workplace environments with high ergonomic risks should be improved. Furthermore, prevention and follow-up management of WRMDs among high-risk occupations such as cameramen are important. Management of WRMDs affecting the neck, shoulders, and legs/feet, which are highly susceptible to WRMDs, may be effective.