1. Introduction
Work-related musculoskeletal disorders (WMSD) are a high prevalence among supermarket cashiers [
1,
2]. This is also a public health problem due to the high number of professionals conducting such activities. In fact, in Portugal, in 2021, the food retail sector accounted for 1760 retail food trade units in operation, and employed 84.9 thousand workers [
3]. Additionally, there has been a gradual rise in the number of food retail establishments in recent years, with an average annual growth rate of 0.7% between 2018 and 2023 [
4].
The cashier is responsible for carrying out a set of functions ranging from reading, weighing, and recording the price of goods, as well as packaging and bagging goods for customer convenience, to receiving and verifying payments [
5,
6]. Within the range of tasks undertaken by supermarket workers, the responsibilities of cashiers stand out as posing a significant risk of developing WMSD. According to Lehman et al. [
7], cashiers are among the top 10 occupations with a heightened susceptibility to these disorders.
Body regions most susceptible to injury include the neck, upper limbs (shoulders, elbows, hands/wrists), and lower back [
6,
8,
9,
10]. A study developed in Portugal revealed prevalent musculoskeletal complaints among hypermarket cashiers, including non-specific pain, cervical, and lumbar pain, primarily affecting the shoulder, cervical spine, and lumbar spine [
11]. Additionally, findings showed that neck and back pain significantly hindered cashiers from performing their regular tasks, prompting them to seek medical attention from nurses, doctors, or physiotherapists. Some even had to modify their job responsibilities and reduce their activities at home due to the discomfort caused by severe pain [
6].
The work of a cashier is typically performed at a checkout counter. In this workstation, tasks are characterized by repetitive and monotonous movements of the upper limbs, as well as manual handling of heavy and/or bulky loads [
12]. This, related to the poor checkout design, contributes to musculoskeletal disorders in the neck, shoulders, and wrists [
13]. To address the physical strain caused by sitting and standing, the workstation is designed for the cashier to primarily work in a standing position, with periodic breaks to sit [
13,
14,
15]. This helps to prevent muscle fatigue in the lower limbs during the shift and allows the cashier to alternate positions and rest different muscle groups [
15,
16]. However, to fulfill their job responsibilities, cashiers frequently engage in forward flexion, leaning sideways, and trunk rotation, placing them at risk for developing back pain, as noted by Maciukiewicz et al. [
10] and Rodacki et al. [
12]. Consequently, checkout cashiers commonly experience postural issues due to the inherent strain in their work, which is further exacerbated by improper biomechanics in their workstations [
12].
Despite some checkout counters being replaced by smart solutions, like automated and intelligent systems, such as self-checkout counters, that are reducing their presence in some supermarkets, the work of cashiers is still considered relevant, and their role will not disappear. They serve as the company’s frontline representatives, often being the initial and final point of contact for many customers. Due to their substantial responsibilities and integral role in the organization, they are highly regarded as essential and trusted workers [
17,
18]. Given their pivotal role, it is imperative to enhance their working conditions to ensure the continuity of their job duties and safeguard their health and safety. Therefore, it is critical to better understand the musculoskeletal loadings that cashiers are exposed. Postural analysis holds significant potential as an effective technique for assessing work activities. The assessment of the loads on the musculoskeletal system of supermarket cashiers, considering posture, muscle function and the forces they exert, can contribute to better characterizing the biomechanical component of the risk related to the development of WMSD and can considerably contribute to the implementation of necessary changes. Therefore, having access to observational methods, such as Rapid Entire Body Assessment (REBA) [
19] and Rapid Upper Limb Assessment (RULA) [
20] is advantageous for ergonomists according to Hignett and McAtamney [
19].
This study aimed to understand how checkout design can influence musculoskeletal loadings, characterizing its implications among cashiers with different anthropometric characteristics and dominant hands, as well as among checkouts with different designs and product features.
3. Results
Table 6 presents the RULA and REBA scores derived from the analysis of microtasks conducted at the cashier station. Results denoted the high loads on the musculoskeletal system of cashiers. However, RULA and REBA scores differ according to the microtask under analysis. Tasks requiring the engagement of the entire body (evaluated using REBA) were found to be less detrimental to the assessed cashiers than tasks exclusively involving the upper body (assessed using RULA). However, some of the tasks that required all body movements were classified with high-loading levels. The microtask “Replacing paper rolls in the receipt machine at the checkout counter” demonstrated a propensity for causing physical strain on cashiers, with REBA scores ranging from 7 to 11 (scores varying based on the participant under analysis). This microtask often necessitates cashiers to assume precarious positions, occasionally requiring them to kneel on the floor or adopt a squatting posture. Notably, the participant who exhibited the highest REBA score for this microtask was participant 1, who was taller and younger and only had a few years of work experience.
Table 6 highlights the microtasks that pose the greatest loadings to cashiers, notably “Scanning products”, which received a RULA score of 7, signifying the maximum scoring level for all the assessed participants. This microtask is characterized by continuous wrist rotation, elevated shoulders, and repetitive movements of the upper limbs. When comparing the two checkout counters, no noticeable differences were detected regarding the presence of the conveyor belt. Regarding the selected products, despite conducting a distinct evaluation between lighter and heavier/bulkier items, the resulting values remained equally high.
The evaluation of “Scanning bulky/heavy items, while sitting” was not conducted given the fact that cashiers typically perform this microtask while standing, as it is more convenient and less physically demanding to handle and maneuver products in that posture.
Another critical microtask is “Weighing Fruits and Vegetables”, with RULA scores of 5, 6, and 7 (scores varying based on the participant under analysis). In this activity, cashiers must rotate their trunks to the left to access the scale, further contributing to the ergonomic challenges faced by the cashiers.
Microtasks that appeared to pose lower loadings included “Carrying the cash drawer to the checkout counter”, “Carrying the cash drawer and other materials to the vault room”, and “Cleaning the checkout counter”, as indicated by REBA scores of 4, 5, and 6.
4. Discussion
This study confirms substantial musculoskeletal strain in cashiers, notably in tasks like scanning and weighing, aligning with the existing literature that associates such strain with the development of musculoskeletal disorders [
12,
19,
20]. These findings were already expected, since numerous studies have consistently reported a high prevalence of musculoskeletal symptoms among grocery cashiers [
8,
10].
Higher musculoskeletal loading levels were found for microtasks related to customer service, in particular, the ones of scanning and weighing. These tasks are related to repetitive movements, manual material handling, rotation, and lateral bending of the trunk, as well as difficult reaches [
12]. This, along with insufficient rest and long journeys, is related to musculoskeletal discomfort in the shoulders, neck, and lower back [
10].
In terms of differences among cashiers, a comprehensive analysis unveiled that Participant 1, who was the tallest, youngest, and right-handed, had the highest REBA and RULA values along the different microtasks under analysis. Closely behind was Participant 4, who was left-handed, on the taller side, and older. Concerning hand dominance, Participant 3 was ambidextrous, Participant 4 was left-handed, and the other 3 participants were right-handed. However, this variable demonstrated no influence on the analyzed microtasks, according to the reported values of REBA and RULA.
In this domain, the interaction with the cashiers revealed that older cashiers with longer work experience commonly reported more musculoskeletal complaints, consistent with the existing literature suggesting that these workers are susceptible to musculoskeletal pain and disorders [
6,
24].
It was observed that working in a standing and in a sitting posture conceded consistent RULA assessments for the microtasks involving product scanning. As previously mentioned, these assessments consistently reached the maximum RULA score of 7, indicating that changes in the work environment are required immediately. Relatively to both postures (standing and sitting) in the scanning and weighing microtasks, the results obtained were not expected, since some findings indicate that a standing position offers biomechanical advantages for the upper limbs and trunk [
7,
16]. Nevertheless, the RULA score obtained for these microtasks was consistently high, making it challenging to differentiate between the two postures, both of which were deemed as posing a risk. However, it is important to be aware that is advisable to incorporate a combination of both standing and sitting for optimal working conditions [
7,
16]. This approach mitigates the risk of lower limb muscle fatigue throughout the work shift, underscoring the importance of having chairs available at each checkout station [
7,
16]. In addition, exploring other alternatives such as introducing new chair designs that allow for an intermediate posture between sitting and standing could provide significant benefits, particularly for individuals experiencing discomfort during prolonged standing. Research in this area is warranted. For instance, a recent study by Noguchi et al. [
25] introduced a new chair design, and participants reported a notable reduction in lower leg and lower back discomfort compared to traditional standing positions. Furthermore, the implementation of scheduled rest breaks is essential for cashiers, even given the demanding nature of their work, to safeguard their well-being [
16].
Our findings also demonstrate that taller cashiers presented higher musculoskeletal loadings. This emphasizes the importance of customizing workstations to accommodate the individual anthropometric characteristics of cashiers. Considering this, is imperative that the checkout counter is height-adjustable to guarantee ergonomic and comfortable working postures, as emphasized in the study by Lang et al. [
26]. It is also recommended to investigate the effects of rotating cashiers between mirrored configurations to assess whether this strategy has the potential to mitigate the overloading of one arm [
26].
In the present study, no differences in scores between different checkout conditions were observed. This was because the maximum scoring level was achieved in both, not allowing to distinguish between both designs. This suggests that new design solutions are needed for checkouts.
One contemporary challenge arises from the increasing prevalence of self-checkout stations in supermarkets. Nonetheless, it is crucial to underscore that the significance of cashiers’ roles cannot be overstated. However, the frequent errors and the expectation for customers to assume a more active role at self-checkout counters have resulted in many customers favoring the traditional checkout counter with a cashier, where the checkout process is typically smoother and more reliable [
27]. Additionally, cashiers function as the primary face of the company, interacting with a multitude of customers daily. The enduring importance of this job role highlights the necessity of continuously enhance working conditions, ensuring the seamless execution of their duties while prioritizing their health and safety [
27].
Applying ergonomic principles to the design processes, workplace, and organizational structure serves not only as a response to legal requirements, but also as a strategic alignment with companies’ objectives. Hence, checkout counters should be redesigned with meticulous attention to biomechanical and anthropometric principles [
28].
The results underscore the crucial role of ergonomic checkout counter design, emphasizing the need to tailor it to individual characteristics and advocate for a balanced combination of standing and sitting (as suggested by Lehman et al. [
7], Draicchio et al. [
16], and Cudlip et al. [
29]).
Despite the relevance of this study’s results, it is important to realize that only five cashiers were included in the assessments. These were the workers who voluntarily accepted to be a part of the study and who met the inclusion criteria. To mitigate this effect, a significant number of microtasks were assessed. However, in the future, it will be relevant to better understand the influence of certain variables, including larger comparative samples, such as dominant arm and gender. Additionally, the way the product is held, whether with one or two hands, may influence the results.
The study was limited to the analysis of the biomechanical component of the risk of WMSD in cashiers. Future studies should address other variables, such as psychosocial and organizational risk factors, that also play a relevant role in the risk of WMSD in checkout operators [
9]. Continuous efforts to enhance working conditions, even in the era of self-checkout, are crucial for the health and safety of cashiers.
Additionally, despite the fact that results were limited to the design of the checkouts under analysis, we consider the analyzed checkouts representative of the retail reality in the country. Different results could be obtained in other checkout conditions and with a larger sample.
5. Conclusions
The study emphasizes the significant and negative impact of musculoskeletal loads on cashiers, significantly contributing to the risk of WMSD development. Additionally, it underscores the importance of designing checkout counters respecting ergonomic requirements, considering individual characteristics, and promoting a balanced combination of standing and sitting postures. To significantly reduce the risk of developing these disorders, the checkout counter should offer adjustability in all directions to accommodate 95% of the cashier population. In cases where this is not feasible, the height and reach dimensions should be determined based on the tallest individuals followed by the provision of equipment to adjust the height to accommodate smaller individuals. The workstation should enable cashiers to adopt various safe working postures during task performance while keeping their joints in neutral positions. Task rotation and appropriate resting times are also relevant to prevent WMSD among these professionals.
Experienced and older cashiers frequently reported musculoskeletal complaints, consistent with the literature indicating that cashier workers are prone to musculoskeletal pain and injuries.
The importance of future studies lies in evaluating the compatibility between the dimensions of supermarket checkout counters and the anthropometric measurements of workers. Redesigning supermarket checkouts with meticulous consideration of workers’ anthropometric dimensions is vital to alleviate the physical demands of the job and ensure organizational sustainability. This is crucial to enable older individuals in the retail sector to continue working in favorable conditions and reduce their susceptibility to musculoskeletal injuries. Additionally, it is important to ensure optimal working conditions for newcomers in the retail sector as cashiers, preventing the occurrence of musculoskeletal injuries.
Despite the emergence of self-checkout counters, traditional checkout stations will persist, making it essential to prioritize the safety and health of these operators.