Assessing Musculoskeletal Health Risks in Standing Occupations ^†

Abstract

This study investigates the risk of developing musculoskeletal disorders (MSDs) in individuals performing standing tasks, with a focus on real-time posture assessment using motion capture technology. Improper body posture and repetitive movements during daily work activities can impose strain on the musculoskeletal system, increasing the likelihood of discomfort and long-term injury. Data were collected from five male and female participants using the Perception Neuron motion capture system, with body-mounted sensors tracking posture and movement. Joint angles were calculated to distinguish between correct and incorrect postures based on ISO 11226:2000 ergonomic guidelines. Key physical risk factors identified included prolonged forward trunk inclination, elevated arm positions, and repetitive actions. The analysis revealed that participants frequently adopted moderate- to high-risk postures, especially when working at non-ergonomic desk heights, suggesting a heightened risk of MSDs such as back and upper limb pain. These findings underscore the importance of real-time ergonomic monitoring and adaptive workstation design to reduce musculoskeletal risks in standing work environments.

1. Introduction

The working posture that each employee takes is important, as incorrect working posture can lead to musculoskeletal disorders (MSDs). The correct posture is a posture that avoids body tension during work. Incorrect posture, especially when maintained extensively, causes pain or other MSD symptoms. Proper posture reduces excessive stress on the joints and muscles of the body, thereby reducing pain and minimizing the risk of injury [1].

Physical risk factors include working with raised arms and repetitive movements [2,3]. According to Frössler [4], upper body postures lead to functional disorders in the joints of the vertebral body and higher biomechanical loads. Signs of wear and tear that appear earlier result in damage, resulting in discomfort [5]. The commercially available Perception Neuron motion capture (Mo-Cap) system is a cost-effective and easy-to-use motion analysis option.

Studies have shown that the Mo-Cap system is a valid method for estimating most of the range of motion of the upper body up to 5° [6,7,8,9]. Qualitative or quantitative measurements are required for any procedure involving human motion capture (Mo-Cap). Quantitative analysis requires the measurement of biomechanical variables such as postural angles, pressure distribution, moments, and forces produced by the human body [10].

Optoelectronic motion capture is currently considered the gold standard in measuring and quantifying human kinematics in clinical medicine. Retroreflective markers are attached to the body and tracked by cameras that collect data on the position of the marker. The positional data can then be used to perform biomechanical analysis under both static and dynamic conditions [11,12,13,14].

The present study aimed to develop an automated real-time system for assessing ergonomic posture during standing work. A methodology was established to assess the posture of participants in three risk zones—no risk, moderate risk, and high risk—based on body position. Motion capture technologies, including Perception Neuron, Axis Neuron, and Unity, were used to accurately track and analyze body movements in real time. Experiments were conducted at different desk heights to highlight the importance of choosing the appropriate desk height for standing work.

The motivation behind this study stems from the growing need to assess the postural-related risks and optimize ergonomic conditions in standing work environments, which can significantly impact the musculoskeletal health and overall productivity of workers.

2. Material and Methods

This study evaluates the impact of two desk height configurations on ergonomic posture and comfort during standing work among participants with varying anthropometric characteristics. The aim is to determine how differences in body height, limb length, and torso dimensions influence posture and physical strain during task performance.

An automated real-time posture assessment system based on motion capture technology was used for data collection. The Perception Neuron and Unity platforms were employed to track full-body movement via body-mounted sensors. Each participant performed standardized tasks at two desk height levels designed to simulate ergonomic and non-ergonomic conditions.

Postural analysis focused on deviations from neutral alignment and the effect on the spine, shoulders, and upper limbs. The data were used to evaluate whether fixed desk heights are universally appropriate or if adjustments are necessary based on individual body proportions.

Figure 1 presents the structure of the experimental workflow. The process begins with the setup of a motion capture environment for upright task execution, where full-body movement is recorded using Perception Neuron sensors. The physical configuration, including markers and the workspace, is digitally integrated through Axis Neuron and Unity, which are synchronized for data collection and visualization. Two scenarios are tested, each involving a different desk height determined by the participant’s body measurements. Collected data are post-processed and analyzed to assess trunk inclination and overall posture in both conditions, evaluating the influence of desk height on body alignment.

2.1. Experimental Procedure

The experiment was conducted in a specially designated and fully equipped laboratory at the Technical University of Varna, selected to meet the specific requirements of the study. This facility provided all necessary equipment and resources for accurate data collection and analysis. All participants provided informed consent before data collection.

Five volunteers with varying body heights participated in the experiment while performing tasks in a standing position. The Perception Neuron motion capture system was used to collect data via multiple sensors attached to key anatomical points on the body. Each participant completed tasks under two conditions, with desk heights selected based on their anthropometric measurements. This approach allowed for the assessment of postural responses in both ergonomic and non-ergonomic working environments.

To enhance the visualization of the work process during the execution and preparation of the experiment, a schematic representation of the sequence of actions was created. Motion data were processed using Axis Neuron and Unity software, which provided synchronized data acquisition and visual analysis.

The hardware setup included the Perception Neuron sensor system, consisting of multiple inertial sensors mounted on elastic bands, enabling non-restrictive and precise tracking of body movement. Unity software, synchronized with Axis Neuron, was used to calculate and visualize joint angles and postural deviations during task execution.

At the beginning of each session, the system was calibrated to account for the participant’s unique anatomical characteristics, ensuring the accuracy of motion capture. The example shown on Figure 2 presents a visualization during the session of a 160 cm-tall female.

During the study, the ISO 11226:2000 ergonomics standard was employed to evaluate both correct and incorrect working postures, as well as the corresponding joint angles adopted by participants. According to this standard, posture-related risk levels are categorized by angle thresholds: angles between 0° and 20° are classified as low risk and are displayed in green; angles between 20° and 60° represent a moderate risk and are shown in yellow; while angles exceeding 60° indicate a high-risk posture and are marked in red.

Figure 3 illustrates the ISO 11226:2000 reference framework for assessing static working postures. Angle measurements are based on the neutral zero method, wherein all joint movements are measured relative to a predefined zero position [15]. This neutral posture corresponds to a healthy individual standing upright, with arms relaxed at the sides, thumbs pointing forward, feet positioned parallel, and gaze directed straight ahead. From this position, movement in either direction within a given anatomical plane is recorded as positive or negative.

An exception to this standard was applied to the elbow joint: flexion and extension were measured from a neutral position at 90°, as this angle better reflects the natural and optimal range of motion for performing manual tasks [16]. This adaptation aligns with recommendations for evaluating functional movements in real-world work scenarios.

To ensure that the height of the workbench supports a proper upright working posture, it must fulfill specific ergonomic conditions, including minimizing trunk inclination and maintaining joint angles within the low-risk zone, as defined by ISO 11226:2000. Examples of correct and incorrect postures, as visualized through the developed software application for posture assessment, are presented in Figure 4.

2.2. Participants

The survey was conducted in July 2024 in Bulgaria, utilizing an experimental design involving healthy subjects (n = 5). The study comprised five volunteers, including two men and three women. Among the women, two had heights of 160 cm and 165 cm, while the third measured 175 cm. The male participants were 180 cm and 185 cm tall, respectively. Consequently, the shortest volunteer was 160 cm, and the tallest was 185 cm, yielding an average height of 173 cm.

All participants confirmed that they did not experience any lower back pain, inflammatory conditions, or other musculoskeletal disorders, and none were pregnant. Informed consent was obtained from all participants prior to their involvement in the study. During the experiment, participants were instructed to adopt their usual upright working posture.

3. Results

To assess the influence of work surface height on participants’ postures, trunk inclination angles were recorded as volunteers performed a sorting task while standing. This task required participants to categorize small elements by type on work surfaces of two different heights: 72 cm and 91.5 cm. These heights were selected to reflect ergonomic and non-ergonomic conditions based on the anthropometric characteristics of the participants. The standard ergonomic height for standing workstations is approximately 85 cm, typically suitable for individuals around 160 cm tall.

In this study, two participants were 160 cm and 165 cm tall and performed the task on the 72 cm surface, representing a lower-than-ideal height. Three participants—measuring 175 cm, 180 cm, and 185 cm tall—used a surface height of 91.5 cm, which is closer to the ergonomic recommendation for their stature.

Throughout the experiment, participants were instructed to maintain their usual upright working posture. Trunk inclination angles were evaluated using the automated real-time posture assessment system in accordance with ISO 11226:2000. Angles were classified into three risk zones:

• 0–20° (green zone): no risk;
• 20–60° (yellow zone): moderate risk;
• >60° (red zone): high risk.

Table 1. Measured trunk inclination angles at workbench heights of 72 cm and 91.5 cm.

Workbench Height of 72 cm
Volunteers	α Min	α Max	Average	Standard Deviation
height 160 cm	22	28	25.3	2.4535
height 165 cm	23	27	25	1.6329
height 175 cm	39	46	43	2.8674
height 180 cm	38	47	42	3.6817
height 185 cm	36	58	47.10	8.9815
Workbench height of 91.5 cm
height 160 cm	0.53	0.60	0.57	0.0432
height 165 cm	0.36	0.63	0.50	0.1102
height 175 cm	3	7	4.80	1.6357
height 180 cm	1	6	3.75	2.0446
height 185 cm	19	24	21.7	2.0512

presents the measured trunk inclination angles of participants performing a standing task at two different workbench heights (72 cm and 91.5 cm), categorized by participant height, including statistically calculated values for minimum, maximum, average, and standard deviation.

From the results in Table 1, it is evident that participants with a height of 160–165 cm working at a 91.5 cm desk maintained trunk inclination angles between 0.36° and 0.63°, placing them comfortably within the no-risk zone. Taller participants (175–185 cm) also remained mostly in the green zone, though the 185 cm volunteer briefly crossed into the moderate-risk zone with angles ranging between 19° and 24°.

In contrast, when using the 72 cm desk, participants measuring 160–165 cm consistently exhibited moderate-risk trunk inclinations, ranging from 22° to 28°, with occasional posture corrections that temporarily returned them to the risk-free zone (15–20°). Taller participants (175–185 cm) demonstrated significantly higher inclination angles, averaging between 42° and 47°, with peak values reaching up to 58°, placing them predominantly in the moderate- to high-risk zones. Notably, the tallest volunteer (185 cm) operated at the upper threshold of the moderate-risk zone and briefly entered the high-risk red zone.

An example of a volunteer maintaining a neutral posture at the optimal workbench height (91.5 cm) is shown in Figure 5a, whereas Figure 5b illustrates a moderate-risk forward inclination at the lower 72 cm workbench height.

These findings suggest that a fixed desk height cannot accommodate the ergonomic needs of individuals with varying statures. While a 91.5 cm desk height is suitable for individuals around 160–165 cm in height, it becomes suboptimal for taller participants, who begin to approach or exceed moderate-risk posture thresholds. Conversely, a 72 cm desk universally places participants in postures associated with greater risk.

Therefore, adjustable-height desks are recommended to accommodate individual anthropometric profiles. Such adaptability helps maintain safe trunk angles, promotes comfort during prolonged standing work, and may reduce the risk of developing musculoskeletal disorders.

The sample size of five participants was selected based on the pilot nature of the study and the intensive data collection protocol involved in full-body motion tracking. The use of high-fidelity motion capture equipment required individual calibration and extensive post-processing, limiting the feasible number of participants without compromising data quality. This controlled setting allowed for the detailed observation of postural changes under different ergonomic conditions. Future studies will expand the sample size to validate these findings across broader populations and statistical analyses.

4. Conclusions

This study demonstrated the effectiveness of an automated, sensor-based system for real-time ergonomic assessment of working posture in a standing position. Using the Perception Neuron motion capture system integrated with Axis Neuron and Unity software, we successfully tracked full-body movements and quantified trunk inclination angles under different workbench height scenarios. The automated system enabled the precise, objective evaluation of postural risks based on ISO 11226:2000 standards.

The results confirmed that workbench height significantly impacts trunk posture and ergonomic risk levels. While a 91.5 cm desk height was appropriate for shorter participants (160–165 cm), it proved suboptimal for taller individuals, who approached or exceeded moderate-risk thresholds. Conversely, the 72 cm desk led to increased forward inclination across all participants, often entering moderate- and high-risk zones.

These findings highlight the importance of individualized ergonomic assessments and support the use of adjustable-height workbenches to accommodate diverse anthropometric profiles. The proposed automated system proved to be a valuable tool for continuously monitoring and analyzing posture, enabling data-driven recommendations for ergonomic improvements.