Human Biomechanics Research Articles

Biomechanical analysis and application of image processing technology based on deep learning in the indoor evaluation system of high-rise buildings

In the context of biomechanics and the built environment, understanding the relationship between the indoor space layout of high-rise buildings and human biomechanical responses is crucial. To enhance the quality of the indoor space layout of buildings with respect to human biomechanical comfort and functionality, this paper proposes a method for extracting the characteristics of the indoor space layout of high-rise buildings based on deep-learning image processing. The indoor space layout parameters are not only related to architectural aesthetics but also have implications for human movement and biomechanical behavior. For example, the dimensions and configurations of rooms and corridors can affect gait patterns, body postures, and muscle activations during walking and other activities. According to the extracted indoor space layout parameters, their edge sequences are determined. The image processing algorithm based on deep learning is then used to control the convergence of the characteristic parameters. This process is not only for architectural feature extraction but also to analyze how these features interact with human biomechanics. For instance, the angles and lengths of corridors can influence the turning radii and step frequencies of individuals, which are key biomechanical factors. By extracting the characteristics of the indoor space layout of high-rise buildings, we can evaluate how well the space accommodates human movement and biomechanical needs. The results reveal that the proposed method can effectively extract features relevant to both architecture and biomechanics, and the accuracy in assessing biomechanically relevant features is always higher than 90%. This high accuracy indicates the potential of this method to contribute to the design of indoor spaces that are more conducive to human biomechanical well-being and efficient movement.

Sports biomechanical analysis of knee joint injuries in table tennis players

Table tennis is a fast-paced, explosive sport that puts a lot of strain and stress on players’ lower limbs, particularly their knee joints. This work built a thorough mathematical model to investigate the dynamic and kinematic properties of the knee joint under various motion situations, with the goal of better understanding the biomechanical behavior of the knee joint in table tennis. A model of knee joint motion that takes into account the two degrees of freedom—flexion, extension, and rotation—is put forth based on the concepts of human biomechanics and kinematics theory. This model uses the Newton Euler equation to explain the mechanical behavior of the knee joint and integrates internal forces like muscle forces and external factors like ground reaction forces for torque balance analysis. This study offers a thorough examination of the force distribution and knee joint trajectory in table tennis using numerical simulation techniques. The findings show that the knee joint undergoes considerable compression and shear forces during intense activity, and that the joint’s stress properties vary significantly depending on the kind of movement. This finding is a valuable resource for table tennis players’ knee joint injury prevention and rehabilitation.

Research on innovative design of intelligent wearable products based on human machine engineering and bionics

Designing intelligent wearable products entails integrating human factors, engineering, and bionics to develop ergonomic, efficient and convenient products. Human-machine engineering is a discipline that addresses the integration between the user wearing a particular system and improving the relationship between the user and the system. At the same time, bionics is an approach that aims to mimic biological systems and structures to enhance the performance of a particular product. This research explores the possibility of integrating these specializations to design new and enhanced wearable technology products with improved usability, convenience, and flexibility for practical usage. A detailed analysis of human biomechanics and ergonomic requirements established design parameters to ensure that wearable devices could be seamlessly integrated into daily life without hindering user movement. Bionic principles, such as the flexibility of animal joints and the energy-efficient movements of natural organisms, were applied to optimize the mechanical and structural aspects of the devices. This approach enabled the creation of products that mimic the natural dynamics of the human body, offering improved responsiveness and functionality. Prototypes were developed based on human-centred design principles and evaluated using simulation and testing environments. Wearables such as exoskeletons, bright clothing, and health-monitoring devices were examined for their ability to adapt to various physical conditions and environmental changes. Results demonstrate a significant increase in user comfort, reduction in mechanical strain, and enhanced performance, validating the effectiveness of integrating human-machine engineering and bionics in wearable design.

Comparative analysis of hand dynamometer measurements across different arm positions: implications for rehabilitation and functional assessment

Background and Study Aim. Grip strength is a crucial measure of human physical capability, affecting activities from daily tasks to athletic performance. Variations in arm position during grip strength measurement may influence the results, which has significant implications for both rehabilitation and functional assessment. This study explores the impact of different arm positions on grip strength to enhance understanding of human biomechanics and inform rehabilitation and sports training practices. Material and Methods. Forty right-handed male volunteers (mean age 18.27 ± 0.90 years) participated in the study. Grip strength was measured using a CAMRY Model: EH101 hand dynamometer. Measurements were taken across four arm positions: seated with elbow extension, 90-degree elbow flexion, 90-degree elbow flexion with pronation, and 90-degree elbow flexion with supination. Each position was tested three times. The highest recorded value for each position was used for analysis. Results. The dominant right hand exhibited higher grip strength across all positions compared to the non-dominant left hand. Significant differences were noted, with the greatest grip strength in the extension position. Statistical analysis using paired t-tests indicated significant differences (p < 0.001) between the right and left hands across all positions. Pearson correlation coefficients highlighted strong relationships between different arm positions. Multiple linear regression analysis showed significant predictors of grip strength variability based on arm position, age, and BMI. Conclusions. Arm position significantly influences grip strength performance, underscoring the importance of standardized positioning in ergonomics. Standardizing arm position can optimize performance and mitigate injury risks in activities requiring robust grip strength. These findings have practical implications for rehabilitation protocols, sports training programs, and ergonomic assessments. The results emphasize the need for consistency in grip strength evaluations to ensure accurate and reliable results.

Clinical application of myofascial therapy in the treatment of postpartum pain-related functional disorders: A review.

During pregnancy, fetal growth could lead to changes in human biomechanics. If postpartum recovery was not properly managed, it could be exacerbated, resulting in myofascial system disorders and various functional impairments. Among them, pain-related functional disorders were an important issue affecting quality of life in postpartum women. The pathogenesis of these disorders remained unclear but it was primarily associated with changes in biomechanics, the endocrine system, and nervous function. However, postpartum pain-related dysfunction had been considered a normal physiological response to childbirth, leading to a lack of attention. Therefore, many postpartum women failed to receive timely, effective, and standardized treatment, hindering their ability to reintegrate into family and society, and causing severe damage to their physical and mental health. In clinical practice, myofascial therapy could effectively alleviate postpartum pain and muscle spasms, improve excessive tension injuries in myofascial, and had a good therapeutic effect on postpartum pain-related functional disorders. The mechanism of myofascial therapy involved improving core muscle strength, restoring normal body alignment, and promoting the remodeling of myofascial mechanical structures. This article explored the positive effects of myofascial therapy on postpartum pain-related functional disorders from a biomechanical perspective, aiming to provide diverse treatment approaches for clinical practitioners.

Unveiling human biomechanics: insights into lower limb responses to disturbances that can trigger a fall.

Slip-related falls are a significant concern, particularly for vulnerable populations such as the elderly and individuals with gait disorders, necessitating effective preventive measures. This manuscript presents a biomechanical study of how the lower limbs react to perturbations that can trigger a slip-like fall, with the ultimate goal of identifying target specifications for developing a wearable robotic system for slip-like fall prevention. Our analysis provides a comprehensive understanding of the natural human biomechanical response to slip perturbations in both slipping and trailing legs, by innovatively collecting parameters from both the sagittal and frontal plane since both play pivotal roles in maintaining stability and preventing falls and thus provide new insights to fall prevention. We investigated various external factors, including gait speed, surface inclination, slipping foot, and perturbation intensity, while collecting diverse data sets encompassing kinematic, spatiotemporal parameters, electromyographic data, as well as torque, range of motion, rotations per minute, detection, and actuation times. The biomechanical response to slip-like perturbations by the hips, knees, and ankles of the slipping leg was characterized by extension, flexion, and plantarflexion moments, respectively. In the trailing leg, responses included hip flexion, knee extension, and ankle plantarflexion. Additionally, these responses were influenced by gait speed, surface inclination, and perturbation intensity. Our study identified target range of motion parameters of 85.19°, 106.34°, and 95.23° for the hips, knees, and ankles, respectively. Furthermore, rotations per minute values ranged from 17.85 to 51.10 for the hip, 21.73 to 63.80 for the knee, and 17.52 to 57.14 for the ankle joints. Finally, flexion/extension torque values were estimated as -3.05 to 3.22 Nm/kg for the hip, -1.70 to 2.34 Nm/kg for the knee, and -2.21 to 0.90 Nm/kg for the ankle joints. This study contributes valuable insights into the biomechanical aspects of slip-like fall prevention and informs the development of wearable robotic systems to enhance safety in vulnerable populations.

A CROSS-SECTIONAL CADAVERIC STUDY OF THE PREVALENCE AND MORPHOMETRY OF PSOAS MINOR MUSCLE IN WESTERN MAHARASHTRA

Introduction:The Psoas minor muscle is a long, elongated, spindle-shaped muscle thatis rarelypresent in the human body. Despite its relatively minor role in human biomechanics, understanding its prevalence and morphology can be crucial in certain surgical and diagnostic contexts. Aim:The primary aim of this cross-sectional cadaveric study is to investigate the prevalence and describe the morphometry of the Psoas minor muscle in a population from western Maharashtra. Materials and Methods:63 well-preservedformalin-fixed and soft-embalmed human cadavers were examined during routine dissection. The prevalence, sexual dimorphism, morphology, morphometry, and laterality of Psoas minor muscle were assessed.Digital vernier calipers and tape measure were used to measure the psoas minor muscle morphometry. Result:The study reveals a prevalence rate of 33.33% for the Psoas minor muscle in the studied population. The muscle was present in 21 cadavers out of 63 cadavers. It was bilateral in 17.46% (11/63) cadavers and unilateral in 15.87% (10/63) cadavers. In all the examined cases muscle took origin from a T12-L1 vertebra, and was distally connected to the iliopubic eminence.The muscle was found unilaterally in 05 males and 05 female cadavers, and bilaterally in 07 males and 04 female cadavers. Conclusion:The study provides valuable insights into the presence and anatomical characteristics of the Psoas minor muscle among the population of Western Maharashtra. The prevalence as well as morphometry and morphology of this muscle is of significant academic interest for anatomists, surgeons, radiologists, kinesiologists, and physiotherapists for diagnostic purposes.

Bilateral Back Extensor Exosuit for multidimensional assistance and prevention of spinal injuries.

Lumbar spine injuries resulting from heavy or repetitive lifting remain a prevalent concern in workplaces. Back-support devices have been developed to mitigate these injuries by aiding workers during lifting tasks. However, existing devices often fall short in providing multidimensional force assistance for asymmetric lifting, an essential feature for practical workplace use. In addition, validation of device safety across the entire human spine has been lacking. This paper introduces the Bilateral Back Extensor Exosuit (BBEX), a robotic back-support device designed to address both functionality and safety concerns. The design of the BBEX draws inspiration from the anatomical characteristics of the human spine and back extensor muscles. Using a multi-degree-of-freedom architecture and serially connected linear actuators, the device's components are strategically arranged to closely mimic the biomechanics of the human spine and back extensor muscles. To establish the efficacy and safety of the BBEX, a series of experiments with human participants was conducted. Eleven healthy male participants engaged in symmetric and asymmetric lifting tasks while wearing the BBEX. The results confirm the ability of the BBEX to provide effective multidimensional force assistance. Moreover, comprehensive safety validation was achieved through analyses of muscle fatigue in the upper and the lower erector spinae muscles, as well as mechanical loading on spinal joints during both lifting scenarios. By seamlessly integrating functionality inspired by human biomechanics with a focus on safety, this study offers a promising solution to address the persistent challenge of preventing lumbar spine injuries in demanding work environments.

Challenges and Opportunities in Navigating the Intersection of AI and Ergonomics in the Indian Market

The integration of Artificial Intelligence (AI) with ergonomics is revolutionizing workplace design and efficiency. AIdriven systems analyze human biomechanics and task repetition, providing data to optimize workspaces and minimize musculoskeletal disorders (MSDs). In manufacturing, AI-powered automation reduces physical strain and employs predictive analytics to preempt ergonomic issues. The IT sector benefits from AI-enhanced workstation optimization, especially in remote setups. Healthcare uses AI to refine equipment design and reduce strain through task automation. Construction leverages AI for hazard mitigation and efficient task scheduling. Challenges include high costs, limited expertise, cultural resistance, and infrastructure constraints. Overcoming these requires targeted incentives, education, and scalable solutions. Careful integration is crucial to address new ergonomic risks and ensure AI complements human roles, particularly in the Indian context.

Nonlinearity analysis of sit-to-stand and its application

The examination of human biomechanics, particularly the sit-to-stand transition, has been a focal point of research for numerous years, utilizing mathematical models of the musculoskeletal structure and motion analysis. However, researchers and scientists have encountered substantial challenges attributable to the distributed, nonlinear, and time-varying nature of this phenomenon, characterized by numerous degrees of freedom and redundancy at various levels. Conventional biomechanical assessments of human movement typically rely on linear mathematical approaches, which, while advantageous in various scenarios, often inadequately capture the predominantly nonlinear characteristics inherent in human systems. As a consequence, there has been a growing recognition of the limitations of linear methods, leading to an increased adoption of nonlinear analytical techniques rooted in a dynamical systems approach in contemporary research. Notwithstanding this trend, there exists a conspicuous dearth of a comprehensive review paper that meticulously scrutinizes these nonlinear methods and their applications across the spectrum from modelling to rehabilitation. This mini-review aims to address this gap by highlighting recent advancements in nonlinear methodologies. These methodologies have demonstrated the potential to enhance the efficacy of interventions for individuals with sit-to-stand disorders, encompassing the design of intelligent rehabilitation devices, mitigating fall risks, and facilitating early patient classification.

A Bipedal Walking Model Considering Trunk Pitch Angle for Estimating the Influence of Suspension Load on Human Biomechanics.

Suspended loads have been shown to improve loaded-walking economy. Establishing a biped walking model with dynamic trunk pitch angles can provide more comprehensive estimates of the human biomechanical response under suspended loads. We developed the trunk-load- hip dynamics, modified the spring-loaded-inverted-pendulum (SLIP) model, and optimized the loaded-walking pattern for minimal energetic cost. 9 subjects participated in experiments using a powered backpack to validate the model's performance, conducting two trials: Load-Suspended (LS) and Load-Locked (LL). The averaged correlation coefficient of simulated and experimental hip trajectory, vertical and horizontal GRFs, and individual leg mechanical (ILM) powers are 0.96, 0.97, 0.93, and 0.81, respectively. The RMS error between simulated and experimental peaks of vertical GRFs, braking peaks of horizontal GRFs, and energetic costs was under 10%. Simulation also provides observation on the effect of suspended load on dynamic trunk pitch angles and torques, and leg stiffness. Both the simulation and experiment demonstrated the advantages of LS in reducing GRFs and energetic cost. Additionally, the simulation shows the peaks of trunk flexion and extension torque are reduced by 34.77% (p<0.05) and 37.88% (p<0.05) in LS. The model effectively estimates hip trajectory, vertical and horizontal GRFs, ILM powers, and energetic cost, and provides observations on trunk behavior under different load conditions. The model also supports the advantages of suspension load. Appropriate models could comprehensively reveal the mechanism between the mechanical systems and human biomechanics responses, guide the design of carrying load devices, and provide rapid evaluation of its effects.

The real rotational capacity of the human joints - the muscular and gravitational torques and the foot as a platform

Purpose The purpose was to answer: What is the relationship between torques acting on the human body? How does the triceps calf muscle balance the weight of a tilted body? What is the foot's role in the titling body? Methods Two research models were developed. Model 1 - The one-sided lever system consists of a flat bar with, an axis of rotation, used to determine the weight and torque at a given point on it. Model 2 - The two-sided lever system consists of a flat bar imitating a tilted body counteracted by the Achilles tendon, and a platform imitating a foot. The centre of gravity was determined without considering "the foot". Results When the centre of gravity of the human body tilts, the foot does not participate in the tilt of the rest of the body, because it tilts on the axis of rotation of the upper ankle joint, and not on the plantar side of the foot. The further the point of gravity is from the axis of rotation, the smaller the weight, but the moments of gravity are the same. The apparent weight loss when lifting it with one-sided support (getting up from a squatting position) is a real decrease in the gravitational moment and the lifting moment counteracting it. Conclusions In analysing human biomechanics, focusing on real rotational force (not only the forces of muscle and gravity) is necessary (Muscle moments balancing gravitational moments). The research may help develop effective rehabilitation methods, surgical procedures, and sports training.

A human lower-limb biomechanics and wearable sensors dataset during cyclic and non-cyclic activities

Tasks of daily living are often sporadic, highly variable, and asymmetric. Analyzing these real-world non-cyclic activities is integral for expanding the applicability of exoskeletons, protheses, wearable sensing, and activity classification to real life, and could provide new insights into human biomechanics. Yet, currently available biomechanics datasets focus on either highly consistent, continuous, and symmetric activities, such as walking and running, or only a single specific non-cyclic task. To capture a more holistic picture of lower limb movements in everyday life, we collected data from 12 participants performing 20 non-cyclic activities (e.g. sit-to-stand, jumping, squatting, lunging, cutting) as well as 11 cyclic activities (e.g. walking, running) while kinematics (motion capture and IMUs), kinetics (force plates), and electromyography (EMG) were collected. This dataset provides normative biomechanics for a highly diverse range of activities and common tasks from a consistent set of participants and sensors.

The existing motion capture technologies and their application

Motion Capture technology refers to the technology of recording and processing the actions of people or other objects, and generating corresponding virtual asset action animations. It has been widely used in our daily life. Virtual characters like Hulk, Gollm, and Avatar were all built based on the technology. It can also be applied to sports analysis, human biomechanics, automotive, virtual reality, etc, showing its huge application prospects. Specifically, 3D Motion Capture Market was forecast to reach $270.9 million by 2026 suggested by industry ARC. To help readers get familiar with the field without much background knowledge, this paper reviews the origin of the motion capture technology, the way motion capture technology was realized and the mainstream methodologies of capturing motion. This paper provides the reader with some existing applications of motion capture technology in different fields so that the reader can understand the importance of the technique. Readers can also get some insight into what future studies may be focused on and if there is any promotion of the motion-capturing methods.

Study on Human Motion Energy Harvesting Devices: A Review

With the increasing utilization of portable electronic devices and wearable technologies, the field of human motion energy harvesting has gained significant attention. These devices have the potential to efficiently convert the mechanical energy generated by human motion into electrical energy, enabling a continuous power supply for low-power devices. This paper provides an overview of the fundamental principles underlying various energy harvesting modes, including friction-based, electromagnetic, and piezoelectric mechanisms, and categorizes existing energy harvesting devices accordingly. Furthermore, this study conducts a comprehensive analysis of key techniques in energy harvesting, such as mode selection, efficiency enhancement, miniaturized design of devices, and evaluation of energy harvesting experiments. It also compares the distinct characteristics of different energy harvesting modes. Finally, the paper summarizes the challenges faced by these devices in terms of integrating human biomechanics, achieving higher energy harvesting efficiencies, facilitating micro-miniaturization, enabling composite designs, and exploring broader applications. Moreover, it offers insights into the future development of human motion energy harvesting technology, laying a theoretical framework and providing a reference for future research endeavors in this field.

Biomechanical Properties and Mechanotransduction of Skeletal Muscles as The Basis for The Use of Myofascial Osteopathic Techniques

Skeletal muscles are an important link in human biomechanics. Every movement depends on muscle strength and is important for maintaining health and quality of life. Mechanical loads on the human body directly depend on the state of muscle tissue, so it is necessary to understand the cellular composition and regulation of the tissue responsible for the processes of mechanotransduction . This, in turn, makes it possible to develop methods of effective manual intervention in complex rehabilitation for patients with dysfunctions of the musculoskeletal system. This review describes the molecular basis of mechanotransduction in muscle tissue.

Interday Reliability of Upper-limb Geometric MyoPassivity Map for Physical Human-Robot Interaction.

The value of intrinsic energetic behavior of human biomechanics has recently been recognized and exploited in physical human-robot interaction (pHRI). The authors have recently proposed the concept of "Biomechanical Excess of Passivity," based on nonlinear control theory, to construct a user-specific energetic map. The map would assess the behavior of the upper-limb in absorbing the kinesthetic energy when interacting with robots. Integrating such knowledge into the design of pHRI stabilizers can reduce the conservatism of the control by unleashing hidden energy reservoirs indicating a less conservative margin of stability. The outcome would enhance the system's performance, such as rendering kinesthetic transparency of (tele)haptics systems. However, current methods require an offline data-driven identification procedure prior to each operation to estimate the energetic map of human biomechanics. This can be time-consuming and challenge users susceptible to fatigue. In this study, for the first time, we investigate the interday reliability of upper-limb passivity maps in a sample of five healthy subjects. Our statistical analyses indicate that the identified passivity map is highly reliable in estimating the expected energetic behavior based on Intraclass correlation coefficient analysis (conducted on different days and with various interactions). The results illustrate that a one-shot estimate is a reliable measure to be used repeatedly in biomechanics-aware pHRI stabilization, enhancing practicality in real-life scenarios.

Markerless motion capture estimates of lower extremity kinematics and kinetics are comparable to marker-based across 8 movements

Motion analysis is essential for assessing in-vivo human biomechanics. Marker-based motion capture is the standard to analyze human motion, but the inherent inaccuracy and practical challenges limit its utility in large-scale and real-world applications. Markerless motion capture has shown promise to overcome these practical barriers. However, its fidelity in quantifying joint kinematics and kinetics has not been verified across multiple common human movements. In this study, we concurrently captured marker-based and markerless motion data on 10 healthy study participants performing 8 daily living and exercise movements. We calculated the correlation (Rxy) and root-mean-square difference (RMSD) between markerless and marker-based estimates of ankle dorsi-plantarflexion, knee flexion, and three-dimensional hip kinematics (angles) and kinetics (moments) during each movement. Estimates from markerless motion capture matched closely with marker-based in ankle and knee joint angles (Rxy ≥ 0.877, RMSD ≤ 5.9°) and moments (Rxy ≥ 0.934, RMSD ≤ 2.66 % height × weight). High outcome comparability means the practical benefits of markerless motion capture can simplify experiments and facilitate large-scale analyses. Hip angles and moments demonstrated more differences between the two systems (RMSD: 6.7–15.9° and up to 7.15 % height × weight), especially during rapid movements such as running. Markerless motion capture appears to improve the accuracy of hip-related measures, yet more research is needed for validation. We encourage the biomechanics community to continue verifying, validating, and establishing best practices for markerless motion capture, which holds exciting potential to advance collaborative biomechanical research and expand real-world assessments needed for clinical translation.

Closed-Chain Inverse Dynamics for the Biomechanical Analysis of Manual Material Handling Tasks through a Deep Learning Assisted Wearable Sensor Network.

Despite the automatization of many industrial and logistics processes, human workers are still often involved in the manual handling of loads. These activities lead to many work-related disorders that reduce the quality of life and the productivity of aged workers. A biomechanical analysis of such activities is the basis for a detailed estimation of the biomechanical overload, thus enabling focused prevention actions. Thanks to wearable sensor networks, it is now possible to analyze human biomechanics by an inverse dynamics approach in ecological conditions. The purposes of this study are the conceptualization, formulation, and implementation of a deep learning-assisted fully wearable sensor system for an online evaluation of the biomechanical effort that an operator exerts during a manual material handling task. In this paper, we show a novel, computationally efficient algorithm, implemented in ROS, to analyze the biomechanics of the human musculoskeletal systems by an inverse dynamics approach. We also propose a method for estimating the load and its distribution, relying on an egocentric camera and deep learning-based object recognition. This method is suitable for objects of known weight, as is often the case in logistics. Kinematic data, along with foot contact information, are provided by a fully wearable sensor network composed of inertial measurement units. The results show good accuracy and robustness of the system for object detection and grasp recognition, thus providing reliable load estimation for a high-impact field such as logistics. The outcome of the biomechanical analysis is consistent with the literature. However, improvements in gait segmentation are necessary to reduce discontinuities in the estimated lower limb articular wrenches.

Robotic Information System (RIS): Design of Humanoid Robot’s Head Based on Human Biomechanics

Robotic Information System (RIS) is a new information system architecture that provides data, information processing and services for users in a wide geographical space based on intelligent robots. The front end of the RIS is a humanoid robot head that interacts with users by different means to provide different services. Developing a robot which is similar to a human shape, function and socially accepted by human beings was and is still a challenging subject. Arslan is a new humanoid robot head that has been designed to be close to real human skeletal structure, where its physical structure is designed to be identical to the real human skull, jaw and the nick vertebrae. In order to develop a high-quality and low-cost system, Arslan has a smart mechanism that is controlled by 16 servo motors in order to control its nick, jaw, eyes and facial expression, which have been located according to analysis of human biomechanics. Arslan’s nick mechanism allows one side axial rotation of 41° and flexion/extension of 45°, mandible rotation around the hinge axis of 6 degrees, its eyes can rotate around their axis of motion with Adduction 19°, Abduction 34°, Supraduction (elevation) 0° and Infraduction (depression) 20°. The distance between the upper and the lower eyelid of Arslan can range from 0 up to 17 mm to cover different expressions. Also, it is equipped with devices for motion, vision, audition, smelling, and speech. It also can recognize its head tilting and is capable of maintaining its eyes' direction constantly during head motion