Advancing Circus Biomechanics and Physiology Research with Wearable Technology: Challenges and Recommendations

Abstract

Circus athletes represent a unique population of performers engaging in highly demanding physical activities, yet they remain underrepresented in scientific research. This paper aims to address this gap by exploring the challenges and making recommendations in applying biomechanics and exercise physiology instruments to understand circus athlete movements. Laboratory-based tools such as motion capture technology, force platforms, and metabolic carts offer valuable insights into movement patterns and physiological responses. The growth of wearable technology, including smart garments, inertial measurement units, and Global Positioning System (GPS) devices, has led to opportunities to gather data to quantify the dynamic movements characteristic of circus acts. This paper discusses the capabilities of these devices, emphasizing the importance of selecting appropriate technology tailored to the specific demands of circus performances. By understanding the biomechanics and physiological demands of various circus movements, researchers can develop targeted training and injury prevention programs, ultimately supporting the health and performance of circus athletes. This paper underscores the need for comprehensive, evidence-based strategies to ensure the well-being and success of these extraordinary performers.

1. Introduction

Circus athletes represent a unique and diverse population of performers who engage in a wide range of physically demanding activities, from aerial acrobatics to ground-based acts such as juggling and contortion. Despite their extraordinary skills and the intense physical demands of their performances, circus athletes have received relatively little attention in the scientific literature compared to other athletic populations. This gap in research is concerning, as circus athletes face unique physiological and psychological challenges that warrant specialized study.

McBlaine and Davies [1] conducted a survey of students participating in an instructor-led aerial arts classes. It was reported that there was a self-reported injury rate of 13.70 injuries per 1000 class-hours. Furthermore, it was reported that there were 4.13 injuries per 1000 class-hours for which subjects self-reported seeking some form of medical attention. These observations align with the injury data from professional circus companies and training centers that report a rate of reported injuries between 7.37 and 9.7 injuries per 1000 athletic exposures, or performances [2,3,4,5]. Most injuries in these studies involve the shoulders, spine, knees, and ankles [6,7]. Additionally, these issues are not uncommon, with most artists in these studies experiencing at least one incident that required medical attention. Nearly 40% of artists reported having to miss or modify at least one performance as a result of their injury [5].

Studies on pre-professional circus artists found similar results with the most common injuries involving the shoulders, ankles, and knees [4,8,9,10]. Describing the types of injuries and rate of injuries is an important aspect of understanding injury mechanisms and important in developing evidence-based return-to-play criteria for artists. For example, Greenspan and Stuckey [11] developed physical profile normative values with the goal of having objective data to guide screening for readiness, return to performance, and/or develop strength and conditioning programs for artists. Despite that important work, however, there is a paucity of data regarding specific injury diagnoses circus artists suffer from as well as a lack of data linking specific disciplines with specific diagnoses. That being said, these injury data highlight the importance of understanding the specific needs and conditions of specialized athletic groups.

The paucity of empirical data quantifying circus movements emphasizes that there is an urgent need to explore the various aspects of circus athletics through a scientific lens. That being said, there is a wealth of empirical data quantifying gymnastic movements (see reviews: [12,13,14]) as well as other sport acrobatic movements such as Hip Hop Dance sequences [15], trampoline movements [16], and cheerleading [17]. Much of this type of research is focused on competition sport [18] where movements are scored or judged, whereas circus movements are performed as part of an entertainment show. Nevertheless, the research in these areas can be used as a foundation for understanding circus movements. However, a limitation of research in this area is that it is largely based upon laboratory-based measurements [14]. With the growth of the wearable technology business sector, there is access to instruments that can be used to study circus movements that are unique to gymnastics and in a way that measurements can be taken in unique performance environments.

Circus athletes often perform under conditions that combine extreme physical exertion with elements of artistry and entertainment, requiring not only peak physical fitness but also exceptional mental resilience. The physical demands include repetitive high-impact activities, sustained isometric contractions, and complex motor coordination, all performed under the scrutiny of live audiences, which adds an additional layer of psychological stress [19]. These factors collectively contribute to the risk of overuse injuries, acute trauma, and psychological burnout. However, the lack of empirical data on the specific demands and injury profiles of circus athletes means that current training and rehabilitation programs may not be adequately addressing their needs.

To bridge this gap, it is essential to conduct multidisciplinary research that encompasses areas such as biomechanics, physiology, sports psychology, nutrition, and injury epidemiology specifically tailored to circus performers. Such research should aim to identify the common types of injuries and their mechanisms, understand the physiological adaptations required for various circus acts, and explore the psychological strategies that can enhance performance and resilience. Moreover, studying circus athletes can provide valuable insights that may be applicable to other performing arts and physically demanding professions.

The emergence of the Circus: Arts Life and Sciences journal (first volume published in 2022) and Circus Arts Research Platform (launched in 2018) are examples of a growing body of research on circus movements while also emphasizing the need for circus-focused publications and collaborations. Contemporary circus-focused research can be built on the foundation of gymnastics research. For example, Cossin, Bergeron-Parenteau, and Ross [20] instrumented the riggings of several different apparatuses in order to measure forces during different movements. This work aligns with gymnastics work on still rings conducted but provides unique information applied to the circus performer who complete non-traditional movements that would not be seen in a gymnastic event [21]. Identifying forces applied to circus equipment leads to a better understanding of equipment design as well as the forces the performer applies and is subject to.

To effectively address the unique needs of circus athletes, it is crucial to apply the scientific method to understanding the biomechanics and physiological responses during circus movements. This approach involves systematically observing and analyzing the complex movements performed by circus athletes, formulating hypotheses about the biomechanical and physiological demands of these activities, and conducting experiments to test these hypotheses. Through controlled studies, researchers can identify the specific forces exerted on the body during different circus acts, the muscle groups most heavily engaged, and the physiological responses to these intense activities.

Injury prevention strategies as well as training programs for skill development can be informed by this type of comprehensive biomechanical and physiological understanding. For instance, identifying the specific movements and activities that pose the highest injury risks allows for targeted interventions, such as strength training programs to support vulnerable joints or flexibility exercises to enhance range of motion. Additionally, incorporating recovery protocols and monitoring techniques, such as wearable technology to track physical load and recovery status, can help manage the overall health and well-being of circus athletes. There is a foundation of information from the gymnastics perspective (e.g., [12]); however, it is important to recognize that circus movements are unique in that they extend beyond movements that would be used in gymnastic competitions as well as the performance environment. For example, circus type shows may have multiple performers synchronizing movements, the performers may be wearing a unique costume and may be performing under changing lighting and music conditions.

The purpose of this paper is to discuss some of the tools available that can be used to conduct a comprehensive biomechanical and/or physiological understanding of circus movements. We believe that understanding the tools available will lead to specific research questions that will lead to developing targeted interventions and training programs for circus athletes and thereby enhancing performance and reducing injury risks. The emphasis in this paper was on the performing arts category of circus artist movements that were not part of competitive sports. As such, key search terms were combinations of circus, movements, kinematics, kinetics, and muscle activity.

2. Types of Instruments

2.1. Laboratory-Based Tools

Biomechanical laboratories are typically equipped with tools such as motion capture technology and force platforms. These tools can provide detailed insights into the movement patterns and forces experienced by circus athletes during certain types of movements. A challenge, however, of conducting movement analyses in the laboratory is that camera-based motion capture systems have a limited volume of space that a movement can occur in for the analysis to be accurate. Furthermore, most laboratory-based camera systems can operate with only a single artist at a time. Force platforms are typically fixed to the floor and are stiff surfaces that limit the types of movements that can be adequately studied. Nevertheless, a biomechanical analysis in a laboratory environment can be conducted on some circus movements or, minimally, some components of circus movements. Examining parameters such as joint angles and ground reaction forces during the entire movement or a component of a movement, researchers can identify potential risk factors for injury.

Likewise, exercise physiology laboratories are typically equipped with tools such as metabolic carts, which measure the rate of oxygen consumed and carbon dioxide exhaled during exercise. This information is valuable to understand exercise intensity as well as the metabolic processes involved in certain movements. A challenge with a laboratory-based metabolic cart is that the performer would need to wear a mask which has a tube connected to a computer. The air that the performer inhales and exhales can then be analyzed through specific computer components. Using this type of equipment while running on a treadmill or cycling on a stationary bike can yield important metabolic information about a performer’s metabolic capacity. However, this type of instrumentation would not be able to be used during most circus movements since the mask–tube–computer equipment would interfere with the movements.

2.2. Wearable Technology for Biomechanical and Physiological Assessment

Recent advancements in wearable technology offer powerful tools for conducting biomechanical and physiological assessments of circus movements. These devices often have the capability to provide real-time data that can provide immediate feedback to circus athletes and/or coaches and trainers. Furthermore, wearable technology devices are often suitable for wearing during complex circus movements. The end goal of using these devices is to collect information that can enhance understanding of the physical demands placed on circus athletes and inform injury prevention strategies.

The validity and reliability of these devices are crucial for ensuring accurate data collection and meaningful insights. Validity refers to how accurately a device measures what it is intended to measure. Validity varies depending on the specific wearable, the type of activity being monitored, and procedures to assess validity. Nevertheless, according to review conducted by Bunn et al. [22], wearable devices tend to show high validity in measuring steps and heart rate, although some devices may underestimate these metrics, particularly at higher intensities of activity.

Reliability pertains to the consistency of the measurements obtained from the device across different trials and conditions. Reliable devices produce similar results under consistent conditions over repeated tests. The systematic review by Bunn et al. [22] highlighted the importance of using standardized protocols to assess the reliability of wearable technology [22]. Bunn et al. [22] reported that while some devices demonstrate high test–retest reliability, others exhibit variability due to factors like sensor placement, movement artifacts, and device calibration.

Bunn et al. [22] also emphasized the necessity for continuous updates and evaluations of wearable devices due to the rapid advancements in technology and frequent release of new models. They recommended that future research should include comprehensive protocols that assess both the validity and reliability of wearable devices using multiple methods, such as Bland–Altman plots, correlation techniques, and mean absolute percent error calculations. Unfortunately, the validity and reliability of wearable technology is often left to the user to determine. However, in some cases, manufacturers list references that have been published demonstrating validity and reliability of devices.

In the next section of the paper, a variety of wearable devices that might be suitable for circus movements are presented.

2.3. Smart Garments with Inertial Measurement Units

Smart garments are often equipped with inertial measurement units (IMUs) and can provide a detailed 3D analysis of movement patterns. They are capable of capturing a wide range of motions in various environments, making them ideal for dynamic and complex circus movements. These garments are also relatively non-intrusive, allowing for natural performance during data collection.

Smart garments are often expensive, and it is important to have a variety of sizes of garments that fit a variety of sized circus athletes. When using IMUs, it is important that the sensors are tightly secured to the body (via tight fitting clothing) to avoid excessive movement artifacts. Furthermore, it is important to know how data will be processed. Many smart garments are limited in that the data are processed via proprietary software and it is not possible to export raw data to process via laboratory specific processing routines. Along with that, it may be difficult to isolate the data recorded during specific movements if the proprietary software is not capable of trimming data sets. Furthermore, using proprietary software may lead to time consuming data processing if the software is mostly designed to provide aggregate data or presenting data visually (e.g., graphically) only, for example.

The advantage of using proprietary software is that information is generally presented in a user-friendly graphical interface. However, if the smart garments are used for research purposes, the user must have the experience and expertise to critically evaluate the information provided since the user is not always aware of the processing steps that are embedded in the proprietary software.

2.4. Heart Rate Monitors

Heart rate monitors provide real-time data on heart rhythms and can provide insight for understanding the physiological load during performances. They are widely used, relatively affordable, and easy to integrate into training routines. Continuous heart rate monitoring can help in designing appropriate training intensities and recovery protocols. Heart rate monitors consist of transmitting and receiving units. The transmitting unit is typically worn on a chest strap. This is a very common type of transmitter to use for a wide range of exercises. However, it is important to know that there are a variety of other transmitting units that can be worn on the finger, arm, or even temple portion of the head. However, the use of optical heart rate sensors needs to be carefully evaluated since the measurement of heart rate can vary between devices [22] and depending on where the sensor is placed and the intensity of exercise [23]. The location of the transmitting unit should be considered based upon the type of circus movement that will be researched. Given the dynamic nature of many circus movements, heart rate may not be the best tool to quantify physiology. That is, many movements require the activation of both the aerobic and anaerobic metabolic pathways. As such, heart rate alone will not be an adequate tool to describe the physiology of many circus movements.

2.5. Rate of Oxygen Consumption

Recent advancements in portable metabolic carts have also contributed to the field of wearable technology for physiological assessment. Traditional metabolic carts, often limited to laboratory settings due to their size and need for controlled environments, have evolved into lightweight, wearable systems that allow for real-time metabolic monitoring in dynamic performance settings. These portable devices enable researchers to measure rate of oxygen consumption (VO₂), rate of carbon dioxide production (VCO₂), and energy expenditure during circus performances and/or practices. The ability to track metabolic demands in real-world conditions can provide a more comprehensive understanding of the physiological stresses associated with different circus disciplines, allowing for better training strategies, workload management, and injury prevention measures. However, most portable systems require carrying a data logger (in a backpack) and a mask needs to be worn by the user. Some circus movements may be too dynamic to use this type of equipment and the costume worn during a performance and/or practice may limit the ability to carry the data logger.

2.6. Core Temperature

In addition to metabolic monitoring, wearable technology has advanced in the measurement of core temperature, an important factor in assessing thermal strain and physiological responses to performance conditions. An effective method for core temperature monitoring is the ingestible core temperature pill, which transmits real-time internal temperature data during dynamic movements as it passes through the gastrointestinal tract. This technique provides accurate data without interfering with movement, making it particularly valuable for circus athletes performing under intense physical exertion and variable environmental conditions.

Another method for assessing core temperature is the use of surface temperature sensors, which are typically placed on the skin or embedded in smart garments. While these sensors provide continuous monitoring and are easy to implement, they may be influenced by external factors such as ambient temperature, humidity, and sweat. Advances in sensor technology have improved their accuracy, allowing researchers to estimate core temperature trends by combining skin temperature data with additional physiological parameters such as heart rate and movement patterns.

2.7. Wearable Muscle Activity Sensors

Some smart garments incorporate sensors that measure muscle activity. Electromyography (EMG) is a specific technique that is used to determine specific information about muscle activity. There are acceptable standards when using EMG (e.g., International Society of ElectroKinesiology (ISEK)). Smart garments that measure muscle activity are generally measurements of a broad surface area vs. a refined EMG technique. There may be some usefulness in having general information about muscle activity; however, it is important to be fully aware that these types of garments provide a general picture of muscle activity and may not meet the EMG standards set forth (e.g., ISEK) when the user is looking to publish data in a peer reviewed manuscript. For example, when using laboratory-based EMG systems, the EMG leads are placed on specific anatomical landmarks. Smart garments with EMG capability may have a more broad placement of a sensor area and if the location of sensing area of the garment relative to muscle location may vary based upon garment fit. Likewise, sample rates of many wearable technologies may not be sufficient to capture the full frequency band of muscle activity.

2.8. Global Positioning System and Activity Trackers

Global positioning system (GPS) devices and activity trackers can monitor movement patterns, distances covered, and overall activity levels. Typically, smart watches have used GPS to quantify parameters such as distance and velocity. However, GPS is one system that falls under the umbrella of Global Navigation Satellite Systems (GNSS). A smart watch that is multi-GNSS indicates that several systems are accessed such as GPS, GLONASS (Russia), Galileo (EU), BeiDou (China), and QZSS (Japan).

Wearable technology that incorporates GNSS (e.g., GPS watches) are useful for quantifying different measurable aspects of outdoor training, activities, and performances such as distance covered, pace, elevation gain, and so forth. These devices are user-friendly and often come with proprietary software for data analysis. However, accuracy is compromised in indoor settings or areas with poor satellite reception.

An alternative tracking device for indoor activities is a Local Positioning System (LPS) [24,25]. The LPS is a technology that quantifies human movement by tracking an individual’s position and motion in a confined area and is operational indoors [25]. These systems measure the distance between transmitters (on the person or object being tracked) and fixed receivers to calculate precise positions in real-time. LPS provides high-resolution data on position, speed, and acceleration, making it valuable for analyzing circus artist movements indoors.

Finally, it is important to note that non-GNSS devices such as activity trackers are built using accelerometers and gyroscopes. They provide information such as step count, time spent moving at different speeds, as well as acceleration information. In general, activity trackers typically offer a generalized overview of physical activity.

This is not an exhaustive list of wearable technology that is available. Furthermore, wearable technology devices are evolving due to miniaturization of instruments, increased computing power, and more sophisticated processing algorithms, for example. Overall, wearable technology has the capability to enhance circus biomechanics and physiology research by enabling real-time, field-based data collection. However, the validity, reliability, and practicality of each device must be carefully considered to ensure meaningful insights into performance optimization and injury prevention.

3. Types of Circus Movements

Circus movement acts encompass a diverse array of performances, each demanding unique physical and artistic skills. These acts can be broadly categorized into aerial acts, ground-based acts, balancing acts, and prop manipulation acts (

Table 1. A description of different categories of artistic movements.

Type of Act	Description
Aerial Acts	Aerial acts involve performances above the ground, requiring strength and flexibility. The primary types of aerial acts include the following: – Aerial Silks: Performers climb, wrap, and drop using long fabric strips, showcasing acrobatic skills, and creating visually stunning displays. – Trapeze: This includes both static and flying trapeze. Static trapeze involves a bar connected by ropes to a frame, where artists perform acrobatic moves. Flying trapeze artists leap from one trapeze bar to a catcher hanging from another, often executing multiple flips or other maneuvers in mid-air. – Aerial Straps: Similarly to aerial silks, but using looped aerial straps, performers showcase their power and control through dynamic movements and holds.
Ground-Based Acts	These acts are performed on the stage or ground level, emphasizing athleticism and coordination: – Acrobatics/Rebound: This includes tumbling, trampoline, teeterboard, and group acrobatics, where performers execute flips, somersaults, and complex balancing acts on the floor or on surfaces designed to increase height. – Contortion: Performers demonstrate extreme flexibility by bending and twisting their bodies into unusual and often seemingly impossible positions. – Hand Balancing: This involves balancing the entire body on one or both hands, often on elevated platforms or objects.
Balancing Acts	Balancing acts focus on maintaining equilibrium on precarious apparatuses, highlighting the performers’ poise and precision: – Tightrope Walking: Artists walk across a thin wire or rope, often performing additional tricks like juggling or acrobatics. – Slackline: Somewhat of a cross between tightrope and trampoline, the line is much wider and less taut, adding an extra challenge due to its dynamic nature. Artists perform bounces and flips to and from their feet, stomach, back, and seat. – Rola Bola: Performers balance on a board placed on top of a rolling cylinder, often stacking multiple boards and cylinders to increase difficulty.
Prop Manipulation Acts	These acts involve manipulating objects in complex and entertaining ways, requiring dexterity and coordination: – Juggling: Artists toss and catch multiple objects such as balls, clubs, rings, or even unconventional items like knives and fire torches. – Diabolo: It is a type of juggling using a spool that is balanced, spun, and tossed on a string tied between two sticks. – Poi Spinning: Performers spin tethered weights in rhythmic patterns, often with lights or fire for added visual effect. – Hula Hooping: This involves spinning hoops around various parts of the body, often incorporating dance and acrobatic elements.

). Example pictures of movements are included in a collage (Figure 1) to give a sense of the dynamic nature of movements. The characteristics of each movement type determine the selection of wearable technology for biomechanical and physiological assessment, influencing data collection on movement efficiency, injury risk, and performance optimization.

Gatewood and Hingson [26] provided a more detailed discussion of the classification systems and emphasized the relational structure of circus disciplines, categorizing acts not only by movement style but also by the apparatus involved and their interconnected nature. For example, trapeze acts share biomechanical similarities with rope acts due to their swinging motions and upper-body engagement, while acrobatic tumbling sequences might overlap with rebounding disciplines like trampoline-based acts. These relationships between movement categories provide an essential framework for understanding how circus performers engage with their environment and the forces acting upon them. There may be a benefit of conducting research that is focused on movement categories vs. the entire circus act.

From a medical standpoint, circus movements can be classified based on biomechanical load, injury risk, and the type of physical stress they impose on the body. Faltus and Richard [27] categorize circus performers into sudden-load performers, non-sudden-load performers, and musicians. Sudden-load performers, such as acrobats, aerialists, and trampoline artists, experience high-impact forces due to sudden changes in velocity and external load, increasing their risk of acute injuries such as fractures and ligamentous injuries. Non-sudden-load performers, including jugglers, clowns, and some dancers, typically experience lower-impact forces but are more prone to overuse injuries affecting the hands, shoulders, and lower back.

Additionally, circus acts impose unique demands on the musculoskeletal system, requiring a distinction between high-flexibility disciplines (e.g., contortion, hand balancing) that stress joint hypermobility and high-strength disciplines (e.g., aerial straps, trapeze) that demand repetitive muscular contractions under significant loads. Each classification informs injury prevention strategies, rehabilitation approaches, and training adaptations, ensuring performers maintain longevity in their careers while minimizing injury risks.

For any classification system, it is important to recognize that each type of circus movement act requires specialized training, coordination, and adaptation to various apparatuses. Additionally, some disciplines cut across multiple categories, highlighting the fluid nature of circus movement classification. Recognizing these intersections is key to improving both performance analysis and injury prevention strategies.

Classifying movements also highlights that it may be necessary to instrument the apparatus in combination with wearable technology worn by the performer. Cossin et al. [20] instrumented circus riggings to measure forces during different acts. For example, it was reported that forces can range from 2.5 times the body weight in duo fixed trapeze to over 7 times the body weight in aerial rope, with tightwire apparatus experiencing forces as high as 15 kN. These insights are clearly essential for rigging design, load-bearing calculations, and improving equipment safety standards but also provide insight in the forces exerted by artists on circus riggings.

Despite this existing knowledge, there remains a significant gap in empirical research focused on the quantification and analysis of the forces involved in the broad range of circus movements. While traditional sports science has made considerable progress in modeling ground reaction forces, joint kinetics, and muscular activation patterns in athletes, relatively little is known about the dynamic loading conditions in circus arts. The variety and complexity of movements—many of which are performed on suspended apparatuses or in non-standard postures—pose challenges to conventional measurement approaches.

To address this gap, it is essential to develop biomechanical models and measurement strategies that reflect the specific force profiles of each act. For example, aerial disciplines such as silks, rope, and straps involve eccentric loading, grip-intensive suspensions, and rapid deceleration, which may contribute to both acute and chronic injuries. Ground-based acrobatics and tumbling acts require precise control of angular momentum and often expose performers to repeated impact forces. Balancing acts on apparatuses such as tightwire or unicycles introduce multi-directional perturbations, challenging neuromuscular control and increasing demands on stabilizing musculature.

Moreover, the forces experienced during partner-based acts—such as hand-to-hand acrobatics or duo trapeze—are influenced not only by the performer’s movement but also by the dynamic interaction between partners. These scenarios present an opportunity to study force transmission across bodies, an area that remains largely unexplored.

Key Points to Consider When Selecting Wearable Technology to Quantify Circus Movements

Selecting appropriate wearable technology for quantifying circus movements is crucial for obtaining accurate and useful data. The unique demands of circus performances require careful consideration of various factors to ensure that the technology used is both effective and practical.

Selecting the right wearable technology for quantifying circus movements involves a balance of accuracy, comfort, durability, data accessibility, cost, and integration capabilities. By carefully considering these factors, researchers and trainers can effectively monitor and enhance the performance and safety of circus athletes. Key points to consider are presented in

Table 2. Key points to consider when selecting wearable technology to quantify some aspects of a circus movement.

Type of Data Required	Different wearable devices provide various types of data, so it is essential to identify the specific metrics needed for research or training goals. Key data types include the following: – Kinematic Data: Information on movement patterns, speed, and acceleration, typically captured by inertial measurement units (IMUs). The technology of markerless camera-based systems has progressed and removes the need to place reflective markers on a performer (which could interfere with movement and/or custom). – Kinetic Data: Force- or pressure-sensing insoles can be placed in the shoe of a performer to measure forces. Some units wireless transmit data to a data logger (e.g., smart phone), which gives the advantage of not having the artist wear a data logger. – Physiological Data: Heart rate, muscle activity, core temperature, and other physiological responses can be measured using heart rate monitors, EMG sensors, ingestible pill, and portable metabolic carts. – Spatial Data: GPS devices or LPS can track metrics such as distance and velocity.
Device Accuracy and Reliability	The accuracy and reliability of the wearable technology are paramount. Consider devices that have been validated for use in dynamic environments similar to circus performances. Factors affecting accuracy include the following: – Sensor Precision: Ensure that sensors can capture detailed and accurate data, especially during rapid and complex movements. – Data Consistency: The device should provide reliable data across multiple uses and varying conditions. – Sample rate: Research-grade instruments facilitate selecting the appropriate instrument sample rate. For example, it is acceptable to use a sample rate of at least 500 Hz for measuring electromyography data. Kinematic data can be recorded as low as 30 Hz but may require a higher sample rate of 200 Hz depending on the research question being asked. Kinetic data (e.g., ground reaction force) are typically collected at 1000 Hz, but the sample rate selected can vary depending on the type of research question asked. When selecting a wearable technology device, it is important to understand the sample rate that the device uses. In many cases, the sample rate may be too low that would justify using the device as a research-grade instrument. However, in that case, there may be some general descriptive information that may be useful.
Comfort and Fit	Circus performers engage in highly dynamic and flexible movements, and typically wear a costume during performance and/or practice making comfort and fit crucial for wearable technology. Important aspects to consider include the following: – Non-Intrusiveness: Devices should not hinder the performer’s range of motion or comfort. Lightweight and flexible wearables are preferred. – Secure Fit: Ensure that the device remains securely in place during intense activity to avoid data inaccuracies due to movement artifacts.
Durability and Battery Life	Wearable devices used in circus performances must withstand rigorous use and have sufficient battery life to cover entire practice sessions or performances: – Robustness: Devices should be durable enough to handle the physical demands of circus acts, including impacts and exposure to sweat. – Battery Efficiency: A long battery life is essential to avoid interruptions during extended performances or training sessions.
Data Accessibility and Processing	The ease of accessing and processing the collected data is a key consideration. Look for features such as the following: – Real-Time Feedback: Devices that provide immediate feedback can be beneficial for adjusting performance techniques on the spot. – Data Export Capabilities: The ability to export raw data for further analysis using specialized software is crucial for detailed biomechanical and physiological studies. – User-Friendly Interface: Intuitive software interfaces help performers and researchers easily interpret and utilize the collected data.
Cost and Availability	Budget constraints and the availability of devices are practical considerations that can influence the choice of wearable technology: – Affordability: While advanced features are desirable, the cost of the device should align with the available budget. If the wearable technology is a garment, multiple sizes and care of washing between users must be considered. – Availability: Ensure that the chosen technology is readily available and supported by the manufacturer for maintenance and troubleshooting.
Integration with Existing Systems	Compatibility with other systems and devices used in training and research can enhance the overall effectiveness of the wearable technology: – Synchronization: The ability to sync data with other monitoring systems or software can provide a comprehensive overview of the performer’s biomechanics and physiology. – Scalability: Consider whether the technology can be scaled to accommodate multiple performers simultaneously if needed.

and in an infographic in Figure 2.

4. Circus Research Using Wearable Technology

Wearable technology has been increasingly used to quantify the biomechanical and physiological demands of circus performances. A notable example is the study by Barker, Burnstein, and Mercer [28], which examined the mechanical characteristics of a trampoline-based circus act using a tri-axial accelerometer. Their study aimed to compare the acceleration profiles of acrobats during training and live performances to better understand workload demands and potential implications for injury prevention and performance management.

Barker et al. [28] equipped seven male acrobats with wearable accelerometers to measure movement patterns during a trampoline act in both training and show environments. The results indicated that training sessions exhibited significantly higher acceleration values than performances, suggesting that artists may engage in more intensive movements during rehearsals. However, perceived exertion was higher during live performances, likely due to increased psychological stress and the necessity for precise synchronization with other performers. This study demonstrated the utility of wearable technology in quantifying track-specific demands and highlighted its potential application for optimizing training loads, reducing injury risks, and supporting artist workload management in circus environments.

The findings from this study align with broader trends in sports science, where wearable devices are used to monitor athlete workload in field sports such as rugby [29] and soccer [30]. These methods provide circus coaches with valuable data to make informed decisions regarding artist training, recovery, and injury prevention strategies. Given the physically demanding nature of circus performances, continued research in this area is crucial to developing evidence-based approaches for supporting the health and longevity of circus athletes.

Building on the kinematic work, Cossin et al. [31] further investigated the relationship between jump height, landing techniques, and the mechanical properties of different teeterboards. Their study analyzed peak landing forces and maximal loading rate among professional acrobats using pressure sensors insoles as well as a 10-camera motion capture. They reported that landing forces were upwards of 13 times the body weight. The peak force was dependent on jump height and were highest when using stiff teeterboards. Additionally, landing technique—qualitatively described through magnitude of knee flexion during landing—influenced impact forces. By using wearable technology in the form of pressure insoles, valuable information regarding the interaction of the acrobat (e.g., landing and jump techniques) and teeterboard design will help aid in training and mitigation of risks associated with high-impact landing movements.

Another approach to quantifying kinematics of a circus movement, Cossin et al. [32] conducted a kinematic analysis of Korean teeterboard acrobatics to understand the dynamic interactions between acrobats and the teeterboard apparatus. Their study utilized a 68-camera motion capture system to identify key variables influencing jump height, with a particular focus on the role of vertical forces exerted during takeoff and landing. The researchers highlighted the significance of maximizing board deflection and ensuring precise timing in leg extension to optimize performance. Their findings underscore the necessity of quantifying forces in circus acts, as proper force distribution is crucial for both performance enhancement and injury prevention. This research provides valuable insights for equipment designers and coaches seeking to refine training techniques and improve apparatus functionality. This type of work would be enhanced by using wearable technology or less intensive camera instrumentation to gather kinematic data.

Another study in the circus biomechanics domain is the work of Helten et al. [33], which introduced a method for classifying trampoline jumps using inertial sensors. Their study focused on developing an automated approach for segmenting and classifying trampoline movements into predefined motion categories, such as pike jumps and somersaults. Since optical motion capture systems have limitations in capturing dynamic and spatially extensive trampoline motions, Helten et al. [33] utilized a small number of inertial sensors attached to athletes’ bodies to gather data on acceleration and angular velocity. To enhance classification accuracy, Helten et al. [33] implemented robust feature representations and class templates capable of handling variations in movement execution across different performers. Their study demonstrated a high classification accuracy even in the presence of substantial stylistic variations among athletes, highlighting the effectiveness of inertial sensors in analyzing aerial movements. Their research underscores the potential of wearable technology to identify movements and phases of movements that can be used for extracting kinematic data for analysis. This could also assist in analyzing muscle activity data if inertial sensor data can be synchronized with muscle activity sensor data.

In line with the work of Helten et al. [33], Zhang et al. [34] developed a finite element model to estimate contact dynamics during trampoline jumping. Their study integrated a musculoskeletal model with a dynamic simulation of a trampoline bed to examine lower extremity joint forces and muscle activation patterns. By coupling finite element modeling with real-world motion data, Zhang et al. [34] were able to assess peak reaction forces experienced during trampoline landings and identify asymmetric loading patterns that contribute to rotational movements. Their findings provide valuable insights into optimizing trampoline performance techniques and mitigating injury risks through targeted strength training and movement adjustments.

By integrating wearable technology into circus biomechanics research, future studies can explore various circus disciplines in more detail, refine workload models, and assess long-term adaptations to training regimens.

5. Future Directions

Future research should focus on developing standardized protocols for applying wearable technologies across the diverse range of circus movements. This includes validating devices in real-world performance settings and ensuring that data can be meaningfully interpreted in relation to performance outcomes and injury mechanisms. Collaborations between researchers, circus institutions, and technology developers will be essential to refine measurement tools and tailor them for the unique demands of circus movements. Additionally, longitudinal studies are needed to track performance metrics, recovery patterns, and injury trends over time. Expanding research to include not only biomechanics and physiology of movements but research in sport psychology and nutrition, for example, is important to further enhance our understanding of circus artist performance and well-being. These efforts will support the development of evidence-based training, safety protocols, and personalized interventions that preserve both artistry and longevity in circus careers.

6. Conclusions

The purpose of this paper was to discuss tools available for conducting a comprehensive biomechanical and/or physiological understanding of circus movements, with an emphasis on wearable technology. As such, we have presented an overview of laboratory-based instruments and wearable devices, including their advantages, limitations, and considerations for use in the unique context of circus performance. We intended to present the information in a way to provide practical guidance for researchers and practitioners seeking to apply these tools in real-world settings. By adopting a comprehensive and multidisciplinary research approach, evidence-based strategies can be developed to support the health, performance, and well-being of these extraordinary performers, ensuring they can continue to captivate audiences while maintaining their physical and mental health.

The application of wearable technology to assess the biomechanics and physiological responses of circus athletes offers a promising avenue for enhancing performance and preventing injuries. Each type of wearable device comes with its own set of advantages and limitations, and the choice of technology should be guided by the specific research objectives and practical considerations of the circus environment. By leveraging these advanced tools, researchers can gain valuable insights into the complex dynamics of circus performances, ultimately supporting the health and success of these extraordinary athletes.