Exoskeletons and Occupational Health Equity

In the workplace, you need your equipment to fit perfectly. Historically, personal protective equipment (PPE) had been developed from measurements taken from male military recruits in the United States during the 1950s to the 1970s [1]. These data do not represent the range of body shapes and sizes in the majority of the modern workforce, as they are based on men who were young, fit, and the majority of whom were white. This has resulted in poorly fitting PPE for women, non-whites, and individuals with body shapes and sizes that may not fall ‘within the range’, i.e. those who are overweight, shorter than 5’5ʺ or taller than 6’. As more women enter occupations such as construction, manufacturing, and logistics management improperly fitting PPE is an especially major challenge [2]. Poorly fitting PPE is particularly problematic because it can prevent equipment from functioning properly, be a safety hazard, and discourage its use by workers [3].

To promote health equity in the workplace, the future design of PPE and technology must account for a wider range of human shapes and sizes to ensure accessibility for all workers. Health equity is when everyone has the opportunity to be as healthy as possible [4]. An example of how health equity can be applied in the workplace is in the emerging area of occupational exoskeletons. Occupational exoskeletons are “wearable devices that augment, enable, assist, and/or enhance physical activity through mechanical interaction with the body.” [5]. They are designed to physically assist workers in reducing their exposure to associated physical demands [6]. There are two major types of exoskeletons: active or powered exoskeletons, which operate by means of electric motors or batteries; and passive or unpowered exoskeletons, which are propelled by human movement [7].

Occupational exoskeleton technologies are rapidly developing and so is the body of evidence regarding their potential effects on workers in diverse applications [8]. It is imperative to assess the critical dimensions and configurations of exoskeletons to make them applicable to and effective for use in a wide range of tasks and to ensure fit, comfort, and usability for a broad set of users of different sizes and body types, genders, and ages [8]. The fit of an exoskeleton is a complex issue. Static assessments of fit that result in a ‘one-size-fits-all’ suit are insufficient [9,10]. Comfortable fitting exoskeleton suits that are adaptable to a variety of body shapes require multivariate or 3-dimensional anthropometric data in the design process [9,10].

Occupational exoskeletons have the potential to reduce the number and associated costs of musculoskeletal injuries in several industries. The use of back assist exoskeletons was found to reduce back muscle activity by 10-44% during handling tasks in laboratory studies [11]. In addition to a reduction in spinal muscle activity, reductions in hip extensor muscle activity by 24%, and neck muscles by 50% were also observed when using a back assist-exoskeleton in laboratory-based tasks [12]. However, the potential benefits of the exoskeleton depend on the posture adopted, the tasks it is used for, and whether it properly fits the user or not [13]. Also, while the benefits are indeed promising, there is the possibility of introducing new risk factors. For example, studies have shown increased chest pressure [13] due to wearing the device.

Many exoskeletons may be designed as ‘unisex’ devices, especially with respect to placement of the exoskeleton components, which may pose a problem to women [10]. Women make up half of the workforce, and any exoskeleton that is designed to fit the entire workforce must fit the female form. Women work in industries and occupations that present many ergonomic hazards and risks for musculoskeletal injuries/illnesses. In 2018, women made up 10% of construction workers, 29% of manufacturing workers, 46% of public administration workers, and 45% of retail workers [14]. Women make up more than 85% of nurse practitioners, registered nurses, licensed practical and vocational nurses, and nursing, psychiatric, and home health aides [14, 15]. Women experience osteoporosis up to four times more than men, 30% of women will have the disease at any given time, and half of women may experience a fracture of the hip, wrist, or vertebrae in their lifetime [16]. In combat, women were injured at more than six-times the rate of their male counterparts, with a significantly higher percentage of these injuries attributable to tasks requiring movement under load [17, 18].

While exoskeletons may be available in more than one size, sizing is only one element of comfort and user acceptance. Back support exoskeletons often have chest pads that may not be comfortable for female employees, and may have proportions between the shoulder width, torso length, and hip width that may be more suited towards male employees [7], leading to poor comfort and low acceptance by women. Poor fitting exoskeleton suits can cause awkward working postures and thus, increase the risk of shoulder/back fatigue or disorders [19]. Poor fit can also discourage use by female employees, making the benefits of this technology less accessible to them.

Within the last two decades, NIOSH researchers have produced much research with more inclusive measurements for PPE. This has included a database for firefighters and firefighter apparatus manufacturers to begin updating their designs of seat belts, fire truck cabs, and PPE. This research was based on a groundbreaking anthropometric study conducted on U.S. firefighters, showing the importance of representative sizing [20, 21]. Recent NIOSH research also revealed that truck drivers’ measurement showed significant differences from truck drivers’ measurements 30 years ago, prompting many in the truck manufacturing industry to redesign truck cabs to better support driver safety [20, 22]. Furthermore, NIOSH research on fall-arrest harness sizing provides practical production information for the harness manufacturing industry to formulate cost-effective harness designs and sizing schemes for diverse populations, especially for women and minorities, to provide the required level of protection, productivity, and comfort [1].

Exoskeleton testing typically involves small sample sizes that may not represent the larger user population sample [23]. Similar to NIOSH’s efforts in producing inclusive measurements for PPE, a larger-scale anthropometry survey of exoskeleton users would be beneficial to exoskeleton manufacturers, users, and safety professionals. Alternatively, experts have suggested using simulation and digital human modeling technologies for assessing the interface between the user and exoskeleton and reducing the test and evaluation burden of using human subjects [24, 25, 26].

Over the past few years, occupational exoskeletons have become widely available and rapidly accepted in a wide range of industries. Exoskeletons have many potential benefits, but they may have just as many unintended consequences. If the exoskeleton does not properly fit the worker, then there may be the possibility of increased injuries. Exoskeleton research is evolving at an exceptional pace. The changing demographics of the workforce need to be taken into consideration to ensure that these technologies are inclusive of the workforce’s diversity and equitably benefit and protect all.

If you have used an exoskeleton in your workplace, please provide your input regarding the following questions in the comment section below:

1. What do you think are some design problems for exoskeletons?
2. Is everyone in your workplace able to benefit from exoskeletons, regardless of their body shape and size?

Lakshmi (Dawn) D. Robertson, Dr.PH, MSPH, ASP, AEP, is an ergonomist in the NIOSH Western States Division.

Laura Syron, PhD, MPH, is an epidemiologist in the NIOSH Western States Division and Assistant Program Coordinator for the Occupational Health Equity Program.

Michael Flynn, MA, is a social scientist in the NIOSH Division of Science Integration and coordinates the Occupational Health Equity Program.

Theodore D. Teske, MA, is a health communication specialist in the NIOSH Western States Division.

Hongwei Hsiao, PhD, is Chief for the Protective Technology Branch in the NIOSH Division of Safety Research.

Ming-Lun (Jack) Lu, PhD, CPE, is a research ergonomist in the NIOSH Division of Field Studies and Engineering and manager of the NIOSH Musculoskeletal Health Cross-Sector Program.

Brian D. Lowe, PhD, CPE, is a research industrial engineer in the NIOSH Division of Field Studies and Engineering.

For More Information

Industrial Exoskeletons

Can exoskeletons reduce musculoskeletal disorders in healthcare workers?

Exoskeletons in construction: will they reduce or create hazards?

Occupational Health Equity

The NIOSH Center for Occupational Robotics Research

References

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