Wearable robotics for the lower limb – Powered Exoskeletons

Wearable robotics for the lower limb – Powered Exoskeletons

An Airborne Crisis on Two Fronts

Robotic technologies are getting more common in the healthcare industry. You can find people that have had surgeries from robotics, and you also hear people using robotics for physical rehabilitation. We live in an era where there is a rapid growth of technology developments and one such technology that has been increasingly catching all the attention are exoskeletons.  

The term exoskeleton comes from the Greek words “exo” meaning external and “skeletos” meaning skeleton. It is a wearable robot or outer structural mechanism with joints that correspond to those of the human body[1]. 

Figure 1: Lower Limb exoskeletons from left: ReWalk, HAL, Ekso GT and Phoenix. (adapted from Bourgeois, S. (2018))[2]

Exoskeletons, especially those for the lower limb, have become increasingly popular in recent years. Gait disorders affect 60% of patients with neurological conditions and generally affects their quality of life. Imagine not being able to walk around the park or go to the grocery store and pick up your favourite cereal on the top shelf.  


Some major advantages of powered exoskeletons for rehabilitation needs are[1][3][4]: 

  • Preventing muscle atrophy 
  • Preventing deterioration of osteoporosis/osteopenia 
  • Reduce energy required to move the primary joints as the load is taken by the exoskeleton 
  • Target specific joints for rehabilitation purposes 
  • Pressure relief 
  • Bowel and bladder improvements  
  • Reduces risk of hypotension 
  • Increase the autonomy of users by allowing independence 
  • Improve physiological state of the user 
  • Reducing spasticity 

Most research on exoskeletons is being carried out on spinal cord injury (SCI) patients. Generally, less than 5% of these populations can ambulate without physical assistance. Walking using an exoskeleton will encourage these patients to engage in physical activity at an intensity that encourages health benefits. These effects also mitigate the independent health risks that are associated with prolonged sitting[5]. 

Using robotics also allow a standardised training session and enables longer training times. Technology for rehabilitation has relieved therapists from mundane repetitive work that is also physically demanding. It allows them to focus on other aspects of individual therapy and care.  


Albeit making significant advances in the past decade, powered exoskeleton technologies still have their shortcomings that are perhaps hindering the rapid adoption of the technology in healthcare. The user-friendliness of the human-robot interaction consisting of the mechanical, control, and feedback mechanisms determines whether the technology is integrated into the clinical setting. 

An average exoskeleton accommodates users of between 150-190cm with a maximum weight limit of 100kg. Most people would be excluded from those criteria alone as being overweight is an arising issue especially for non-ambulatory patients.  

Most exoskeletons are designed to be utilised with elbow crutches. Otherwise, the device will be too heavy and rigid for use during rehabilitation. However, this denies patients of higher-level injuries and those that lack upper limb movements the ability to utilise this technology that will prove beneficial as stated above.  

Because of the need of having supervision and clinical support, most exoskeletons are generally used within clinics and rehabilitation centres. The time taken to don and remove the exoskeleton off also varies but generally needs more than 10 minutes.  

Implications for Research 

The robotics community would greatly benefit from specific policies and guidelines that can speed up the development and adoption of exoskeleton technologies. Exact therapy times for gait training have yet to be decided to achieve optimal outcomes. Future research would need to focus on the optimal training conditions for patients in terms of speed, step length, cadence and more.  

Nevertheless, there needs to be an alignment between therapist-claimed requirements and the actual patient requirements for meaningful technological developments. Fittings should also be designed so they can be donned quickly and fully removable in case patients face an emergency.  

Moreover, there are still questions on the effectiveness of exoskeletons as compared to treadmill-based or end-effector based locomotor training. Can exoskeletons provide better re-loading of the joints to allow muscle activation? How soon could patients after surviving a stroke, SCI or brain injury be exposed to exoskeleton gait training?  

Robotic technologies are not always used alone. A common question for exoskeleton technology would be if the use of virtual reality would enhance the effectiveness of the training.  

Figure 2: Yearly and Cumulative Number of Published Articles Related to Robotic Exoskeletons (adapted from Bao et al., 2019)[6]

Future of Exoskeletons 

In the next decade, we are expecting a boom in the exoskeleton industry with a CAGR of 20.5%[7]. According to the World Health Organisation, which kickstarted the Rehabilitation 2030: A Call For Action, the current growing global need for rehabilitation is currently unmatched by the existing rehabilitation services[8]. With the ageing population trend and the number of people living with chronic disabilities growing worldwide, we are hoping that exoskeletons will be developed with people in low- and middle-income areas in mind.  

We are also expecting more development in terms of hybrid exoskeletons – that combine FES or BCI, and more soft wearable exoskeletons or exosuits. With lighter and more affordable exoskeletons, we are hoping the adoption of exoskeleton technology would benefit the users to improving their quality of life. The future of rehabilitation robotics technology is looking bright.  

Note: The views reflected in this article and videos are the views of the author(s) and do not necessarily reflect the views of any company or organisation 


  1. Rupal et. al. (2016) Lower limb exoskeletons: a brief review. In Conference on mechanical engineering and technology (COMET-2016), IIT (BHU), Varanasi, Indiapp. 130-140 
  2. Bourgeois, S. p. (2018) 7-degree-of-freesom hybrid-manipulator exoskeleton for lower-limb motion capture. (Doctoral dissertation, Applied Sciences: School of Mechatronic Systems Engineering) 
  3. Gorgey, A.S., (2018) Robotic exoskeletons: The current pros and cons. World journal of orthopedics, 9(9), p.112 
  4. Wolff, J., Parker, C., Borisoff, J., Mortenson, W.B. and Mattie, J., (2014) A survey of stakeholder perspectives on exoskeleton technology. Journal of neuroengineering and rehabilitation, 11(1), p.169. 
  5. Miller, L. E., Zimmermann, A. K., and Herbert, W. G. (2016) Clinical effectiveness and safety of powered exoskeleton-assisted walking in patients with spinal cord injury: systematic review with meta-analysis. Medical Devices: Evidence and Research, 9, pp. 455-466 
  6. Bao, G., Pan, L., Fang, H., Wu, X., Yu, H., Cai, S., Yu, B., and Wan, Y. (2019) Academic review and perspectives on robotic exoskeletons. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 27(11), pp.2294-2304 
  7. Grand View Research, Inc. (2021) Available online: https://markets.businessinsider.com/news/stocks/exoskeleton-market-size-worth-953-1-million-by-2028-cagr-20-5-grand-view-research-inc-1030737245 [accessed 26th August 2021] 
  8. World Health Organisation (2017) Rehabilitation 2030: A Call For Action Available here: https://www.who.int/initiatives/rehabilitation-2030 [accessed: 26th August 2021] 


Executive Director, MotusAcademy
Incoming President, IISART
Co-Founder & Global CEO, Fourier Intelligence

Zen is a visionary and pioneering influencer in the field of MedTech and Robotics for Rehabilitation. He has been involved in several successful start-ups and businesses in Singapore, Switzerland, and China for over two decades, providing medical devices, healthcare solutions, and services for people with disabilities and neurological patients. He was nominated as one of the 40 under 40 most influential industry leaders in MedTech in 2012.

Zen holds multiple leadership roles, including the incoming president and ambassador of the International Industry Society for Advanced Rehabilitation Technology (IISART), General Chair for RehabWeek 2023, co-founder and Executive Director of the Swiss-based MotusAcademy Association, Managing Editor of the Journal of Rehabilitation Methods and Technologies (JRMT), and co-founder and Global CEO of Fourier Intelligence Group. Under his leadership, Fourier has raised over USD100 million, notably in 2022, from renowned investors such as Saudi Aramco Prosperity 7 venture and Softbank Vision Fund 2.

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