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Completed

NCT Number: NCT03134144

Chairless Chair Exoskeleton. Work-physiological-biomechanical Analysis of the Lower Extremities

Standing work is associated with increased risks of venous and musculoskeletal disorders; particularly low back pain is commonly reported in prolonged standing work. In manufacturing work, workstations often do not allow standing aids due to insufficient functional and spatial conditions. In 2014, the car manufacturer Audi introduced the lower leg exoskeleton developed by Noonee to their employees working in the factories. This exoskeleton, the 'Chairless Chair' has the advantage that standing work can be performed while technically sitting on this device. The exoskeleton offers the potential for reduced awkward body postures, but it is unclear which physiological and biomechanical loads are influenced and how. This proposal provides a study design evaluating the 'Chairless Chair' in a laboratory setting, by testing its effectiveness in terms of physiological and biomechanical parameters. It is suggested to compare different assembly tasks while wearing the exoskeleton, compared with not wearing the exoskeleton. The 'Chairless Chair' is developed in one size only, which is why we propose to include participants of different body height, which will enable us to investigate whether body height influences the effectiveness of wearing the device.

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Key information

Conditions

Healthy Musculoskeletal Diseases

Age range

18 year–40 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Institute for Occupational and Social Medicine and Health Services Research, University Hospital Tübingen, Faculty of Medicine, Eberhard Karls University Tübingen

Tübingen, Baden-Wurttemberg, 72074, Germany

About this study

Each participant was exposed to all experimental conditions, which were the following:

  • Standing without the exoskeleton
  • Sitting with the exoskeleton

For both experimental conditions, the working height was adjusted to the individual to become optimal. The working distance to the simulated assembly tasks was also adjusted to the individual to become optimal. Both the working height and distance were based on textual guidelines provided in DIN EN ISO 14738:2009-07.

Each work cycle consisted of assembling and disassembling the following three tasks:

  • Screwing
  • Clip fitting
  • Cable mounting

In addition, we investigated suboptimal working heights and distances. The results of these suboptimal conditions will not be reported in the results on this website, but in a separate publication.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age: between 18 and 40 years old;
  • Gender: male;
  • Voluntary informed consent (oral and written) is obligatory for study participation.

Exclusion criteria

  • Age: <18 and >40 years old;
  • Gender: female;
  • People under the influence of intoxicants, analgesics, or muscle relaxants;
  • Alcohol abuse;
  • People with cardiovascular diseases;
  • People with a heart pacemaker;
  • People with a disability who, due to their restriction at a workplace of this kind, will not be able to participate;
  • People with Diabetes Mellitus;
  • People with severe muscle contractions of the lower extremities, back or arms;
  • People with acute ailments or pain;
  • People who are unable to complete the examination program due to language or cognitive obstacles;
  • Depending on the degree of severity, people with diseases of the veins and joints of the lower extremities, spine, muscle disorders, symptomatic neurological-psychiatric diseases, acute pain syndromes, maladies or other current diseases.

Treatment and study plan

Exoskeleton "Chairless Chair"

Device

One solution to reduce the exposure of employees to associated risks for developing work-related musculoskeletal disorders is to use exoskeletons. Using such a device in dynamic environments has the advantage over, e.g., robotics because it does not need any programming or teaching of robots. Moreover, exoskeletons are worn at the body and do not have to overcome spatial issues. In a recent review, 26 different exoskeletons have been described of which only two were designed to support the lower body during heavy work (de Looze et al. 2015). For lower intensive work tasks, like assembly tasks in the automobile industry, no study has focused on using exoskeletons to relieve employees while performing the work standing.

Primary outcomes

  1. Center of Pressure

    Time frame: 10 minutes of 2 hours

    Indicator for the balance of the study participants. This outcome was measured using a force plate, in which the anteroposterior and mediolateral directions of the center of pressure are recorded. The center of pressure is a visual projection of the center of mass of the participant. For the anteroposterior direction of the center of pressure, a positive value [mm] represents the anterior direction and a negative value [mm] represents the posterior direction. For the mediolateral direction of the center of pressure, a positive value [mm] represents the right-lateral direction and a negative value [mm] represents the left-lateral direction.

    For this outcome, we recorded the anteroposterior direction of the center of pressure.

    The outcome is in mm, where neg. reflects the posterior direction and pos. the anterior direction.

  2. Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis)

    Time frame: 10 minutes of 2 hours

    Indicator for the muscular load in the lower back (M. erector spinae lumbalis) that may change when wearing the passive exoskeleton.

    The muscle activity was recorded using bipolar surface electromyography, during which two electrodes are placed on the muscle belly. The absolute value of muscle activity recordings is in microvolt, but since this is difficult to interpret, we have normalized this to a reference voluntary contraction that was executed by each participant prior to the experiment. The unit of measure for normalized muscle activity therefore is a percentage, i.e. a percentage of the electrical activity during the reference voluntary contraction [%RVE].

Secondary outcomes

  1. Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth)

    Time frame: 10 minutes of 2 hours

    The posture of the back may indicate whether the relative body posture changed when wearing the passive exoskeleton compared to not wearing the passive exoskeleton.

    In the current study, back posture was recorded using two gravimetric position sensors placed on the thoracic vertebrae T3 and lumbal vertebrae L3.

    The difference between both position sensors represented the trunk forward flexion angle [°].

  2. Subjective Feeling of Overall Discomfort

    Time frame: 10 minutes of 2 hours

    Indicate whether participants develop feelings of discomfort in different experimental conditions when wearing or not wearing the passive exoskeleton.

    Discomfort was recorded using an 11-point numeric rating scale, running from 0 (no discomfort at all) to 10 (maximally imaginable discomfort).

    So, the outocme is in [units on a scale from 0 to 10].

  3. Participant Evaluation

    Time frame: 2 hours

    A questionnaire indicating whether wearing the passive exoskeleton during simluated assembly tasks is evaluated as comfortable, feasible, and usable.

    Below, the 10 statements questions as part of the participant evaluation questionnaire are shown with an interpretation of the score.

    1 generally reflects "I do not agree at all" whereas 10 generally reflects "I fully agree".

    Depending on the question, a score closer or equal to 1 is better and 10 worse, or vice versa.

    Statements 1-8: a higher score (i.e., close to 10) is considered better Statements 9-10: a lower score (i.e., close to 1) is considered better

Sponsors and collaborators

Lead sponsor

University Hospital Tuebingen

Other

Registry information

Important dates

Study start
2017
Primary completion
2017
Study completion
2017
First posted
Apr 28, 2017
Registry last updated
Jun 16, 2020

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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