An interventional study of Exoskeleton "Chairless Chair" in Healthy, sponsored by University Hospital Tuebingen. Completed at 1 site in Germany. Open to male participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2020-06-16.
Sponsored by University Hospital Tuebingen · Not applicable, Interventional, and Basic science
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.
Each participant was exposed to all experimental conditions, which were the following:
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:
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.
University Hospital Tuebingen is the lead sponsor of 476 studies on the registry; 104 are open to participants now.
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Exclusion Criteria:
Subject will perform the conditions as described under "model description" first without the exoskeleton and then with the exoskeleton.
Device: Exoskeleton "Chairless Chair"
Subject will perform the conditions as described under "model description" first with the exoskeleton and then without the exoskeleton.
Device: Exoskeleton "Chairless Chair"
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.
Center of Pressure
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.
Time frame: 10 minutes of 2 hours
Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis)
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 \[%RVE\].
Time frame: 10 minutes of 2 hours
Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth)
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 \[°\].
Time frame: 10 minutes of 2 hours
Subjective Feeling of Overall Discomfort
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 \[units on a scale from 0 to 10\].
Time frame: 10 minutes of 2 hours
Participant Evaluation
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
Time frame: 2 hours
Volunteering participants were recruited via the investigators that collaborated in this study.
| Milestone | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton and Then Without Exoskeleton |
|---|---|---|
| Started | 15 | 30 |
| Completed | 15 | 30 |
| Not completed | 0 | 0 |
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.
| mm | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton and Then Without Exoskeleton |
|---|---|---|
| Experimental conditions without exoskeleton | -42.76 (-48.19 to -25.55) | -34.98 (-49.16 to -22.18) |
| Experimental conditions with exoskeleton | -118.34 (-128.42 to -107.43) | -122.16 (-130.80 to -111.58) |
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 \[%RVE\].
| %RVE | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton and Then Without the Exoskeleton |
|---|---|---|
| Experimental conditions without the exoskeleton | 11.02 (7.06 to 13.89) | 7.78 (6.62 to 11.70) |
| Experimental conditions with the exoskeleton | 6.80 (5.39 to 11.11) | 8.29 (4.58 to 11.44) |
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 \[°\].
| ° | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without Exoskeleton |
|---|---|---|
| Experimental conditions without the exoskeleton | 11.55 (4.83 to 17.10) | 5.10 (-3.31 to 10.83) |
| Experimental conditions with the exoskeleton | 25.00 (14.89 to 36.85) | 20.95 (12.30 to 31.08) |
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 \[units on a scale from 0 to 10\].
| units on a scale | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without Exoskeleton |
|---|---|---|
| Experimental conditions without the exoskeleton | 0 (0 to 0) | 0 (0 to 1.25) |
| Experimental conditions with the exoskeleton | 2 (0 to 2) | 0 (0 to 2) |
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
| units on a scale | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without |
|---|---|---|
| The exoskeleton was comfortable | 6.4 ± 2.1 | 6.9 ± 1.9 |
| The exoskeleton was easy to operate / handle | 8.4 ± 1.4 | 8.7 ± 1.3 |
| I was able to work precisely with the exoskeleton | 9.1 ± 1.1 | 8.7 ± 1.3 |
| The exoskeleton is suitable for the simulated task | 8.3 ± 1.8 | 8.1 ± 1.6 |
| I can imagine working with the exoskeleton longer | 7.4 ± 2.2 | 6.9 ± 2.1 |
| The working posture was comfortable in high sit | 5.9 ± 2.0 | 5.1 ± 2.0 |
| The working posture was comfortable in low sit | 6.9 ± 2.2 | 7.2 ± 1.7 |
| I felt safe to use the exoskeleton in high sit | 7.5 ± 2.1 | 6.6 ± 2.1 |
| I felt safe to use the exoskeleton in low sit | 8.1 ± 1.9 | 7.8 ± 1.4 |
| I wanted to change position in high sit | 6.3 ± 2.5 | 5.6 ± 2.9 |
| I wanted to change position in low sit | 4.9 ± 2.6 | 5.0 ± 2.8 |
Collected over Through study completion, i.e. 1 day. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Without Exoskeleton | 0/45 (0%) | 0/45 (0%) | 0/45 (0%) |
| With Exoskeleton | 0/45 (0%) | 0/45 (0%) | 0/45 (0%) |
Three additional subjects were recruited on top of the the sample size calculation, because three of the earlier measured subject had some missing data due to technical problems.
| Age, Continuous(years) | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without | Total |
|---|---|---|---|
| Mean | 23.9 ± 2.7 | 25.2 ± 3.0 | 24.8 ± 2.9 |
| Sex: Female, Male(Participants) | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without | Total |
|---|---|---|---|
| Female | 0 | 0 | 0 |
| Male | 15 | 30 | 45 |
| Race and Ethnicity Not Collected(Participants) | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without | Total |
|---|---|---|---|
| Count of participants | — | — | 0 |
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University Hospital Tuebingen