Healthy
Conditions
Keywords
Exoskeleton, Manual materials handling, Musculoskeletal disorders, Posture, Standing work, Muscle activity
Brief summary
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.
Detailed description
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.
Interventions
DEVICEExoskeleton 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.
Sponsors
University Hospital Tuebingen
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
MALE
Age
18 Years to 40 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Center of Pressure | 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. |
| Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis) | 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
| Measure | Time frame | Description |
|---|---|---|
| Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth) | 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 \[°\]. |
| Subjective Feeling of Overall Discomfort | 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 \[units on a scale from 0 to 10\]. |
| Participant Evaluation | 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 |
Countries
Germany
Participant flow
Recruitment details
Volunteering participants were recruited via the investigators that collaborated in this study.
Pre-assignment details
None of the recruited volunteering participants was excluded based on the exclusion criteria. One subject dropped out prior to the measurement due to time constraints.
Participants by arm
| Arm | Count |
|---|---|
| First Without Exoskeleton Then With Exoskeleton Subject will perform the conditions as described under model description first without and then with the exoskeleton. | 15 |
| First With Exoskeleton Then Without Subject will perform the conditions as described under model description first with and then without the exoskeleton. | 30 |
| Total | 45 |
Baseline characteristics
| Characteristic | First Without Exoskeleton Then With Exoskeleton | First With Exoskeleton Then Without | Total |
|---|---|---|---|
| Age, Continuous | 23.9 years STANDARD_DEVIATION 2.7 | 25.2 years STANDARD_DEVIATION 3 | 24.8 years STANDARD_DEVIATION 2.9 |
| Race and Ethnicity Not Collected | — | — | 0 Participants |
| Sex: Female, Male Female | 0 Participants | 0 Participants | 0 Participants |
| Sex: Female, Male Male | 15 Participants | 30 Participants | 45 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 45 | 0 / 45 |
| other Total, other adverse events | 0 / 45 | 0 / 45 |
| serious Total, serious adverse events | 0 / 45 | 0 / 45 |
Outcome results
Primary
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
Population: In total, two participants dropped out due to missing information with regard to the base of support, which is necessary to calculate the centre of pressure.
| Arm | Measure | Group | Value (MEDIAN) |
|---|---|---|---|
| First Without Exoskeleton Then With Exoskeleton | Center of Pressure | Experimental conditions without exoskeleton | -42.76 mm |
| First Without Exoskeleton Then With Exoskeleton | Center of Pressure | Experimental conditions with exoskeleton | -118.34 mm |
| First With Exoskeleton and Then Without Exoskeleton | Center of Pressure | Experimental conditions without exoskeleton | -34.98 mm |
| First With Exoskeleton and Then Without Exoskeleton | Center of Pressure | Experimental conditions with exoskeleton | -122.16 mm |
Primary
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
Population: Data of 7 participants are missing due to failed data recordings.
| Arm | Measure | Group | Value (MEDIAN) |
|---|---|---|---|
| First Without Exoskeleton Then With Exoskeleton | Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis) | Experimental conditions without the exoskeleton | 11.02 %RVE |
| First Without Exoskeleton Then With Exoskeleton | Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis) | Experimental conditions with the exoskeleton | 6.80 %RVE |
| First With Exoskeleton and Then Without Exoskeleton | Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis) | Experimental conditions without the exoskeleton | 7.78 %RVE |
| First With Exoskeleton and Then Without Exoskeleton | Muscle Activity of the Lower Back (M. Erector Spinae Lumbalis) | Experimental conditions with the exoskeleton | 8.29 %RVE |
Secondary
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
Population: Data of 8 subjects is missing due to failed recordings.
| Arm | Measure | Group | Value (MEDIAN) |
|---|---|---|---|
| First Without Exoskeleton Then With Exoskeleton | Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth) | Experimental conditions without the exoskeleton | 11.55 ° |
| First Without Exoskeleton Then With Exoskeleton | Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth) | Experimental conditions with the exoskeleton | 25.00 ° |
| First With Exoskeleton and Then Without Exoskeleton | Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth) | Experimental conditions without the exoskeleton | 5.10 ° |
| First With Exoskeleton and Then Without Exoskeleton | Back Posture: Upper Back Forward Flexion Angle With Respect to the Perpendicular (Earth) | Experimental conditions with the exoskeleton | 20.95 ° |
Secondary
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
Population: All participants could be included in the analysis.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | The exoskeleton is suitable for the simulated task | 8.3 units on a scale | Standard Deviation 1.8 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | The working posture was comfortable in low sit | 6.9 units on a scale | Standard Deviation 2.2 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I was able to work precisely with the exoskeleton | 9.1 units on a scale | Standard Deviation 1.1 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I felt safe to use the exoskeleton in high sit | 7.5 units on a scale | Standard Deviation 2.1 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I can imagine working with the exoskeleton longer | 7.4 units on a scale | Standard Deviation 2.2 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I felt safe to use the exoskeleton in low sit | 8.1 units on a scale | Standard Deviation 1.9 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | The exoskeleton was easy to operate / handle | 8.4 units on a scale | Standard Deviation 1.4 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I wanted to change position in high sit | 6.3 units on a scale | Standard Deviation 2.5 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | The working posture was comfortable in high sit | 5.9 units on a scale | Standard Deviation 2 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | I wanted to change position in low sit | 4.9 units on a scale | Standard Deviation 2.6 |
| First Without Exoskeleton Then With Exoskeleton | Participant Evaluation | The exoskeleton was comfortable | 6.4 units on a scale | Standard Deviation 2.1 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I wanted to change position in low sit | 5.0 units on a scale | Standard Deviation 2.8 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | The exoskeleton was comfortable | 6.9 units on a scale | Standard Deviation 1.9 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | The exoskeleton was easy to operate / handle | 8.7 units on a scale | Standard Deviation 1.3 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I was able to work precisely with the exoskeleton | 8.7 units on a scale | Standard Deviation 1.3 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | The exoskeleton is suitable for the simulated task | 8.1 units on a scale | Standard Deviation 1.6 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I can imagine working with the exoskeleton longer | 6.9 units on a scale | Standard Deviation 2.1 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | The working posture was comfortable in high sit | 5.1 units on a scale | Standard Deviation 2 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | The working posture was comfortable in low sit | 7.2 units on a scale | Standard Deviation 1.7 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I felt safe to use the exoskeleton in high sit | 6.6 units on a scale | Standard Deviation 2.1 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I felt safe to use the exoskeleton in low sit | 7.8 units on a scale | Standard Deviation 1.4 |
| First With Exoskeleton and Then Without Exoskeleton | Participant Evaluation | I wanted to change position in high sit | 5.6 units on a scale | Standard Deviation 2.9 |
Secondary
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
Population: All participants were included in this analysis.
| Arm | Measure | Group | Value (MEDIAN) |
|---|---|---|---|
| First Without Exoskeleton Then With Exoskeleton | Subjective Feeling of Overall Discomfort | Experimental conditions without the exoskeleton | 0 units on a scale |
| First Without Exoskeleton Then With Exoskeleton | Subjective Feeling of Overall Discomfort | Experimental conditions with the exoskeleton | 2 units on a scale |
| First With Exoskeleton and Then Without Exoskeleton | Subjective Feeling of Overall Discomfort | Experimental conditions without the exoskeleton | 0 units on a scale |
| First With Exoskeleton and Then Without Exoskeleton | Subjective Feeling of Overall Discomfort | Experimental conditions with the exoskeleton | 0 units on a scale |