Trial Outcomes & Findings for Work Physiological-Biomechanical Analysis of a Passive Exoskeleton to Support Occupational Lifting and Flexing Processes (NCT NCT03725982)

NCT ID: NCT03725982

Last Updated: 2023-07-12

Results Overview

Root-mean-square (RMS) of the electrical activity of the erector spinae muscle using surface electromyography (sEMG). The sEMG signals will be continuously recorded, and the RMS will be normalized to a maximal voluntary contraction (%MVE) and averaged over the time period of each experimental condition.

• Recruitment status: COMPLETED
• Study phase: NA
• Target enrollment: 39 participants
• Primary outcome timeframe: Average RMS-value (%MVE) over the time period running from baseline (0 min) to directly after (1.5 min) the experimental condition
• Results posted on: 2023-07-12

Participant Flow

Volunteering participants were recruited via the collaborating investigators and by means of announcement e-mails to employees and students of the University and Hospital of Tübingen.

39 volunteering participants were recruited, of which 2 were excluded from the study prior to the measurement due to a too high BMI (> 30 kg/m2). A 3rd participant was excluded because he was the first that was measured and we had to adjust a few things to the measurement afterwards.

Participant milestones

Measure	First With Exoskeleton Then Without Exoskeleton Subject will perform the conditions (simulated, simplified, industrial standing work) as described under "model description" first with and then without the exoskeleton.	First Without Exoskeleton Then With Exoskelton Subject will perform the conditions (simulated, simplified, industrial standing work) as described under "model description" first without and then with the exoskeleton.
First Intervention STARTED	20	19
First Intervention COMPLETED	19	17
First Intervention NOT COMPLETED	1	2
Second Intervention STARTED	19	17
Second Intervention COMPLETED	19	17
Second Intervention NOT COMPLETED	0	0

Reasons for withdrawal

Measure	First With Exoskeleton Then Without Exoskeleton Subject will perform the conditions (simulated, simplified, industrial standing work) as described under "model description" first with and then without the exoskeleton.	First Without Exoskeleton Then With Exoskelton Subject will perform the conditions (simulated, simplified, industrial standing work) as described under "model description" first without and then with the exoskeleton.
First Intervention Withdrawal by Subject	0	1
First Intervention Physician Decision	1	1

Baseline Characteristics

Work Physiological-Biomechanical Analysis of a Passive Exoskeleton to Support Occupational Lifting and Flexing Processes

Baseline characteristics by cohort

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subject first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subject first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.	Total n=36 Participants Total of all reporting groups
Age, Continuous	23.9 years STANDARD_DEVIATION 3.8 • n=5 Participants	28.1 years STANDARD_DEVIATION 4.6 • n=7 Participants	25.9 years STANDARD_DEVIATION 4.6 • n=5 Participants
Sex: Female, Male Female	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Sex: Female, Male Male	19 Participants n=5 Participants	17 Participants n=7 Participants	36 Participants n=5 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) Asian	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) Black or African American	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) White	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) Unknown or Not Reported	19 Participants n=5 Participants	17 Participants n=7 Participants	36 Participants n=5 Participants
Region of Enrollment Germany	19 Participants n=5 Participants	17 Participants n=7 Participants	36 Participants n=5 Participants
Weight	73.3 kg STANDARD_DEVIATION 9.4 • n=5 Participants	73.8 kg STANDARD_DEVIATION 8.5 • n=7 Participants	73.5 kg STANDARD_DEVIATION 8.9 • n=5 Participants
Height	179.7 cm STANDARD_DEVIATION 6.3 • n=5 Participants	178.0 cm STANDARD_DEVIATION 6.7 • n=7 Participants	178.9 cm STANDARD_DEVIATION 6.4 • n=5 Participants
Body mass index (BMI)	22.6 kg/m^2 STANDARD_DEVIATION 2.1 • n=5 Participants	23.3 kg/m^2 STANDARD_DEVIATION 2.1 • n=7 Participants	22.9 kg/m^2 STANDARD_DEVIATION 2.1 • n=5 Participants

PRIMARY outcome

Timeframe: Average RMS-value (%MVE) over the time period running from baseline (0 min) to directly after (1.5 min) the experimental condition

Population: The results of the effect of wearing the exoskeleton during the static task are reported below, without taking into account the working direction (frontal or lateral, i.e. without or with trunk rotation, respectively). Note: the overall number of participants analyzed deviates in the first arm because data of one subject was excluded.

Root-mean-square (RMS) of the electrical activity of the erector spinae muscle using surface electromyography (sEMG). The sEMG signals will be continuously recorded, and the RMS will be normalized to a maximal voluntary contraction (%MVE) and averaged over the time period of each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=18 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Muscular Activity of Erector Spinae Muscle. RMS-value during first intervention period	11.2 %MVE Interval 8.6 to 16.0	11.1 %MVE Interval 8.6 to 14.8
Muscular Activity of Erector Spinae Muscle. RMS-value during second intervention period	12.3 %MVE Interval 9.0 to 17.6	10.4 %MVE Interval 7.5 to 13.1

PRIMARY outcome

Timeframe: Average RMS-value (%RVE) over the time period running from baseline (0 min) to directly after (1.5 min) the experimental condition

Population: The results of the effect of wearing the exoskeleton during the static task are reported below, without taking into account the working direction (frontal or lateral, i.e. without or with trunk rotation, respectively).

Root-mean-square (RMS) of the electrical activity of the biceps femoris muscle using surface electromyography (sEMG). The sEMG signals will be continuously recorded, and the RMS will be normalized to a reference voluntary contraction (%RVE) and averaged over the time period of each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Muscular Activity of Biceps Femoris Muscle. RMS during first intervention period	26.6 %RVE Interval 16.3 to 39.3	38.7 %RVE Interval 23.9 to 57.5
Muscular Activity of Biceps Femoris Muscle. RMS during second intervention period	35.8 %RVE Interval 24.4 to 45.8	31.3 %RVE Interval 20.2 to 55.7

PRIMARY outcome

Timeframe: Average thoracic kyphosis over time period baseline (0 min) to directly after (1.5 min) the experimental condition

The posture of the upper spine (thoracic kyphosis) determined using 2D gravimetric position sensors placed on the thoracic vertebrae T1 and lumbar vertebrae L1. The difference value between both sensors reflects the thoracic kyphosis, which was averaged over each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Posture (Thoracic Kyphosis) Average angle during first intervention period	12.0 degrees Interval 7.5 to 15.8	15.4 degrees Interval 8.0 to 21.0
Posture (Thoracic Kyphosis) Average angle during second intervention period	14.5 degrees Interval 7.6 to 19.5	13.9 degrees Interval 8.8 to 21.3

PRIMARY outcome

Timeframe: Average lumbar lordosis over time period baseline (0 min) to directly after (1.5 min) the experimental condition

The posture of the lower spine (lumbar lordosis) determined using 2D gravimetric position sensors placed on the lumbar vertebrae L1 and L5. The difference value between both sensors reflects the lumbar lordosis, which was averaged over each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Posture (Lumbar Lordosis) Average angle during first intervention period	11.8 degrees Interval 10.0 to 14.2	13.2 degrees Interval 9.4 to 17.7
Posture (Lumbar Lordosis) Average angle during second intervention period	12.2 degrees Interval 10.1 to 14.0	13.3 degrees Interval 10.4 to 16.1

PRIMARY outcome

Timeframe: Average trunk flexion over time period baseline (0 min) to directly after (1.5 min) the experimental condition

The posture of the trunk determined using a 2D gravimetric position sensor placed on the thoracic vertebrae T10. The flexion angle of the sensor was averaged over each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Posture (Trunk Flexion) Average angle during first intervention period	38.5 degrees Interval 36.5 to 41.1	39.6 degrees Interval 35.6 to 42.2
Posture (Trunk Flexion) Average angle during second intervention period	37.9 degrees Interval 35.7 to 40.5	39.9 degrees Interval 35.9 to 43.5

PRIMARY outcome

Timeframe: Average hip flexion over time period baseline (0 min) to directly after (1.5 min) the experimental condition

The posture of the hip (hip flexion) determined using 2D gravimetric position sensors placed on the lumbar vertebrae L5 and the upper leg (femur). The difference value between both sensors reflects the hip flexion, which was averaged over each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Posture (Hip Flexion) Average angle during first intervention period	39.9 degrees Interval 33.8 to 45.8	33.1 degrees Interval 24.7 to 38.4
Posture (Hip Flexion) Average angle during second intervention period	29.8 degrees Interval 23.6 to 38.3	40.4 degrees Interval 32.1 to 47.1

PRIMARY outcome

Timeframe: Average knee flexion over time period baseline (0 min) to directly after (1.5 min) the experimental condition

The posture of the knee (knee flexion) determined using 2D gravimetric position sensors placed on the upper leg (femur) and lower leg (tibia). The difference value between both sensors reflects the knee flexion, which was averaged over each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Posture (Knee Flexion) Average angle during first intervention period	16.4 degrees Interval 9.4 to 26.4	11.7 degrees Interval 3.7 to 17.5
Posture (Knee Flexion) Average angle during second intervention period	9.0 degrees Interval 2.9 to 16.7	17.9 degrees Interval 10.5 to 25.6

PRIMARY outcome

Timeframe: Average knee compression force (KCF) over the time period running from baseline (0 min) to directly after (1.5 min) the experimental condition

Population: For some of the participants, we could not analyze the knee compression force (KCF) data, because some information was missing to apply the modelling procedure.

The knee compression force (KCF) is calculated using 2D inverse modelling with continuous recordings from 2D gravimetric position sensors (for joint angles) and a force plate (for ground reaction forces). The average knee compression force will be calculated over each experimental condition and summarized for both the left and right knee, since the task is executed in the frontal plane.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=15 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=14 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Knee Compression Force Average KCF during first intervention period	845 N Interval 741.0 to 897.0	742 N Interval 609.0 to 892.0
Knee Compression Force Average KCF during second intervention period	807 N Interval 747.0 to 868.0	874 N Interval 660.0 to 963.0

SECONDARY outcome

Timeframe: Average RMS-value (%RVE) over the time period running from baseline (0 min) to directly after (1.5 min) the experimental condition.

Root-mean-square (RMS) of the electrical activity of the rectus abdominis, vastus lateralis, gastrocnemius medialis and trapezius descendens muscles using surface electromyography (sEMG). The sEMG signals will be continuously recorded, and the RMS will be normalized to a refeernce voluntary contraction (%RVE) and averaged over the time period of each experimental condition.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Muscular Activity of Rectus Abdominis, Vastus Lateralis, Gastrocnemius Medialis and Trapezius Descendens Muscles. Rectus Abdominis	1.85 %RVE Interval 0.98 to 2.72	1.57 %RVE Interval 0.88 to 2.26
Muscular Activity of Rectus Abdominis, Vastus Lateralis, Gastrocnemius Medialis and Trapezius Descendens Muscles. Vastus Lateralis	3.85 %RVE Interval 2.06 to 5.64	3.35 %RVE Interval 1.99 to 4.71
Muscular Activity of Rectus Abdominis, Vastus Lateralis, Gastrocnemius Medialis and Trapezius Descendens Muscles. Gastrocnemius Medialis	54.11 %RVE Interval 30.63 to 77.59	54.11 %RVE Interval 34.75 to 73.58
Muscular Activity of Rectus Abdominis, Vastus Lateralis, Gastrocnemius Medialis and Trapezius Descendens Muscles. Trapezius Descendens	3.77 %RVE Interval 0.71 to 6.83	4.90 %RVE Interval 1.21 to 8.6

SECONDARY outcome

Timeframe: Change from baseline (0 min) to directly after (1.5 min) both experimental conditions

Discomfort (RPD) was assessed using an 11-point numeric rating scale (NRS), ranging from 0 (no discomfort at all) to 10 (maximally imaginable discomfort). It was assessed directly before (0 min) and directly after (1.5 min) each experimental condition. The experimental conditions consisted of either static or dynamic tasks, that lasted up to 1.5 minutes.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=19 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=17 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Rating of Perceived Discomfort (RPD) RPD after first intervention period	0.3 units on a scale Standard Deviation 0.8	0.2 units on a scale Standard Deviation 0.6
Rating of Perceived Discomfort (RPD) RPD after second intervention period	0.5 units on a scale Standard Deviation 1.0	0.2 units on a scale Standard Deviation 0.7

SECONDARY outcome

Timeframe: Average heart activity over time period baseline (0 min) to directly after (1.5 min) the experimental condition

Continuous recording electrocardiography allows calculating the heart rate, a parameter reflecting the central stress state of the participant. The average heart rate will be calculated per time period.

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Heart Rate	85.29 beats per minute Standard Deviation 10.19	83.16 beats per minute Standard Deviation 10.49

SECONDARY outcome

Timeframe: Directly after the experimental condition during which the exoskeleton was worn (~ 4.5-6.5 min)

The NASA Task Load Index (TLX) of Hart and Staveland (1988) will be used to evaluate workload. This standardized tool contains six dimensions (mental demand, physical demand, temporal demand, own performance, effort, frustration), of which each scale ranges from from 0 (low) to 100 (high).

We will include three dimensions of interest, i.e. physical demand, temporal demand, effort, and calculate the unweighted average of the score of these three dimensions (Hoonakker et al. 2011).

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Evaluation of Workload Physical Demand	2.31 units on a scale Standard Deviation 1.58	1.67 units on a scale Standard Deviation 1.10
Evaluation of Workload Temporal Demand	1.10 units on a scale Standard Deviation 1.35	0.88 units on a scale Standard Deviation 1.01
Evaluation of Workload Effort	2.10 units on a scale Standard Deviation 1.30	1.49 units on a scale Standard Deviation 1.00

SECONDARY outcome

Timeframe: Directly after the experiment (~2.5 hours)

Population: Reportedin units on a scale: SUS: 0 (low usability) to 100 (high usability) TUI-userfriendliness: 3 (totaly not applicable) to 21 (totally applicable) TUI-scepticism: 4 (totaly not applicable) to 28 (totaly applicable)

This questionnaire will consist of questions about usability and acceptance of the intervention (the Laevo device), stemming from standardized questions from existing questionnaires, including:

• the System Usability Scale (SUS): 10 statements about subjective perception of interaction with the Laevo system to be evaluated on a scale ranging from 1 (disagree) to 5 (agree);
• the Technology Usage Inventory (TUI): 30 statements on technology-specific and psychological factors with respect to the Laevo to be evaluated on a scale ranging from 1 (not true) to 7 (true); of these 30 questions, the investigators include only 7 statements belonging to the domains 'usability' and 'skepticism'.

The questionnaire can only be filled out after the condition within which the technology (here: exoskeleton) was used. That means that results are only provided and, thus, reported from the arm "with exoskeleton".

Outcome measures

Measure	With Exoskeleton, Then Without Exoskeleton n=36 Participants Subjects first performed the conditions (simulated, simplified, industrial standing work) with the exoskeleton, then without the exoskeleton.	Without Exoskeleton, Then With Exoskeleton Subjects first performed the conditions (simulated, simplified, industrial standing work) without the exoskeleton, then with the exoskeleton.
Self-developed Participant Evaluation Questionnaire System Usability Scale (SUS) - total score	75.44 units on a scale Standard Deviation 12.87	—
Self-developed Participant Evaluation Questionnaire Technology Usability Inventory (TUI) - user friendlines score	17.92 units on a scale Standard Deviation 2.61	—
Self-developed Participant Evaluation Questionnaire Technology Usability Inventory (TUI) - scepticims	11.53 units on a scale Standard Deviation 4.08	—

Adverse Events

With Exoskeleton

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Without Exoskeleton

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Tessy Luger

Institute of Occupational and Social Medicine and Health Services Research

Phone: 004970712984364

Email: Tessy.Luger@med.uni-tuebingen.de

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place