Work Physiological-Biomechanical Analysis of a Passive Exoskeleton to Support Occupational Lifting and Flexing Processes
Phase: NA
Conditions: Passive Upper-limb Exoskeleton
Sponsor: University Hospital Tuebingen

 
 
 
 
 
ADVANCE 
ARBEITSPHYSIOLOGISCH-BIOMECHANISCHE ANALYSE EINES PASSIVEN 
EXOSKELETTS ZUR UNTERSTÜTZUNG VON BERUFLICHEN HEBE- UND 
BEUGEVORGÄNGEN 
 
ADVANCE 
WORK PHYSIOLOGICAL-BIOMECHANICAL ANALYSIS OF A PASSIVE 
EXOSKELETON TO SUPPORT OCCUPATIONAL LIFTING AND FLEXING 
PROCESSES 
 
FOR REVIEW BY THE 
ETHICS COMMITTEE 
OF THE 
EBERHARD-KARLS-UNIVERSITY OF TÜBINGEN 
 
Date of protocol 
17.01.2019 
Version of protocol 
V3 
Head of study (UKT) 
Dr. Benjamin Steinhilber & Dr. Tessy Luger & 
Dipl.-Ing. Robert Seibt, Mona Bär M.Sc. 
Institute of Occupational and Social Medicine and Health 
Services Research 
Wilhelmstraße 27 
72074 Tübingen 
℡ 07071-29-86805 |  07071-29-4362 
Director 
Prof. Dr. Monika A. Rieger 
Other researchers 
Sylvia Weymann (Bachelor Medicine Technique) 
Gianluca Caputo (Bachelor Medicine Technique)

 
 
 
 
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I 
Abstract 
Introduction: Industrial tasks that are characterized by high loads, a high repetition rate, and / or  
awkward body postures, put employees at higher risk to develop work-related musculoskeletal 
disorders (WRMSD), especially low back pain. To counteract the prevalence of WRMSD, human-robot 
interaction could improve the power of a person and reduce the physical strain. For the lower back, a 
reduction of spinal loading could be helpful. The passive upper-extremity exoskeleton Laevo® is 
developed to support physically heavy work: it supports the back during bending and should, 
consequently, result in less low back pain (Laevo®, the Netherlands). 
Objectives: The primary aim of this study is to assess to what extent wearing the exoskeleton 
changes knee compression force, reduces muscular load on the back muscles, and changes the 
muscular load on other body parts such as the legs and shoulders in different tasks (static vs. 
dynamic) and different postures (trunk flexion vs. trunk flexion and rotation). The secondary aim of 
this study is to investigate the relation between trunk flexion angle, load carried and muscular stress 
of the back muscle. The tertiary aim of this study is to estimate internal loadings on the spine, using a 
lumbar spine model. The quaternary aim of this study is to assess the performance of subjects during 
functional activities (e.g., stair climbing) when wearing the exoskeleton. 
Methods: For the primary aim, we will test six different experimental conditions in the laboratory, 
which are a combination of exoskeleton (with vs. without Laevo®), task (static vs. dynamic), and knee 
angle only for the dynamic task (flexed vs. extended). Within each combination, we will test three 
different working directions (front vs. left vs. right), realized by changing the working posture (trunk 
flexion vs. left trunk rotation vs. right trunk rotation). Using the single Williams design for six 
conditions, we estimated our sample size to include 36 subjects (i.e., a multiple of six). Using a force 
plate, acceleration and postural sensors, we can estimate knee compression force using 2D inverse 
modelling. With an electromyographic system, we can record the muscle activity of selected target 
muscles at different body parts (i.e., legs, trunk, and shoulders). The heart rate will be recorded using 
electrocardiography. For the secondary aim, we will test four different conditions, which are a 
combination of exoskeleton (with vs. without Laevo®) and knee angle (flexed vs. extended). Within 
each combination, we will test three different loads carried (0kg, 8kg, 16kg) and five different trunk 
flexion angles (0°, 30°, 60°, 60°, 30°). We will record muscle activity, position, heart rate and ground 
reaction forces. For the tertiary aim, we will use the lumbar spine model developed by the research 
group Biomechanics and Biorobotics of the research cluster Simulation Technology of the University 
of Stuttgart. The model includes a detailed lumber spine with non-linear discs, ligaments, and 
muscles. Using the measurements of the experiment, this model is able to predict how internal 
forces in the lumbar spine change as a result of external forces (i.e., wearing and using the Laevo® 
exoskeleton). For the quaternary aim, we will test three different functional tests. The main outcome 
for the quaternary aim is performance, which could be either time recorded or difficulty rated on a 
standardized 11-point numeric rating scale. 
Analyses: For the primary aim, the effects of exoskeleton (with vs. without), task (static vs. dynamic), 
knee angle (flexed vs. extended; only for the dynamic task), and working posture (trunk flexion vs. 
left trunk rotation vs. right trunk rotation) will be assessed using a four-factor repeated-measures 
analysis of variance (RM-ANOVA) or a generalized estimating equation (GEE) which is more robust. 

 
 
 
 
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For the secondary aim, the effects of exoskeleton (with vs. without), knee angle (flexed vs. 
extended), load carrier (0kg vs. 8kg vs. 16kg), and trunk flexion angle (0° vs. 30° vs. 60°) will be 
assessed using a RM-ANOVA or GEE. For the quaternary aim, the effect of exoskeleton (with vs. 
without) on performance of each functional test will be assessed using a paired T-Test. 
Data protection: All participating subjects will receive a refund of € 45 after study completion. 
Subjects will sign an informed consent and their data will be numerically pseudonymized to 
guarantee anonymity. 
II 
Keywords 
Passive exoskeleton; forward trunk flexion; trunk rotation; inverse dynamics; muscle activity; 
modelling 
 
 

 
 
 
 
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III 
Attachments 
Attachment 1: Experimentelle Bedingungen, randomisiert 
Attachment 2: Anwerbetext zur Studie 
Attachment 3: Probandeninformation 
Attachment 4A: Einwilligungserklärung 
Attachment 4B: Datenschutzerklärung 
Attachment 5: Ein- und Ausschlusskriterien 
Attachment 6: Allgemeine Angaben 
Attachment 7: Nordische Fragebogen 
Attachment 8: Selbsteinschätzung von Beschwerden 
Attachment 9: Beschwerden Intensität & Körperregion 
Attachment 10: NASA-TLX 
Attachment 11: Bewertungsfragebogen 
Attachment 12: EU-Konformitätserklärung – Laevo® Exoskelett | Laevo B.V. 
Attachment 13: EU-Konformitätserklärung – PS11 Messgeräte | Thumedi GmbH & Co. KG 
Attachment 14: EU-Konformitätserklärung – PS12 Messgeräte | Thumedi GmbH & Co. KG 
Attachment 15: EU-Konformitätserklärung – Force Plate | Bertec GmbH 
Attachment 16: EU-Konformitätserklärung – Force Sensor | ME Meßsysteme GmbH 
 
 
 
 

 
 
 
 
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Table of content 
I 
ABSTRACT 
I 
II 
KEYWORDS 
II 
III ATTACHMENTS 
III 
1 
ABBREVIATIONS 
1 
2 
BACKGROUND 
2 
3 
OBJECTIVES 
4 
4 
STUDY DESIGN AND STUDY POPULATION 
5 
4.1 
STUDY DESIGN 
5 
4.1.1 
Independent variables 
5 
4.1.2 
Outcomes 
5 
4.2 
STUDY POPULATION 
5 
4.3 
IN- AND EXCLUSION CRITERIA 
6 
4.3.1 
Inclusion criteria 
6 
4.3.2 
Exclusion criteria 
6 
4.4 
RECRUITMENT 
7 
5 
TIMETABLE 
8 
5.1 
WP 1: STATIC WORK TASKS 
8 
5.2 
WP 2: DYNAMIC WORK TASKS 
9 
5.3 
WP 3: LUMBAR SPINE MODEL 
9 
6 
STUDY PROCEDURE 
10 
6.1 
EXPERIMENTAL TASKS 
10 
6.2 
MODELLING OF THE LUMBAR SPINE 
11 
6.3 
STATIC TRUNK FORWARD FLEXION ANGLE WHILE HOLDING A LOAD 
12 
6.4 
FUNCTIONAL TASKS 
13 

 
 
 
 
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6.5 
EXPERIMENTAL PROCEDURE 
13 
6.6 
OUTPUT 
14 
7 
MEASUREMENT METHODS AND ANALYSES 
15 
7.1 
GENERAL DATA 
15 
7.2 
MUSCLE ACTIVITY 
15 
7.3 
KINEMATICS: POSTURE AND FORCE 
15 
7.4 
REFERENCE MEASUREMENTS 
17 
7.5 
HEART RATE 
17 
7.6 
DISCOMFORT 
17 
7.7 
FUNCTIONAL TESTS 
18 
7.8 
RELATION STATIC TRUNK FORWARD FLEXION ANGLE, CARRIED LOAD AND MUSCULAR STRESS / 
SPINAL LOAD 
18 
7.9 
PARTICIPANT EVALUATION 
18 
7.11 
STATISTICAL ANALYSIS 
19 
8 
RISK FOR THE PARTICIPANT 
20 
9 
DATA PROTECTION 
21 
10 STUDY FINANCE 
22 
11 PERSONNEL STAFF 
23 
11.1 
WORK PACKAGES 1 & 2 
23 
11.2 
WORK PACKAGE 3 
23 
11 REFERENCES 
24 

 
 
 
 
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1 
Abbreviations 
%RVE  
percentage of the reference voluntary electrical activity 
2D 
 
two-dimensional 
3D 
 
three-dimensional 
ANOVA  
analysis of variance 
EMG 
 
electromyography 
⃗ 
 
force 
⃗ 
 
gravitational force 
IED 
 
inter-electrode distance 
L5 
 
fifth lumbar vertebra 
LCT 
 
Lift and Carry Test 
M 
 
moment 
MPF 
 
median power frequency 
 
 
angle 
RPD 
 
rating of perceived discomfort 
RMS 
 
root-mean-square 
RVC 
 
reference voluntary contraction 
RVE 
 
reference voluntary electrical activity 
SCT 
 
Stair Climbing Test 
SimTech 
Simulation Technology 
SLS 
 
Single-Leg Stance 
SUS 
 
System Usability Scale 
T3 
 
third thoracic vertebra 
TAM2  
Technology Acceptance Model 2 
UKT 
 
University Hospital Tübingen 
WP 
 
work package 
WRMSD 
work-related musculoskeletal disorders  
 
 
 

 
 
 
 
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2 
Background 
Due to the exposure to physically demanding work, repetitive movements and awkward body 
postures in industry (van Rijn et al., 2010), a considerable amount of employees develops work-
related musculoskeletal disorders (WRMSD; Wang et al., 2017). Low back pain is one of the most 
prevalent disorders in the general population (Scott et al., 2010), but is also apparent as WRMSD 
(Irwin et al., 2007). Because industry cannot be completely automated, human-robot cooperation is a 
solution to provide assistance or support for human motions or actions, but does not influence the 
flexibility or creativity of motions and actions (MacDougall, 2014). 
One type of human-robot cooperation is the exoskeleton, which is a wearable, external system 
improving the power of a person (de Looze et al., 2015). Exoskeletons can be distinguished by their 
technical functions, i.e. as an active or a passive system and by its target body part it supports. 
Exoskeletons are mainly used for rehabilitation or other medical purposes supporting daily activities 
like walking, standing up, or grasping (Viteckova et al., 2013). However, exoskeletons in occupational 
settings are not often used, mainly because there are no specific guidelines available for safety or 
technical issues. This means that exoskeletons will not yet be implemented on a large scale in 
industry to assist work-related activities. Aspects such as perceived discomfort, body alignment and 
weight of the exoskeleton are important aspects that need to be considered when optimizing 
exoskeletons for implementation in occupational settings. However, several reviews have been 
conducted already, including a review on the two key applications of exoskeleton systems (Yang et 
al., 2008), on the characteristics of exoskeleton robot systems for power assistance (Lee et al., 2012), 
on the compatibility of lower limb exoskeletons with the user (Viteckova et al., 2013), and on the 
effectiveness of wearing exoskeletons on the physical loading of the body (de Looze et al., 2015). 
The review of Yang et al. (2008) gives a great overview of the main two fields of application of 
exoskeletons, which are teleoperation and power amplification. Lee et al. (2012) in their review 
report on the different classifications of exoskeletons, including (1) power assistant or power 
augmented systems, (2) anthropomorphic, quasi-anthropomorphic, or non-anthropomorphic, (3) 
active, passive, or quasi-passive, and (4) the level of human-robot interactions. Both reviews point 
out that a lot still needs to be achieved with regard to the level of the exoskeleton’s 
anthropomorphicity, as it appears to be very difficult to mechanically pursue natural human motion. 
Viteckova et al. (2013) add to this challenge the problem of the high energy consumption of active 
exoskeletons and the composition of the exoskeletons which, with a high weight, require high 
metabolic consumption of the wearer. The review of de Looze et al. (2015) was the only one 
specifically evaluating the effect of wearing exoskeletons on the physical loading of the wearer’s 
body. They found that muscular activity was reduced by 10-40% when wearing passive systems and 
up to 80% when wearing active systems. However, they also point out that several challenges need 
to be overcome, including degeneration of the exoskeleton’s target muscles, high levels of 
discomfort and increased physical load on other than the exoskeleton’s target body parts, and true 
impact on potentially reducing injury prevalence (de Looze et al., 2015). 
Overall, exoskeletons need to be tested in highly controlled situations, because many practitioners 
see exoskeletons as a chance to optimize ergonomic work design. One way to test exoskeletons is in 
laboratory studies, evaluating their direct influence on the wearer and the work performance. 
Recently, the passive upper-body exoskeleton Laevo® has been studied in detail (Laevo®, Delft, the 

 
 
 
 
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Netherlands). Bosch et al. (2016) assessed the effect of wearing the Leavo® exoskeleton on the 
activity of the back muscles during trunk forward flexion and possible negative side effects for other 
muscles such as the abdominal and hip extensor muscles. They simulated an assembly task (10 work 
cycles of 20-30 s) and a static posture (endurance time up to 9 min) while the trunk was in 40° 
forward flexion. The tasks were performed with and without wearing the Laevo® exoskeleton. As 
expected, the lower back muscle activity decreased in both tasks with 35-44%. Additional 
measurements showed that the muscle activity decreased in the upper back with 44-50% and in the 
hip extensor with 20-24%. The activity of the abdomen muscles did not change when wearing the 
Laevo®. Despite these considerable decreases in muscular activity, the perceived discomfort in the 
chest increased, because this is the place where the exoskeleton exerts pressure to the body. Bosch 
et al. (2016) also observed that users wearing the Laevo® exoskeleton tend to overstretch their 
knees. This overstretch may be due to the pressure of the chest pads on the body, which pushes the 
upper body backward and hampers knee flexion. 
The study of Bosch et al. (2016) is a good first step to map the operation of the system and its effects 
on the physical load of the user. The results are promising with respect to muscular activity at the 
upper body, but unclear is what happens to the compression forces of the knee, what happens to the 
user’s posture during dynamic work tasks, and what happens to the physical load when the user is 
diverting from the symmetry line (sagittal plane) while bending. This information is necessary to 
assess the influence of this exoskeleton on the body, prior to a field feasibility study and its long-term 
implementation and use in the field. 
 
 

 
 
 
 
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3 
Objectives 
This study has three objectives: 
1. Assess to what extent wearing the Laevo® exoskeleton (with vs. without) changes knee 
compression force, reduces muscular load on the back muscles, changes muscular load on 
other body parts such as the legs and shoulders, and changes discomfort in different tasks 
(static vs. dynamic) and different postures (trunk flexion vs. trunk flexion and rotation). 
2. Estimate internal loadings on the spine, using a lumbar spine model, and see what the 
influence is of wearing the Laevo® exoskeleton. 
3. Assess the performance of subjects during functional activities (e.g., stair climbing) when 
wearing the Laevo® exoskeleton (with vs. without). 
 
 

 
 
 
 
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4 
Study design and study population 
4.1 
Study design 
4.1.1 Independent variables 
In the study, three independent variables will be investigated: 
- 
Exoskeleton: with vs. without; 
- 
Task: static vs. dynamic; 
- 
Knee angle: flexed vs. extended (only for the dynamic task) 
- 
Working posture: straight lifting/bending vs. lifting/bending with left/right trunk rotation. 
4.1.2 Outcomes 
In each experimental condition, the following 
outcomes will be assessed: 
- 
Muscular loading; 
- 
Knee joint loading; 
- 
Force on legs and chest due to the 
exoskeleton’s pads; 
- 
Performance on functional tests; 
- 
Subjective rating of perceived 
discomfort; 
- 
Participant evaluation of the 
exoskeleton; 
- 
Spinal loading. 
4.2 
Study population 
We will select healthy, male participants in 
the age of 18-40 years old. For the main 
experiment, we constructed a single Williams 
design (Bate and Jones, 2006) based on three 
independent variables with two levels each 
that resulted in six different orders of 
conditions (Figure 1A). The single Williams 
design corrects for possible first-order carry-
over effects. Using the results published by 
Bosch et al. (2016), we estimated the sample 
size including only the comparison of with 
and without Laevo® exoskeleton. Based on 
the reported outcomes of back discomfort, 
we estimate a sample size of 29 subjects. 
Combining both calculations, we strive to 
include a multiply of the single Williams 
design, i.e. a multiple of six, which would be 
30. However, we prefer to include 6x6 
 
Figure 1A. The single 6×6 Williams design, based on a 
balanced, uniform cross-over design. 
 
Figure 1B. The single 4×4 Williams design, based on a 
balanced, uniform cross-over design. 
 
Figure 1C. The double 3×3 Williams design, based on a 
balanced, uniform cross-over design.
1
2
3
4
5
6
1
A
B
F
C
E
D
2
B
C
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D
F
E
3
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D
B
E
A
F
4
D
E
C
F
B
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5
E
F
D
A
C
B
6
F
A
E
B
D
C
Subject
Period
1
2
3
4
1
A
B
D
C
2
B
C
A
D
3
C
D
B
A
4
D
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B
Subject
Period
1
2
3
1
A
B
C
2
B
C
A
3
C
A
B
4
C
B
A
5
A
C
B
6
B
A
C
Period
Subject

 
 
 
 
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subjects, leading to a number of 36 subjects (Attachment 1). The order of the three working 
positions (forward trunk flexion vs. left trunk rotation vs. right trunk rotation) will be randomized 
separately, using a double Williams design, i.e. 6 different orders. 
For the additional postural angle and weight measurements that will be performed in a full-factorial 
design, we will measurements consisting of exoskeleton status (with or without Laevo®), knee angle 
(flexed, extended), static trunk forward flexion angle (0°, 30°, 60°, 60°, 30°), and carried weight (0kg, 
8kg, 16kg). The conditions will be offered in a randomized order, based on the two independent 
variables exoskeleton status and knee angle, generated by a single Williams design with four 
different orders (Figure 1B). The static trunk flexion angles are always performed in ascending and 
descending order, i.e. 0°, then 30°, then 60°, then 60°, then 30°, which does not need randomization. 
The order of the three carried weights will be randomized separately, like the working positions, i.e. 
by using a double Williams design leading to 6 different orders (Figure 1C). 
For the additional functional tests, which are three (i.e., Stair Climb Test [SCT], Timed Up-and-go Test 
[TUG], course) and always performed in the same order, we randomized by exoskeleton status by 
drawing lots. 
4.3 
In- and exclusion criteria 
4.3.1 Inclusion criteria 
- 
Age between 18 and 40 years; 
- 
Male; 
- 
BMI < 30 kg/m2; 
- 
The participant will give his voluntary informed consent after receiving oral and written 
information of the content and goal of the study. 
4.3.2 Exclusion criteria 
- 
Aged <18 and >40 years; 
- 
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. 

 
 
 
 
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4.4 
Recruitment 
Subject will be recruited by means of asking fellow colleagues / students in Tübingen to voluntary 
study participation. When necessary, additional announcement e-mails will be sent to employees / 
students from the University and Hospital of Tübingen (UKT), and to former subjects who agreed to 
be informed about future studies (Attachment 2), emphasizing the voluntary principle.

 
 
 
 
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5 
Timetable 
The project has three overarching work packages (WP; Table 1), each containing a number of smaller 
work packages. The complete duration of the project is 14 months, with study start in July 2018, 
which includes preparations for the Ethical Committee. 
Table 1. The timetable in months for the proposed study that is intended to start in July 2018. Numbers represent the work 
package (WP) and letters represent the smaller sub-work package. 
Year 
2018 
2019 
Month 
Jul 
Aug 
Sep 
Oct 
Nov 
Dec 
Jan 
Feb 
Mar 
Apr 
May 
Jun 
Jul 
Aug 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1B 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1D 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1E 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1F 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1G 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1H 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2B 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2D 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2E 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2F 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2G 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2H 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3B 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3D 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3E 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3F 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3G 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.1 
WP 1: static work tasks 
This WP runs over the complete 14-month duration of the project, including ten smaller WPs. The 
WP starts with the design of the study design (A), followed by some pilot measurements (B). When 
the final study design is set, subjects will be recruited (C) who will perform the experiment (D). 
During data collection, a preliminary analysis (E) will be performed to get insights into data analyses 
and provide the project partners with an interim report. At the end of data collection, the main 

 
 
 
 
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analyses (F) will be performed, which are needed to evaluate the data and prepare them for 
publication (G). At the beginning of the project, the experimenters should make sure that all 
equipment is available or bought (H) and that there is a procedure to pay the participants (I). Along 
the project, the complete project team will meet a couple of times (J) and some money is reserved to 
visit national and international conferences (J). 
5.2 
WP 2: dynamic work tasks 
This WP runs exactly parallel to WP 1, because the experiment will be designed so that all 
participants perform a combination of one static and one dynamic simulated work element. This 
means that the same subset of smaller WPs accounts in the same way as for WP. 
5.3 
WP 3: lumbar spine model 
This WP is performed not by the Institute of Occupational and Social Medicine and Health Services 
Research, but by the research cluster Simulation Technology of the group Biomechanics and 
Biorobotics as part of the University of Stuttgart. As in the other two WP’s, this WP also relies on 
measurement data, meaning that input for the modelling is considered both in the development of 
the study design (A) and during the pilot measurements (B). The model of the lumbar spine already is 
available, but needs to be adjusted so that information of the Laevo® exoskeleton can be 
incorporated (C). When data collection has started, the collected data can be used to improve and 
validate the model (D). As for WP 1 and WP 2, the appropriate equipment has to be available or 
bought (E), participants should receive a refund (F), and knowledge gained during this project will be 
shared with the project team (G) and with colleague scientists at national and international 
conferences (G). 
 
 
 

 
 
 
 
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6 
Study procedure 
6.1 
Experimental tasks 
In preparation to the measurements, we determined the details of the static and dynamic tasks in 
combination with the trunk angles. The static task will mimic bimanual sorting in a 40° forward bent 
position or a 40° forward bent position with 45° left or right rotation of the upper body (Figure 2). 
The working distance and working height will be calculated by the individual’s body segment lengths, 
the given forward trunk flexion angle of 40°, the resulting shoulder angle of 40° (holding the upper 
arm orthogonal to the bas), and a defined elbow angle of 135°, counted from the base below the 
ankle position. The working distance to the side is ~20 cm also counted from the position of the 
ankle. The static tasks will be performed for 1.5 min in each position, with a passive break of 30 s in 
between successive positions (total duration is 4.5 min, Figure 2B). In between consecutive blocks 
(i.e., exoskeleton status and knee angle), participants get a passive break of ~2 min. This procedure is 
repeated two times for exoskeleton status (with vs. without), lasting ~11 min in total. 
 
Figure 2. (A) The static task performed in three positions: trunk forward flexion (left), trunk forward flexion with rotation to 
the left (middle), and trunk forward flexion with rotation to the right (right). (B) The timeline for each exoskeleton status 
(with vs. without), within which three working postures are measured, separated by 30-s passive breaks. 
The dynamic task will mimic a bimanual box replacing task in a 70° forward bent position or a 70° 
forward bent position with 45° rotation of the upper body (Figure 3A). The box handled will be ~10 
kg with grips on both short sides, holding an arm angle of 135°. The working distance to the front is 
~50 cm and to the side ~50 cm counted from the position of the ankle. The dynamic task will be 
performed as follows: the box has to be taken from the height of the bending position (70°), moved 
to an upright standing position, and placed back in bending position (70°) without or with rotation 
sideward. The dynamic task will be performed in two series of 5 repetitions in each working posture 
(forward trunk flexion, trunk rotation to the left, trunk rotation to the right), lasting 25 s per 
repetition, with a 35-s passive break s after each series of 5 repetitions and a 60-s passive break after 
each working position (total duration is 6.5 min). In between consecutive blocks (i.e., exoskeleton 
status and knee angle), participants get a passive break of ~3 min. This complete procedure (Figure 
3B) is repeated four times for exoskeleton status (with vs. without) and knee angle (flexion vs. 
extension), all in all lasting ~35 min. 

 
 
 
 
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Figure 3. (A) The dynamic task performed in three positions: trunk forward flexion (left), trunk forward flexion with rotation 
to the left (middle), and trunk forward flexion with rotation to the right (right). (B) The timeline for a combination of 
exoskeleton status (with vs. without) and knee angle (extended vs. flexed), within which three weights are handled, 
separated by 60-s passive breaks. 
6.2 
Modelling of the lumbar spine 
A lumbar spine model has been developed by the research group “Biomechanics and Biorobotics” of 
the research cluster “Simulation Technology (SimTech)” of the University of Stuttgart, which can 
predict internal forces during flexion movements (Rupp et al., 2015). The structure and properties of 
the model are outlined in Figure 4, which includes a detailed lumbar spine with non-linear discs, 
ligaments, and muscles. 
 
Figure 4. Model of the lumbar spine (Rupp et al., 2015). 
With the lumbar spine model, we aim to investigate how internal forces in the lumbar spine change 
as a result of external forces of an exoskeleton during trunk flexion. This is the first time that an 

 
 
 
 
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exoskeleton is coupled to a detailed biomechanical model of the lumbar spine. We will also try to 
elaborate the modelling of the static task elements in trunk flexion and rotation by additional 
analyses of dynamic trunk flexion movements. 
6.3 
Static trunk forward flexion angle while holding a load 
From a technical point of view, we are interested in the natural relationship (i.e. without Laevo®) 
between the spinal angle and the muscular stress on the back muscle (e.g., M. erector spinae 
longissimus lumbalis). In addition, we are interested how this relationship changes when subjects are 
wearing the exoskeleton, and when carrying different loads. Participants will perform a set of twelve 
different tests, which are a combination of exoskeleton status (two levels: without vs. with Laevo®), 
knee angle (extension vs. flexion), static trunk forward flexion angle (five levels; 0°, 30°, 60°, 60°, 30°), 
and load carried (three levels; 0kg, 8kg, 16kg). The trunk flexion angles will be performed in 
succession, meaning that a person will start upright (0°), slowly and uniformly move towards a slight 
forward flexion (30°), slowly and uniformly move in a deeper forward flexion (60°), go deeper and 
slowly and uniformly move back to the deep forward flexion (60°), and slowly and uniformly move 
back into a slight forward flexion (30°) (Figure 5A). Using a full-factorial design with the independent 
variables exoskeleton status and knee angle, participants will perform a total of four blocks. Within 
each block, the load carried is performed for the trunk flexion angles, lasting ~30 s. In between 
consecutive conditions within a block (i.e., carried weight), participants get a passive break of ~30 s 
(total duration is ~2.5 min). In between consecutive blocks (i.e., exoskeleton status and knee angle), 
participants get a passive break of ~3 min. This procedure is repeated four times for exoskeleton 
status (with vs. without) and knee angle (extended vs. flexed), all in all lasting ~20 min (Figure 5B). 
 
Figure 5. (A) Different trunk forward flexion angles while holding different loads, performed with and without the Laevo® 
exoskeleton, with extended and flexed knees, while holding loads of 0kg, 8kg or 16kg. (B) The timeline for a combination of 
exoskeleton status (with vs. without) and knee angle (extended vs. flexed), within which three trunk flexion angles are 
measured in ascending and descending order, separated by 30-s passive breaks. 
The arms will always be extended, and the weight will be bimanually carried, meaning that the total 
weight (8kg and 16kg) will dividing over both hands (2×4kg and 2×8kg). The participant will receive 
direct visual feedback on a monitor of the trunk flexion angle. 

 
 
 
 
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6.4 
Functional tasks 
Functional tests are usually used for patients and elderly to estimate their level of performance. We 
use a small selection of available functional tests to see how participants perform with and without 
wearing the Laevo® exoskeleton. The following three tests are selected, each of which has its own 
outcome with interpretation: 
1. Stair Climb Test (SCT): ascend and descend an isolated set of 5 or 9 stairs (18 cm) using a 
single handrail is measured (Bennell et al., 2011)); 
a. Outcome: time (seconds) taken to complete the number of steps negotiated; 
b. Interpretation: smaller values represent better performance, and number of steps 
negotiated in set time, where larger values represent better performance. 
2. Timed Up & Go (TUG): assessment of a basic mobility skill (Bennell et al., 2011). The subject 
is sitting on a regular chair with arm rests, rises from the chair, walks 3 m to the front, turns, 
walks back to the chair, and sits down. The subject is wearing regular footwear (Bennell et 
al., 2011; Dobson et al., 2013); 
a. Outcome: time (s) taken to rise from a chair, walk 3 m, turn, walk back to the chair, 
then sit down; 
b. Interpretation: smaller values (faster time) represent better performance. 
3. Course: containing three different work station simulations; (A) a static screwing task in a 40° 
trunk flexion angle; (B) a dynamic logistic pick-and-place task replacing boxes from one side 
to another; (C) a dynamic lifting task moving objects from a grid box to a table. 
a. Outcome: time (s) taken to complete the course three times after another without 
any breaks and heart rate (Hz) will be continuously recorded; 
b. Interpretation: smaller time values (faster time) represent better performance; 
smaller heart rate values represent less strain. 
The functional tests are performed in a predefined order: (1) SCT, (2) TUG, (3) course. The order of 
exoskeleton status will be randomized by drawing lots. For the SCT and TUG tests, the exoskeleton 
will be worn but turned off; for the course the exoskeleton will be worn and turned on. 
6.5 
Experimental procedure 
Participants will visit the work physiology laboratory at the Institute of Occupational and Social 
Medicine and Health Services Research two times. During the first visit, the participants will be 
officially included in the study after they have read the general information (Attachments 3), have 
signed the informed consent form (Attachment 4), and have met the eligibility criteria (Attachment 
5). When the participant is included, he will be familiarized with the Laevo® exoskeleton, the 
simulated static and dynamic assembly tasks, and the functional tests. Finally, the participant will fill 
out two short questionnaires providing some general information (Attachment 6) and information 
about his history of musculoskeletal complaints (Attachment 7). The first visit will take ~1 hour. 
During the second visit, the participants will perform the experiment, taking ~4 hours in total. The 
study procedure is displayed in Figure 6. First, participants will be prepared with the measurement 
equipment, i.e. electrodes will be placed to record muscle activity and heart rate and position 
sensors to record postures and movements. After preparation, the participants have to perform 
reference measurements to normalize the recordings of muscle activity (electromyography; EMG) 

 
 
 
 
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and to correct the possible systematic error in the recordings of the body posture. The experiment 
consists of three phases: first, the participants will perform the six experimental conditions (with vs. 
without Laevo®, static vs. dynamic, knees extended vs. knees flexed); second, the participants will 
perform the twelve angle-force conditions, grouped into four blocks (with vs. without Laevo®, knees 
extended vs. flexed); third and last, the participant will perform the three functional tests. In 
between each of these three sets of measurements, the participant will have a passive break of 5 min 
and is allowed to drink or eat. After the static and dynamic tasks, participants are asked to fill out a 
questionnaire (combination of NASA-TLX and self-developed questions; see Chapter 7.9). After all the 
measurements are finished, the participants are asked to fill out a final questionnaire evaluating the 
usability of the Laevo® exoskeleton (combination of SUS, TUI and self-developed questions; see 
Chapter 7.9). 
 
Figure 6. The experimental protocol is presented along with a timeline (min). Note that the main experimental conditions 
are displayed in red boxes and the functional tests in blue boxes. The order of both sets is randomized across participants as 
described previously. The test to determine the relation between postural angle and muscular stress is displayed in a black 
box, which will also be performed in a randomized order. The yellow boxes represent the start and end of the complete 
experiment, i.e. preparing and tidying up the participants. 
6.6 
Output 
The collected data will be analyzed and prepared for statistical analyses if possible. All results will be 
presented to the cooperation partners in workshops and/or interim and final reports. In addition, the 
results will also be presented at symposia (e.g., annual GfA-congress, annual DGAUM- congress, 
annual FAP- congress) and published in peer-reviewed international journals (e.g., triennial PREMUS-
congress, triennial IEA-congress, triennial ICOH-congress), to make the results accessible to the 
scientific community. 
 
 

 
 
 
 
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7 
Measurement methods and analyses 
7.1 
General data 
At the first visit to the laboratory, participants have to fill out the Standardized Nordic Questionnaire 
(Nordic Musculoskeletal Questionnaire) to provide us with information about their musculoskeletal 
history and some basic anthropometrics, including age, sex, body height, and body weight 
(Attachments 6 & 7). 
7.2 
Muscle activity 
The Laevo® exoskeleton aims to reduce the physical load on the back of the wearer, but it might 
influence the physical load to other body parts such as the shoulders and legs. To record the activity 
of selected muscles at all these body parts (Table 2), we will use surface EMG. This method uses 
recording electrodes (4224 mm, KendallTM H93SG ECG Electrodes, Covidien, Zaltbommel, the 
Netherlands) that are attached to the skin’s surface overlaying the muscle of interest with an inter 
electrode distance (IED) of 26 mm. The differential signal (bipolar derivation) of two electrodes 
placed over one muscle belly recorded by an amplifier (PS12, THUMEDI® GmbH & Co. KG, Thum-
Jahnsbach, Germany), gives a firm estimation of that muscle’s electrical activity in microvolts (µV). 
This electrical activity pattern enables us to estimate the magnitude of the muscle activity 
(amplitude) and the overall firing frequency of the muscle (power frequency). The amplitude can be 
calculated by the overall root-mean-square (RMS) of the power spectrum of the EMG signal. The 
median power frequency (MPF) can be calculated as the median of the power spectral density of the 
EMG signal. 
7.3 
Kinematics: posture and force 
Combining ground reaction forces with linear segment accelerations and joint angles (and their 
derived angular acceleration) enables the estimation of compression forces and force moments in 
joints. Our joint of interest is the knee, of which we will estimate the compression forces and force 
moments during the forward bent situations; the situations in which there is strong trunk rotation, 
estimations may become inaccurate and unreliable. Several approaches exist to estimate joint forces 
and joint moments, including forward dynamics, static body analyses, and inverse dynamics. We will 
use inverse dynamics to estimate the forces and moments around the knee, for which we need the 
(1) position of the lower and upper legs, (2) the ground reaction forces below the feet, (3) the 
angular accelerations of the ankle and knee joints, and (4) segment parameters like segment length, 
segment weight, and segment moment of inertia. 
For the position, we will use position sensors that are integrated in modules of the PS12 system 
(Thumedi® GmbH & Co. KG, Thum-Jahnsbach, Germany). The position sensors will be placed on the 
lower leg, upper leg, and back providing us with the position in flexion and lateral flexion angles each 
of the three segments. 
Ground reaction forces below the feet will be recorded using a force plate (Bertec 3D-
Kraftmessplatte FP9090-15-1000, Velamed GmbH, Köln, Germany) with digital amplifier (Bertec, 
AM6500, Velamed GmbH, Köln, Germany). The segment parameters will partly be measured 
(segment lengths) and partly be estimated (segment weights and moments of inertia) using the four 
summary tables as provided by Krishnan et al. (2016). 

 
 
 
 
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Table 2. Six muscles of interest with a description of the posture and force level of their reference voluntary contraction 
(RVC) and maximal voluntary contraction (MVC). The RVC will be performed once for ~10 s, with 1-min rest intervals in 
between contractions of the same muscle and no rest in between RVCs and MVCs of different muscles. 
Segment 
Muscle 
Reference voluntary contraction 
Force level 
Lower 
leg 
M. gastrocnemius 
medialis 
Stand upright, unilateral isometric maximum planter flexion 
contraction, i.e. going to the maximum / tip of the toes with full 
strength (MVC) (Rieman et al., 2011) 
Weight 
own body 
Upper 
leg 
M. vastus lateralis 
Lay prone, 90° knee flexion, foot neutral (90° ankle flexion), keep 
position while a rope with a weight hanging over a pulley was attached 
around the front-side of the ankle 
5 kg 
10 kg 
M. biceps femoris 
Lay prone, 90° knee flexion, foot neutral (90° ankle flexion), keep 
position while a rope with a weight hanging over a pulley was attached 
around the back-side of the ankle 
5 kg 
7 kg 
Lower 
back 
M. erector spinae 
longissimus lumbalis 
Lay prone, upper body and hips off the bench and extended legs fixed 
with straps, arms hang orthogonal to the ground below the shoulder. 
(1) Back (hip) extension without resistance (Abboud et al., 2014) 
(2) Back (hip) extension with 15-kg resistance 
(3) Back (hip) extension against fixed barrier (MVC) 
Weight own 
upper body 
(+ 15 kg) 
Abdomen 
M. rectus abdominis 
Lay supine, upper body and hips off the bench and extended legs fixed 
with straps, arms cross in front of the chest. 
(1) Back (hip) flexion without resistance 
(2) Back (hip) flexion with 10-kg resistance 
Weight own 
upper body 
(+ 10 kg) 
Shoulder/ 
neck 
M. trapezius 
descendens 
Stand upright; arms in 90° arm abduction and slightly in the frontal 
plane, elbows extended (not overstretched), holding a weight in each 
hand 
2×0 kg 
2×2 kg 
 
The angular accelerations can be derived from joint angles, which we will record using position 
sensors that are also integrated in modules of the PS12 system (Thumedi® GmbH & Co. KG, Thum-
Jahnsbach, Germany). The position sensors will be placed on the foot, lower leg, and upper leg, 
providing us with the flexion and lateral flexion angles of each segment with respect to the earth’s 
radius of gyration. For joint angles, we can subtract one segment angle from another. In addition, we 
will also record position of the spine by placing one sensor at the fifth lumbar vertebra (L5) and one 
at the third thoracic vertebra (T3). 
For the inverse modeling calculations, we will use a 2D model in which joints are represented as 
hinges and segments as rigid bodies (Figure 7). We are interested in the net moment of the upper leg 
around the lower leg (,	 in Figure 7) and the force of the upper leg acting on the lower leg (
⃗,	 in 
Figure 7). 
The contact pressure between the Laevo® exoskeleton as exerted on the chest will be measured 
using a Ø38 mm × 10 mm force sensor (Type KM38, ME-Meßsysteme GmbH, Henningsdorf, 
Germany) that will be integrated in the chest pad. 

 
 
 
 
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Figure 7. Illustrative inverse dynamic segment model of the lower leg and foot (left) with a sketch of the free body diagrams 
of the foot (middle) and lower leg (right). The symbols represent kinematic parameters: ankle (), knee (), center of mass 
of the foot (
), center of mass of the lower leg (	), flexion angle of the lower leg (	), ground reaction force (
⃗,
), force 
of the lower leg acting on the foot (
⃗	,
), force of the foot acting on the lower leg (
⃗
,	), force of the upper leg acting on 
the lower leg (
⃗,	), gravitational force of the foot (⃗
), gravitational force of the lower leg (⃗	), net moment of lower leg 
around foot (	,
), net moment of foot around lower leg (
,	), and net moment of upper leg around lower leg (,	). 
7.4 
Reference measurements 
A reference posture will be recorded while the subject is standing upright with his back straight 
against a vertically levelled wall, his arms alongside his body, and his hand palms facing forward. The 
angles from this recording all represent zero angles, and will be used to correct the experimental 
recordings for any systematic offsets. 
EMG is recorded in microvolt (µV) and may vary considerably between subjects. For this reason, we 
will normalize the activity of all measured muscles to a reference voluntary electrical activity (RVE) 
assessed during reference voluntary contraction (RVC; Table 2). During the reference contraction, 
the experimenter encourages the subject to stay in the reference posture. Each reference 
contraction will take ~10 s and will be performed once, of which the most stable 5-s plateau of one of 
the contractions will be used for EMG normalization and referred to as percent reference voluntary 
electrical activity (%RVE; Mathiassen et al., 1995). The reference measurements take ~30 min in 
total. 
7.5 
Heart rate 
The heart rate will be continuously recorded by electrocardiography (ECG) using ECG recording 
electrodes (4224 mm, KendallTM H93SG ECG Electrodes, Covidien, Zaltbommel, the Netherlands). 
The two electrodes will be attached to the skin’s surface, placed ~5 cm cranial and ~3 cm left-lateral 
from the distal end of the sternum and over the anterior to midaxillary line at the fifth left rib. The 
heart rate signal will be recorded by the same amplifier as EMG (PS12-UD, THUMEDI® GmbH & Co. 
KG, Thum, Germany). 
7.6 
Discomfort 
Participants will rate their overall subjective feeling of discomfort (RPD) on an 11-point numerical 
rating scale (McCaffery and Beebe, 1989) (Attachments 8 & 9), ranging from 0 (no discomfort at all) 
to 10 (maximally imaginable discomfort). When participants experience a feeling of discomfort > 0, 
we ask them to define the body region (Kuorinka et al., 1987) causing this sensation. 

 
 
 
 
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7.7 
Functional tests 
To assess how wearers of the Laevo® can walk around and use the exoskeleton in between work 
tasks, a set of two functional tests will be assessed by measuring time duration and/or difficulty 
and/or on an 11-point numeric rating scale. For each functional test, the outcome(s) to be recorded 
is listed below: 
1. Stair Climb Test (SCT): time (s) taken to complete the number of steps negotiated (Bennell et 
al., 2011); 
2. Timed Up & Go (TUG): time (s) needed to rise up from the chair, walk, turn, and sit back 
down on the chair again (Dobson et al., 2013). 
3. Course: time (s) needed to complete the course and average heart rate (Hz) over the course. 
7.8 
Relation static trunk forward flexion angle, carried load and 
muscular stress / spinal load 
With the data collected from the twelve tests that last ~30 s, we will be able to draw curves for every 
load carried across different trunk forward flexion angles. These curves will provide us with 
information whether the relation between increased trunk forward flexion is linear or not with 
respect to outcomes such as muscular activity of the lower back muscle (i.e., M. erector spinae 
longissimus lumbalis) or the abdomen muscle (i.e., M. rectus abdominis). In addition, separate lines 
within these graphs account for exoskeleton status (with vs. without exoskeleton), knee angle 
(extension vs. flexion) and weight carried (0kg vs. 8kg vs. 16kg), during which the relation between 
the trunk flexion angle and the muscular activity level could change too. 
7.9 
Participant evaluation 
To evaluate the workload of the complete set of experimental conditions, we will use the NASA-TLX 
(Hart and Staveland, 1988; Attachment 10), which assesses six dimensions of workload (i.e., mental 
demand, physical demand, temporal demand, own performance, effort, and frustration). Subjects 
will rate only three of these dimensions on a scale from 0 to 100 (physical demand, temporal 
demand, and effort). We will assess overall partial workload by averaging or adding the scores of the 
three dimensions (Hoonakker et al., 2011). In addition, we will analyze the scores of the subscales 
(Hart, 2006; Hoonakker et al., 2011). Next to the NASA-TLX, we will also ask eight self-developed 
questions (Attachment 10). 
To evaluate participants view on the usability and acceptance of the Laevo® exoskeleton in the 
performed tasks and on the acceptance of the Laevo® exoskeleton in work settings, we will ask six 
self-developed questions, use the ten questions of the standardized and validated questionnaire 
System Usability Scale (SUS), and use a selection of seven questions from the standardized 
Technology Usage Inventory (TUI) from the domains usability (n = 3) and skepticism (n = 4). The final 
set of questions (n = 23; see Attachment 11) will take approximately 10 minutes. 
The SUS is a quick and easy to use method to collect the usability evaluation of users of a system 
(Borsci et al., 2009), in this case the system is the Laevo® exoskeleton. The SUS is also seen as a tool 
to measure the subjective perception of interaction with a system (Brooke, 1996). The SUS is 
recommended as satisfaction metric to complement other performance metrics such as time on task, 

 
 
 
 
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which in this study is done with the functional tests. The assessment of the SUS is the level of 
agreement on a Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree) (Brooke, 1996). 
The TUI is a questionnaire that can be used for research purposes or in the field of technology 
acceptance research (Kothgassner et al., 2013). It could support technique developers in the user-
centered evaluation of new technologies, such as virtual simulations. The TUI records technology-
specific and psychological factors that contribute to the actual use of the technology, containing the 
following eight scales: curiosity, anxiety, interest, usability, immersion, usefulness, skepticism, and 
accessibility. The TUI also includes the Intention to Use (ITU) scale, which contains three questions. 
The assessment of the TUI is the level of agreement on a Likert scale ranging from 1 (not true) to 7 
(true). From the original TUI, we will only include the questions from the domains usability (n = 3) 
and skepticism (n = 4). 
7.11 Statistical analysis 
This study aims to answer the research question “what is the influence of exoskeleton, task, and 
posture on muscular activity, knee joint loading, spinal loading, and discomfort?”. Using a within-
subject design, i.e. a randomized, balanced cross-over design, the data should be analyzed using a 
repeated-measures analysis of variance (ANOVA). This model contains three independent, within-
subject factors: exoskeleton (with vs. without), posture (forward bend vs. rotation), and task (static 
vs. dynamic). The outcome parameters include muscular activity (i.e. RMS of EMG) of the selected 
muscles (Table 2), knee compression force, spinal loading, and discomfort. We will use JMP software 
(JMP® 13.1.0, SAS Inc., Cary, NC, USA) or SPSS software (IBM® Statistics® 25.0, Armonk, NY, USA) to 
perform the repeated measures ANOVA and accept statistical significance for p < 0.05. 
The outcomes of the functional tests are based on numeric rating scales and / or are time-related, 
and will be statistically evaluated using a paired T-Test to compare the conditions with and without 
Laevo®. The results from the tests combining exoskeleton with trunk forward flexion angle and with 
load carried will be plotted to see if the relationship between the trunk forward flexion angle (x-axis) 
and the muscular stress of the erector spinae muscle (y-axis) changes per load carried (different 
lines) and exoskeleton (with vs. without; different lines). 
The relationships between static trunk forward flexion angle and muscular activity will be assessed 
using regression analysis and compared between different loads carried (while keeping the 
exoskeleton status constant) and between exoskeleton statuses (while keeping the carried load 
constant). 
The results of the two questionnaires that evaluate the acceptability and usability of the Laevo® 
exoskeleton will be narratively discussed. 
 
 

 
 
 
 
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8 
Risk for the participant 
The experiment has no threatening risks for the participant and all measurement equipment is 
certified in declarations of conformity (Attachments 12-16). Note that there can be some side-effects 
of study-related procedures about which we will inform the participant, including: 
- 
Skin irritation or reddening due to skin preparation and of the attachment of the adhesive 
electrodes; in rare cases, participants may experience allergic reactions; 
- 
When the electrode cables are tights and pull the skin, participants could experience tingling 
or tension sensations in the area of the adhesive electrodes due to this cable pull; 
- 
Sensations of tension or muscle fatigue along the duration of the experiment; 
- 
Due to participants performing the experiment have to stand during the measurements, it 
might occur that participants experience possible sensations of dizziness, loss of blood 
pressure, and a very low risk of impotence due to the ~60-min periods of interrupted 
standing; 
- 
Minor risk of muscle aching the day after the experiments due to maximum voluntary muscle 
contraction. 
 
 
 

 
 
 
 
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9 
Data protection 
The participants as well as their personal and recorded data will be numerically pseudonymized by 
assigning a randomly generated two-digit identification number to the examined participant (e.g., 
S30P_ _). Relating analyzed outcome data to the natural person is only possible by inspection of the 
decoding list. This list, together with the informed consents of all volunteering participants, will be 
stored separately from the measured data in the storage of the Institute of Occupational and Social 
Medicine and Health Services Research. All participant data will be stored for a period of ten years 
after publication of the results. The destruction of the data in paper form is carried out by means of 
the disposal boxes for data protection at the University Hospital, and the destruction of the data in 
electronic form is carried out by means of transferring the data off the memory cards of the devices. 
The measurements as part of this proposal are all recorded on portable computers that are 
accessible by means of a password only and cannot be accessed by any network. The pseudonymized 
data are processed within the University Hospital (UKT) network, of which the time of the 
measurement collection is removed from the operating software whenever possible. The measuring 
devices are configured identically for all measurements to exclude a possible association between 
the measurement configuration and the participants. After completing the data analysis, the data of 
the participants are stored together with the photo documentation on Blu-ray discs. 
Only employees directly involved in the study have access to the data. In addition, all employees of 
the Institute for Occupational and Social Medicine and Health Services Research who are involved in 
the study are subject to medical confidentiality. 
At the start of the study, participants are asked whether they wish to be informed about the primary 
results of the study. In case of several interested parties, an information event will be organized for 
the participants after completion of the data evaluation. If there is only little interest, a brief written 
presentation of the primary results will be spread and sent to interested parties by e-mail. 
 
 
 

 
 
 
 
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10 
Study finance 
The financing of the study, including personnel costs and facility costs for technical equipment and 
assistance, are funded by several industrial companies (Table 3). The study participants will receive a 
compensation of about € 10 per hour. The familiarization day is without refund, the testing day will 
take approximately 4 to 5 hours, which results in a total amount of € 45. 
Table 3. Funding of the project is divided over eight partners, although not every partner collaborates in every work 
package. 
Work package
Partner 
WP 1 
Static task element 
WP 2 
Dynamic task element 
WP 3 
Lumbar spine modelling 
Daimler AG 
 
 
 
AUDI AG 
 
 
 
BMW AG 
 
 
 
MTU Aero Engines AG 
 
 
 
Iturri Gruppe 
 
 
 
Deutsche Post AG 
 
 
 
BASF 
 
 
 
Dachser Intelligent Logistics 
 
 
 
 
 
 

 
 
 
 
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11 
Personnel Staff 
In work packages (WP) 1 and 2, employees from the Institute of Occupational and Social Medicine 
and Health Services Research of the University Hospital Tübingen & University of Tübingen will be 
responsible for each of the steps. In WP 3, all the modelling work is done by the group Biomechanics 
and Biorobotics of the cluster Simulation Technology (SimTech) of the University of Stuttgart. 
11.1 Work packages 1 & 2 
The main contributors to these two work packages are: 
- 
Benjamin Steinhilber (15% of 100%-employment = 15%) 
o Project leader: responsible for the study design, data interpretation; 
- 
Tessy Luger (15% of 100%-employment = 15%) 
o Project leader: responsible for the study design and supervising the following stages 
of the study; 
- 
Robert Seibt (100% of 65%-employment = 65%) 
o Technician and researcher: responsible for study design, measurement equipment, 
pilot and final measurements, data analysis, and data interpretation; 
- 
Marlene Röttgen (6.7% of 75%-employment = 5%) 
o Project management; 
- 
PhD student, Mona Bär (100% of 65%-employment = 65%) 
o Preparing, performing, analyzing and interpreting measurements. 
11.2 Work package 3 
- 
Benjamin Steinhilber (15% of 100%-employment = 15%) 
o Project leader: responsible for the study design, data interpretation; 
- 
Tessy Luger (15% of 100%-employment = 15%) 
o Project leader: responsible for the study design and supervising the following stages 
of the study; 
- 
Marlene Röttgen (6.7% of 75%-employment = 5%) 
o Project management; 
- 
PhD student, Mona Bär (100% of 65%-employment = 65%) 
o Model building and validation. 
 
 
 

 
 
 
 
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11 
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