Comfort During Prolonged Exposure to Repetitive Forces Mimicking Exoskeleton Use
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Sponsor
- Enrollment
- 15
- Locations
- 1
- Primary Endpoint
- Perceived discomfort as indicated on a 10 mm visual analog scale (VAS) by the participants, ranking from 'no discomfort' to 'worst imaginable comfort' (10)
Study Overview
Brief Summary
Exoskeletons can be used for rehabilitation, as assistive device for patients, or to support workers during strenuous tasks. To fulfil their purpose, they need to apply forces to the user's musculoskeletal system. The forces are transmitted at skin level through an interface, often in the form of cuffs. Adverse events causing discomfort and injuries to the skin and underlying tissue can be attributed to those interaction forces. While there is some information about safe limit values for impact forces or pressure and shear applied for short durations, little is known regarding comfort and safety thresholds for repetitive forces applied over long durations as is the case in exoskeleton use. This study therefore aims at gaining new knowledge on safe and limit values, based on discomfort (staying below pain threshold), for continuous repetitive shear and normal forces applied through a cuff.
Therefore, the primary objective is to determine comfort thresholds for prolonged exposure to repetitive normal and shear stress exerted to the human thigh via a cuff with straps, using different force patterns comparable to those exerted during exoskeleton use. The secondary objectives are to determine the feasibility of the experiment, the influence of subject characteristics on comfort thresholds, the occurrence of skin injuries or other negative signs, and whether characteristics of muscle activity can be related to discomfort.
Detailed Description
Rationale: Exoskeletons can be used for rehabilitation, as assistive device for patients, or to support workers during strenuous tasks. To fulfil their purpose, they need to apply forces to the user's musculoskeletal system. The forces are transmitted at skin level through an interface, often in the form of cuffs. Adverse events causing discomfort and injuries to the skin and underlying tissue can be attributed to those interaction forces. While there is some information about safe limit values for impact forces or pressure and shear applied for short durations, little is known regarding comfort and safety thresholds for repetitive forces applied over long durations as is the case in exoskeleton use. This study therefore aims at gaining new knowledge on safe and limit values, based on discomfort (staying below pain threshold), for continuous repetitive shear and normal forces applied through a cuff.
Objective: The primary objective is to determine comfort thresholds for prolonged exposure to repetitive normal and shear stress exerted to the human thigh via a cuff with straps, using different force patterns comparable to those exerted during exoskeleton use. The secondary objectives are to determine the feasibility of the experiment, the influence of subject characteristics on comfort thresholds, the occurrence of skin injuries or other negative signs, and whether characteristics of muscle activity can be related to discomfort.
Study design: The study is a cross-sectional intervention study with one measurement session, where participants will provide a continuous comfort rating during exposure to repetitive normal and shear forces.
Study population: The aim is to include 20 healthy participants in total, matching the age groups 18-35 and 55-85.
Intervention: A pre-defined set of prolonged repetitive force patterns will be applied to each participant's thigh though a contact force which is similar to cuffs commonly used in gait exoskeletons. The forces will be applied by a custom made actuated test device and are based on normal use of exoskeletons.
Study Design
- Study Type
- Interventional
- Allocation
- Na
- Intervention Model
- Single Group
- Primary Purpose
- Other
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to 85 Years (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Between 18 and 35 or between 55 and 85 years of age
- •Able to provide informed consent
Exclusion Criteria
- •Unable to follow simple instructions
- •Insufficient knowledge of the Dutch or English language to understand the purpose and methods of the study
- •skin lesions at the thigh
- •sensory impairments
- •severe blood pressure fluctuations
- •inability to sit in required posture in experiment chair for 60 minutes
- •taking blood thinners or showing signs for increased bleeding tendency
Outcomes
Primary Outcomes
Perceived discomfort as indicated on a 10 mm visual analog scale (VAS) by the participants, ranking from 'no discomfort' to 'worst imaginable comfort' (10)
Time Frame: 80 minutes
The level of discomfort will be indicated on a VAS as a percentage of maximum imaginable discomfort through a slider that is positioned within reach of the subjects. It will be synchronized with the forces exerted in relation to time. The onset of discomfort, i.e. the point at which the slider of the VAS is first moved to a position \>0, is recorded as discomfort detection threshold (DDT). If the participant activates the enabling switch indicating that the force creates pain rather than discomfort, this point is recorded as pain detection threshold (PDT).
Secondary Outcomes
- Number of completed test sessions/dropouts(160 minutes)
- Occurrence of injuries or other negative signs(30 minutes)
- Surface Electromyography (EMG) recordings of Rectus femoris(120 minutes)