Comfort Thresholds for Repetitive Forces

NCT05347810 | Completed

• 1 other identifier: 80800
• Study Type: interventional
• Target: 15
• Locations: 1 country
• Sites: 1

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.

Conditions

Healthy

Keywords

Exoskeleton; Safety; Comfort; physical Human-Robot Interaction

Outcome Measures

Primary Outcomes (1)

• Perceived discomfort as indicated on a 10 mm visual analog scale (VAS) by the participants, ranking from 'no discomfort' to 'worst imaginable comfort' (10)

  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).

  80 minutes

Secondary Outcomes (3)

• 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

Other Outcomes (4)

• Height in meters

  2 minutes

• Body weight in kg

  2 minutes

• Age in years

  1 minute

Study Arms (1)

Study group

EXPERIMENTAL

All participants in the study will receive the same investigational treatment (application of prolonged repetitive forces) and provide continuous comfort ratings.

Other: Application of repetitive forces mimicking exoskeleton use

Interventions

Application of repetitive forces mimicking exoskeleton use OTHER

The investigational treatment consists of applying a predefined set of continuous and repetitive forces to the participant's thigh. It is applied using a custom device that has been designed specifically for this study. The forces to be applied are based on forces measured during exoskeleton use and will not exceed pain pressure thresholds reported in literature. The participants will hold an enabling switch at all times which they can activate to release the force exerted to their thigh. Alternatively, the experimenter can activate an emergency switch if the situation seems unsafe.

Study group

Eligibility Criteria

• Age: 18 Years - 85 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Between 18 and 35 or between 55 and 85 years of age
• Able to provide informed consent

You may not qualify if:

• 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

Sponsors & Collaborators

• Roessingh Research and Development: lead

Study Sites (1)

Roessingh Research and Development

Enschede, Netherlands

Location

Study Officials

• Gerdienke Prange, PhD

  Roessingh Research and Development

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: 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 Record Dates

• First Submitted: March 29, 2022
• First Posted: April 26, 2022
• Study Start: May 11, 2022
• Primary Completion: June 10, 2022
• Study Completion: June 10, 2022
• Last Updated: June 22, 2022

Record last verified: 2022-06

Data Sharing

• IPD Sharing: Will not share

Locations

NL (1)