optimal upper limb support conditions for mouse use? richard wells
Post on 15-Jan-2016
35 Views
Preview:
DESCRIPTION
TRANSCRIPT
Department of Kinesiology,University of Waterloo OPTIMAL UPPER LIMB SUPPORT
CONDITIONS FOR MOUSE USE?
Richard Wells
Department of Kinesiology,University of Waterloo
RationaleRationale
A number of recommendations for support of the mouse arm have appeared in the computer and RSI-related literature. These include: WRIST; planting the ventral surface of the wrist on the work surface and
moving the mouse from the wrist joint ELBOW; planting the elbow on the chair’s arm rest and moving the
mouse from the elbow jointFOREARM; resting the forearm on the work surface and moving the
mouse from the shoulder and SHOULDER; moving the mouse from the shoulder joint with the arm
unsupported
R. Wells, I.H. Lee, and S. Bao, 1996 INVESTIGATIONS OF THE OPTIMAL UPPER LIMB SUPPORT CONDITIONS FOR MOUSE USE, in: Proceeding of Human Factors Association of Canada
Department of Kinesiology,University of Waterloo
QuestionsQuestions
What changes with different support conditionsWhich is optimal?What are appropriate outcome (dependant) measures?
Answers to these questions will inform recommendations on the best practice for mouse use
Department of Kinesiology,University of Waterloo
Dependent MeasuresDependent Measures
Musculoskeletal strainElectromyography of 8 muscles of the arm and shoulderWrist goniometry
Speed/Accuracy Fitts’ tapping task
Pain and Discomfort
Department of Kinesiology,University of Waterloo
TasksTasks
i) Drawing task;
ii) Interactive text editing task
iii) Fitts’ tapping task
iv) Extended game playing.
Department of Kinesiology,University of Waterloo
Electromyographic SitesElectromyographic Sites
Electromyograms were collected from the right upper limb from surface electrodes overlying
1st dorsal interosseous (FDI), finger/wrist extensors (ED), extensor carpi ulnaris (ECU), flexor superficialis (FDS), pronator teres (PT), a combined flexor/extensor site (Thru)upper trapezius (Trap) infraspinatus (Inf).
Department of Kinesiology,University of Waterloo
Normalization of the EMG Normalization of the EMG
Against maximal efforts (MVIC), fixed effort contractions and µVolts.
Only EMG, quantified by the 10th percentile APDF values for the normalization to maximum efforts (%MVIC) will be reported here.
Department of Kinesiology,University of Waterloo
Wrist Posture MeasurementWrist Posture Measurement
recorded using flexible wrist goniometers (Penny and Giles) flexion/extension, ulnar/radial and pronation/supination
Two calibrations, statically to known angles and dynamically against a fixture instrumented to record wrist postures were made.
EMG and wrist posture were recorded for 3 minutes of continuous task performance.
Department of Kinesiology,University of Waterloo
Static EMG vs Support Static EMG vs Support Condition for Eight MusclesCondition for Eight Muscles
FDI FDS ED ECU PT Thru Trap Inf
0
1
2
3
4
5Elbow
Forearm
Shoulder (None)
Wrist
Muscle
* *
*
*
*
Department of Kinesiology,University of Waterloo
DiscomfortDiscomfort
After 3 Hours Mouse Use:
Support
N=5
Department of Kinesiology,University of Waterloo
Discomfort and Mouse UseDiscomfort and Mouse Use
After 3 Hours Mouse Use:
Shoulder Support
N=5
Department of Kinesiology,University of Waterloo
Discomfort and Mouse UseDiscomfort and Mouse Use
After 3 Hours Mouse Use:
Wrist Support
N=5
Department of Kinesiology,University of Waterloo
Discomfort and Mouse UseDiscomfort and Mouse Use
After 3 Hours Mouse Use:
Elbow Support
N=5
Department of Kinesiology,University of Waterloo
Discomfort and Mouse UseDiscomfort and Mouse Use
After 3 Hours Mouse Use:
Forearm Support
N=5
Department of Kinesiology,University of Waterloo
FindingsFindings
Based upon the above investigation the following findings are suggested:
1)The elbow support condition appeared to minimize the static load on the shoulder muscles sampled (trapezius and infraspinatus) and the forearm muscles
2)The shoulder support condition appeared to require the highest muscle activity in the shoulder muscles
3)The wrist support condition appeared to require the highest muscle activity in the muscles of the arm sampled
top related