Research Study - Ergonomic Test of the Kinesis Contoured Keyboard - 3

Results
Posture Analysis
The eleven subjects that participated in the EMG analysis were video-taped for postural analysis. The following are some observations from review of postural data;

Hand Extension:
Subjects demonstrated hand extensions one and one half times higher on the traditional keyboard (19.9 degrees) than on the Kinesis (I 2.4 degrees). Extension on the traditional keyboard was about 5 degrees greater than the maximum recommended hand extension of 15 degrees from neutral position. Extension on the Kinesis averaged three degrees less (12 degrees) than the maximum recommended position of 15 degrees.

During later sessions, subjects sat in more reclined position while using both keyboards and exhibited less hand extension.

Hand Deviation:
Average hand deviation was substantially higher on the traditional than on the Kinesis keyboard. Average hand deviations on the traditional keyboard ranged from 2 to 15 degrees greater than the recommended maximum deviation of 10 degrees; average deviation on the Kinesis was one degree less than the maximum recommendation.

EMG Analysis
Electrical activity of the muscles controlling deviation, extension and pronation was substantially higher during keying on the traditional keyboard. This trend was consistent throughout all six sessions. EMG activity of all four muscles was lower during random letter keying than during text entry with both keyboards.

Day 1 Test ................................................ Day 2 Test

After all of the six sessions had been completed, each. subject was given two questionnaires to complete. One questionnaire was required by the ISO test methodology (see Appendix P) and the other was developed by Kinesis (see Appendices C & D). Subjects were also given another questionnaire developed by Kinesis at the completion of the final day of testing (see Appendix E).

All subject input was stored on the HP PC. Keying performance was evaluated by calculating the number of words in text entry, keystrokes in random entry, and errors during each session.

Action EMG Dynamic Evaluation Software recorded eight EMG measures per second in 30- second increments for each of the six 20-minute sessions per keyboard. Of the possible 9,600 measurements (480 measures/minute x 20 minutes/session), 7,600 measurements were recorded far each session (due to the down time between each of thirty four 30-second increments). There were thus 7,600 measurements per channel for each 20-minute session, totaling 45,600 measurements per channel for the 6 sessions per day.

Postural data was calculated by measuring band and arm angle deviation from neutral postures on video images with a goniometer.

Channel 1: The EMG activity of the extensor carpi ulnaris muscle (indicating ulnar deviation) was substantially and consistently higher on the traditional keyboard than on the Kinesis (see Figure 2). There was a slight decrease in EMG activity during random letter keying for both keyboards.

EMG Data

Figure 2

Channel 2 : The EMG activity for the extensor communis digitorum muscle (indicating extension) was substantially and consistently higher on the traditional keyboard than on the Kinesis (see Figure 3). There was a decrease in EMG activity during random letter keying for both keyboards. The decrease in EMG was greater for the Kinesis keyboard, indicating lower muscle load.

EMG Data

Figure 3

Channel 3: The EMG activity for the deltoid muscle (indicating arm abduction at the elbow) was almost the same for the two keyboards (see Figure 4). The activity of this muscle was lowest of all the recorded muscle activity There was a slight decrease in EMG activity during random letter keying on both keyboards.

EMG Data

Figure 4

Channel 4: The EMG activity for the pronator radii teres (indicating arm pronation) was higher on the traditional keyboard than on the Kinesis (see Figure 5). There was an equivalent decrease in EMG activity during random letter keying for both keyboards.

EMG Data

Figure 5

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