Raymond Lee | PubMed Health

PubMed2002

An ergonomic evaluation comparing desktop, notebook, and subnotebook computers.

OBJECTIVE: To evaluate and compare the postures and movements of the cervical and upper thoracic spine, the typing performance, and workstation ergonomic factors when using a desktop, notebook, and subnotebook computers. DESIGN: Repeated-measures design. SETTING: A motion analysis laboratory with an electromagnetic tracking device. PARTICIPANTS: A convenience sample of 21 university students between ages 20 and 24 years with no history of neck or shoulder discomfort. INTERVENTION: Each subject performed a standardized typing task by using each of the 3 computers. MAIN OUTCOME MEASURES: Measurements during the typing task were taken at set intervals. RESULTS: Cervical and thoracic spines adopted a more flexed posture in using the smaller-sized computers. There were significantly greater neck movements in using desktop computers when compared with the notebook and subnotebook computers. The viewing distances adopted by the subjects decreased as the computer size decreased. Typing performance and subjective rating of difficulty in using the keyboards were also significantly different among the 3 types of computers. CONCLUSIONS: Computer users need to consider the posture of the spine and potential risk of developing musculoskeletal discomfort in choosing computers.

Adult↗

PubMed1997

An in vivo study of the intervertebral movements produced by posteroanterior mobilization.

OBJECTIVE: To measure the intervertebral movements of the lumbosacral spine when it was subjected to posteroanterior mobilization. DESIGN: An in vivo radiographic study. BACKGROUND: Posteroanterior mobilization is frequently employed in the examination and treatment of low back pain, but its mechanical and therapeutic effects are uncertain. METHODS: Lateral radiographs were taken of 12 healthy male subjects who were in prone lying. This was repeated while a static mobilization force of 150 N was applied vertically to their L4 spinous processes. The radiographic images of the vertebrae were traced and digitized. The sagittal rotation and translations of the motion segments, and the displacements of the spinous processes were then computed. RESULTS: Under the application of the mobilization loads, the lumbar motion segments were found to extend, whereas the L5/S1 segment tended to flex. It was also shown that the upper lumbar segments (L1/2-L3/4) translated posteriorly and the L5/S1 segment anteriorly. The L4/5 segment did not exhibit translation in a consistent direction. In addition, all the spinous processes were found to be displaced anteriorly. CONCLUSIONS: The movement pattern observed in this study strongly suggests that the spine is subjected to three-point bending under the application of mobilization loads. RELEVANCE: The intervertebral movements produced by posteroanterior mobilization were small in magnitude, and it is unlikely that the therapist can assess these movements manually with reasonable reliability. Mobilization should be interpreted as a passive test of the whole lumbar spine in three-point bending.

Journal Article↗