Figure 1. Joint markers in the Stairmaster (left) and the stair climbing (right) tasks. Joint markers were placed over the shoulder, hip, knee and ankle.
The subject used in this motion analysis was a 22 year old female wearing tight black clothing and white tennis shoes. She weighed 489.5 N and was 1.575 m tall. Joint markers were placed on the subject's shoulder (acromion process), hip (greater trochanter), knee (lateral epicondyle), and ankle (lateral malleolus). The subject had experience on the Stairmaster, but previous experience or skill were not required for the two movements.
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Figure 1. Joint markers in the Stairmaster (left) and the stair climbing (right) tasks. Joint markers were placed over the shoulder, hip, knee and ankle. | |
A JVC VHS video camera with a speed set at 30 frames/second was used to videotape both motions. The Stairmaster movement was recorded in the Central Campus Recreation Building at the University of Michigan. The stair climbing movement was recorded in the Chemistry building also located at the University of Michigan. The video camera was placed approximately at a distance of 3.5 m away from the subject, perpendicular to the subject's sagittal plane. No special lighting was required. The subject was told to perform the motions continuously for 5 minutes, looking straight ahead. The criteria used to select trials for analysis was one complete smooth cycle from left leg extension to left leg extension. In addition, frames could not contain other individuals walking by.
The videotaped images were digitized at 30 frames/s using FusionRecorder on Macintosh computers in the New Media Center at the University of Michigan. The digital video files were trimmed using MoviePlayer so that the data files contained only the frames between the start and end of the movements. A custom utility (QT->PICT) was used to convert the Quicktime movie files into a series of individual frame files in PICT format for use with the Motion Plus software. Four joint markers placed over the shoulder, hip, knee, and ankle were digitized using Motion Capture. Joint marker coordinate data were exported in spreadsheet format to Excel for biomechanical analysis using Motion Analyse.