Program > Saturday > 11:15 > Session 10. Work-related musculoskeletal disorders (2/2)

Paper: Transmission of acceleration from vibrating exercise platforms to the lumbar spine and head
Author(s) and Affiliation(s):
Robert Caryn BA, Joint Biomechanics Laboratory The University of Western Ontario
J.P. Dickey PhD, Joint Biomechanics Laboratory The University of Western Ontario
Alan Salmoni PhD, The University of Western Ontario
Peter Lemon PhD, The University of Western Ontario
Tom J. Hazell MSc, The University of Western Ontario
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Session : 10. Work-related musculoskeletal disorders (2/2)
Day/Time: Saturday at 11:15
Room: Ballroom, 2nd Floor
Objectives:

Whole Body Vibration platforms have become a popular modality in the fitness and rehabilitation industry. Whole body vibration has also been identified as a cause of injury in occupational settings [2]. The goal of this study was to quantify the accelerations experienced at the axial skeleton during standing vibration. This study investigated which knee angles effectively dampened vibration to the upper body.

Methods:

Healthy male and female subjects completed whole body vibration trials on a vibrating platform (WAVE) that generated vertical vibrations at 2 and 4 mm amplitudes between frequency ranges of 20 to 50Hz. A twin axis electrogoniometer (Biometrics SG 150) was used to monitor knee flexion during static squat and dynamic squat trials. A reference measurement made at the platform was compared to accelerations measured at the greater trochanter, 5th lumbar vertebrae, and skull. All accelerations were measured with triaxial accelerometers (Biometrics ACL 300/PCB Piezotronics). A published transfer function was used to calculate accelerations at the bone from the accelerations recorded at the skin [1]. A transfer function was used to determine changes in both magnitude and phase of the input mechanical signal at each measurement point.

Results:

Peak vertical accelerations of the platform ranged from 1 to 6.50 g. RMS accelerations experienced at the spine (0.445 g) and head (1.01 g) were greatest when the knees were close to full extension, resulting in the greatest transmission of mechanical energy.

Conclusions:

The recorded accelerations illustrate that the body is a nonlinear system. Large amounts of mechanical energy can be passed through the axial skeleton during whole body vibration; keeping the legs near full extension should be avoided. More research is needed to explore the long-term health effects that may be caused by whole body vibration through the feet.

References:

[1] Kitazaki, S., and Griffin, M.J., “A Data Correction Method for Surface Measurement of Vibration on the Human Body,” J. of Biomechanics, Vol. 28, No. 7, pp. 885-890, 1995
[2] Randall, J.M., Matthews, R.T., and Stiles, M.A., “Resonant Frequencies of Standing Humans,” Ergonomics, Vol. 40, No. 9, 879-886, 1997.