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Presidential Closing Remarks 12: 05 PM – 12: 15 PM: Immediately Following President's Lectures ROOM: Ballroom 2/3 and Ballroom 1: F-54 Free Communication/Slide – Equipment Design and Performance: FRIDAY, JUNE 2, 2006 3: 15 PM – 5: 15 PM ROOM: 302

Whole Body Vibrations on the Low Back Using a Suspension Versus Non-Suspension Seat Post During Off-Road Cycling


3:30 PM – 3:45 PM

Stanley, Laura M.; Marley, Robert J.

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Medicine & Science in Sports & Exercise: May 2006 - Volume 38 - Issue 5 - p S106
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Mountain bikes were introduced nearly two decades ago and have since become the number-one type of bicycle sold in PMerica. Nearly every major bicycle manufacturer now offers many types of suspensions systems. The rationale behind a suspension system is that it provides: (a) increased comfort levels, (b) decreased fatigue, and (c) fewer injuries. However, many of these claims are purely anecdotal and are not based on scientific evidence. Accordingly, more quantitative measures need to be taken to assess the effect of bicycle shock absorption systems on skeletal loading, muscle fatigue, and potential injury.

PURPOSE: The objective of this study was to compare the effects of a suspension and a non-suspension seat post on whole body vibration energy and muscle activity in the lumbar and abdominal muscles during off-road cycling in recreational cyclists.

METHODS: A randomized block ANOVA with repeated measures was used to document the effects of seat condition over one hour riding in off-road conditions. Acceleration of the seat and EMG activity of abdominal and low back muscles were recorded.

RESULTS: The findings of this study indicate that there were no significant (p >0.05) differences in muscle activity (peak PMplitude, median frequency, and 95% of frequencies) between the seat post treatments. The suspension seat post did not significantly reduce total vibration energy (p = 0.816) or the total vibration energy (p = 0.412) during impact with the simulated obstacles, though the suspension seat post significantly (p = 0.02) reduced peak accelerations by up to 27%. Furthermore, an early indication of muscular fatigue was observed in the low back and abdominal muscle regions during the riding sessions based upon EMG frequency analysis. A 10% decrease in median frequency was observed during both riding sessions.

CONCLUSIONS: This study suggests that the suspension seat post's ability to reduce peak accelerations will prolong the time at which the onset of muscular fatigue occurs. It is believed that muscle fatigue of the core muscles may contribute to low back pain. Any delay in the reduction in muscle power might result in less or no low back pain. Additionally, reducing peak accelerations will place less strain on the spinal structures with the anticipation of reducing any cervical, dorsal, or lumbar back pain or injury. As an off-road cyclist, the suspension seat post would be health beneficial because of its characteristics in reducing peak accelerations.

© 2006 American College of Sports Medicine