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Kevin Levi-Goerlich BAM Journal Club 9/26

Kevin Levi-Goerlich BAM Journal Club 9/26. Introduction. Cycling Push down on pedal in order to go forward Maximal speed for minimal energy expenditure Pedaling mechanics Goal is to maximize the amount of power generated during each stroke Emphasis on a smooth pedal stroke. Introduction.

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Kevin Levi-Goerlich BAM Journal Club 9/26

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  1. Kevin Levi-Goerlich BAM Journal Club 9/26

  2. Introduction • Cycling • Push down on pedal in order to go forward • Maximal speed for minimal energy expenditure • Pedaling mechanics • Goal is to maximize the amount of power generated during each stroke • Emphasis on a smooth pedal stroke

  3. Introduction • Chainrings - Circular -Non-circular Why?

  4. Introduction

  5. Introduction • Is a non-circular chain-ring more efficient? • If so, what shape? • What offset?

  6. Methods • Forward dynamic muscle model simulation • Model • 9 segments • 10 muscle groups • Chain Ring Optimization • Circles • Ellipses • Rounded Squares • Orientation

  7. Methods • Analysis • Model was run at cadence of 60, 90, and 120rpm • 4 complete cycles were performed • Data was extracted from the last cycle • Muscular work was compared in each region to the circular control model.

  8. Results

  9. Discussion • Elliptical Chain Rings yielded the greatest improvement in power • Eccentricity of 1.29 yielded a 3% improvement at 90rpm when compared to circular simulation • Angular Velocity decreases • Takes advantage of force-length-velocity properties of muscles

  10. Discussion

  11. Discussion Injury potential • Most cycling overuse injuries are due to knee joint forces • The increased duration in the “power phase” may increase joint torques and increase knee injury potential. • 9.4%increase • However • 45% reduction in the shear and normal force impulses in the patellofemoral joint and shear forces in the tibiofemoral joint when using optimal chaing ring. • Reduced injury potential at the most vulnerable part of the pedal stroke.

  12. Discussion Limitations • Constraints from the Hill—Muscle model • Force depression • Muscle activation-deactivation changes • Drive train characteristics • Negligible • Fixed hip position • Used known circular chain ring position • Hip movement is possible, but unlikely.

  13. Discussion Application • This study focuses on maximal force output, however the same optimized chain ring conditions could benefit submaximal cycling performance.

  14. Questions?

  15. References • Cycling Muscle Usage. (n.d.). Retrieved from http://www.bikejames.com/wp-content/uploads/2012/05/ 20090505_032518_CyclingMusclesC.gif • Rankin, J. W., & Neptune, R. R. (2008). A theoretical analysis of an optimal chainring shape to maximize crank power during isokinetic pedaling. Journal of Biomechanics, 41(28), 1494-1502.

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