kevin levi-goerlich bam journal club 9/26
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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. - PowerPoint PPT PresentationTRANSCRIPT
Kevin Levi-GoerlichBAM Journal Club 9/26
Introduction
CyclingPush down on pedal in order to go forwardMaximal speed for minimal energy expenditure
Pedaling mechanicsGoal is to maximize the amount of power generated
during each strokeEmphasis on a smooth pedal stroke
IntroductionChainrings
- Circular
-Non-circular
Why?
Introduction
IntroductionIs a non-circular chain-ring more efficient?
If so, what shape?
What offset?
MethodsForward dynamic muscle model simulation
Model9 segments10 muscle groups
Chain Ring OptimizationCirclesEllipsesRounded SquaresOrientation
MethodsAnalysis
Model was run at cadence of 60, 90, and 120rpm4 complete cycles were performed
Data was extracted from the last cycleMuscular work was compared in each region to the
circular control model.
Results
Discussion
Elliptical Chain Rings yielded the greatest improvement in powerEccentricity of 1.29 yielded a 3% improvement at
90rpm when compared to circular simulationAngular Velocity decreases
Takes advantage of force-length-velocity properties of muscles
Discussion
DiscussionInjury potential
Most cycling overuse injuries are due to knee joint forcesThe increased duration in the “power phase” may
increase joint torques and increase knee injury potential. 9.4%increase
However45% 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.
DiscussionLimitations
Constraints from the Hill—Muscle modelForce depressionMuscle activation-deactivation changes
Drive train characteristicsNegligible
Fixed hip positionUsed known circular chain ring positionHip movement is possible, but unlikely.
DiscussionApplication
This study focuses on maximal force output, however the same optimized chain ring conditions could benefit submaximal cycling performance.
Questions?
ReferencesCycling 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.