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Kreg G. Gruben, Lynn M. Rogers and Matthew W. Schmidt

Control of the force exerted by the foot on the ground is critical to human locomotion. During running on a treadmill and pushing against a fixed pedal, humans increased foot force in a linear manner in sagittal plane force space. However, for pushes against a moving pedal, force output was linear for some participants but slightly curved for others. A primary difference between the static and dynamic pedaling studies was that the dynamic study required participants to push with varying peak effort levels, whereas a constant peak effort level was used for the fixed pedal pushes. The present study evaluated the possibility that force direction varied with level of effort. Seated humans pushed against a fixed pedal to a series of force magnitude targets. The force direction varied systematically with effort level consistent with the force path curvature observed for dynamic pedaling.

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Foot Pedals

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Brice T. Cleland and Sheila Schindler-Ivens

lower limb movement. We used functional magnetic resonance imaging (fMRI) to examine brain activation during pedaling in people with and without stroke ( Promjunyakul, Schmit, & Schindler-Ivens, 2015 ). People with stroke displayed reduced pedaling-related brain activation volume compared with age

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James Wright, Thomas Walker, Scott Burnet and Simon A. Jobson

recently pedal-based systems have not provided the same measure of reliability when compared with more traditional crank- or hub-based systems, with Sparks et al 6 suggesting that the Look Kéo power pedals were not as reliable as the SRM Powermeter during an incremental testing protocol. Recently, the

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Jeffrey B. Wheeler, Robert J. Gregor and Jeffrey P. Broker

In response to the popularity of clipless bicycle pedals with float designs, an instrumented force pedal system with multicompatibility for different shoe/pedal interfaces is presented. A dual piezoelectric element pedal has been modified for use with popular clipless pedal interfaces. The dual transducer arrangement permits measurement of three components of uniaxial load, location of the applied load, and calculation of the moment Mz about an axis through the position of the applied load and orthogonal to the pedal surface. Quantification of lower extremity kinetics using float feature pedals and the investigation of the pathomechanics of lower extremity cycling overuse injuries, especially knee injuries, is warranted. Qualitative descriptions of lower extremity pathomechanics related to overuse injuries have suggested that foot constraint may induce undesirable knee kinematics and kinetics. The instrumented force pedal system described here permits a comparison between pedal kinematics and kinetics of popular shoe/pedal interfaces with varying degrees of float allowance.

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Graham E. Caldwell, Li Li, Steve D. McCole and James M. Hagberg

Alterations in kinetic patterns of pedal force and crank torque due to changes in surface grade (level vs. 8% uphill) and posture (seated vs. standing) were investigated during cycling on a computerized ergometer. Kinematic data from a planar cine analysis and force data from a pedal instrumented with piezoelectric crystals were recorded from multiple trials of 8 elite cyclists. These measures were used to calculate pedal force, pedal orientation, and crank torque profiles as a function of crank angle in three conditions: seated level, seated uphill, and standing uphill. The change in surface grade from level to 8% uphill resulted in a shift in pedal angle (toe up) and a moderately higher peak crank torque, due at least in part to a reduction in the cycling cadence. However, the overall patterns of pedal and crank kinetics were similar in the two seated conditions. In contrast, the alteration in posture from sitting to standing on the hill permitted the subjects to produce different patterns of pedal and crank kinetics, characterized by significantly higher peak pedal force and crank torque that occurred much later in the downstroke. These kinetic changes were associated with modified pedal orientation (toe down) throughout the crank cycle. Further, the kinetic changes were linked to altered nonmuscular (gravitational and inertial) contributions to the applied pedal force, caused by the removal of the saddle as a base of support.

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Håvard Lorås, Gertjan Ettema and Stig Leirdal

Changes in pedaling rate during cycling have been found to alter the pedal forces. Especially, the force effectiveness is reduced when pedaling rate is elevated. However, previous findings related to the muscular force component indicate strong preferences for certain force directions. Furthermore, inertial forces (due to limb inertia) generated at the pedal increase with elevated pedaling rate. It is not known how pedaling rate alters the inertia component and subsequently force effectiveness. With this in mind, we studied the effect of pedal rate on the direction of the muscle component, quantified with force effectiveness. Cycle kinetics were recorded for ten male competitive cyclists at five cadences (60–100 rpm) during unloaded cycling (to measure inertia) and at a submaximal load (~260 W). The force effectiveness decreased as a response to increased pedaling rate, but subtracting inertia eliminated this effect. This indicates consistent direction of the muscle component of the foot force.

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Harsh H. Buddhadev, Daniel L. Crisafulli, David N. Suprak and Jun G. San Juan

range of motion. 10 To our knowledge, however, no research has examined pedaling mechanics bilaterally in individuals with knee OA during cycling under submaximal conditions, despite the known therapeutic benefits of cycling. During cycling, power output at the crank is representative of net muscular

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Birgit Larsen, Michael Voigt and Michael J. Grey

The influence of pedaling frequency and crank load on the sensitivity of the soleus short latency stretch reflex (SLR) was examined in nine healthy subjects during pedaling by the use of a custom-built robotic actuator. The SLR decreased successively in downstroke when pedaling frequency increased from 20 to 40 and 60 revolutions per minute at a constant crank load (p = .005). The SLR was unchanged at crank load increases of 2.6 or 5.1 Nm at a constant pedaling frequency (p > .05). Accordingly, it was shown that increased muscle activation level as a consequence of added crank load and increased movement speed does not increase the sensitivity of the soleus SLR.

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Cheryl D. Pierson-Carey, David A. Brown and Christine A. Dairaghi

The purpose of this study was to determine the effects of limiting ankle motion on pedal forces. Sixteen adults pedaled an instrumented ergometer against constant cadence and frictional load while wearing hinged braces. Ankle motion was limited under four randomly assigned conditions: both braces unlocked (UL), only the preferred leg (PL) brace locked, only the nonpreferred leg (NPL) brace locked, and braces on both legs (BL) locked. Measurements of pedal force, crank, and pedal angles were sampled at 200/s for 20 s. With both braces locked, resultant force mean magnitude decreased during the downstroke, due to reduced radial crank force. Asymmetry between PL and NPL decreased during the power phase when only PL was braced but increased when only NPL was braced. It was concluded that constrained ankle motion, as may occur with ankle injury or hemiplegia, reduces the ability to transmit power during the downstroke while enhancing ability during the upstroke.