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  • Author: Jeffrey P. Broker x
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Jeffrey P. Broker and Robert J. Gregor

In light of substantial interest in the measurement of rider-induced loads, a new bicycle pedal instrumentation system is presented. The system employs dual piezoelectric transducers and permits the measurement of three components of a uniaxial load, moments about the pedal’s vertical axis, and the point of application of the applied load. Force and moment patterns derived from pedal output agree with previously reported data. Unique to this design, however, is the determination of center of pressure—and these data indicate that the applied load location varies during the pedaling cycle, with a significant effect on the calculated pedal moment.

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

Pedal kinetics, including the applied moment (Mz) about an axis orthogonal to the pedal surface and passing through the center of pressure, were measured across three shoe/pedal interface systems (toe-clip and strap, clipless fixed, clipless float) and three workrates (150, 250, 350 W) during steady-state cycling using specially developed multicompatible force pedals. The applied moment (Mz) at the pedal is an important contributor to the corresponding axial moment realized at the knee and has implications for studying overuse injury mechanics and prevention of cycling-related knee pain. Data were collected from 27 knee pain free (KPF) cyclists and 7 cyclists with cycling-related knee pain. The largest applied moments (Mz) were observed when clipless fixed pedals were employed, while clipless float pedals significantly attenuated the applied moment. Cyclists with chronic knee pain exhibited Mz patterns markedly different from the KPF group, supporting the theory that relatively high moments, particularly internally applied moments during the power phase, may be related to knee loads and subsequent overuse injury. Our general conclusion is that clipless pedal float designs quantifiably reduce applied moments at the shoe/pedal interface without compromising power transmitted to the bike.

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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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Raoul F. Reiser II, Michael L. Peterson and Jeffrey P. Broker

While the recumbent cycling position has become common for high-performance human-powered vehicles, questions still remain as to the influence of familiarity on recumbent cycling, the optimal riding position, and how recumbent cycling positions compare to the standard cycling position (SCP). Eight recumbent-familiar cyclists and 10 recreational control cyclists were compared using the 30-s Wingate test in 5 recumbent positions as well as the SCP. For the recumbent positions, hip position was maintained 15° below the bottom bracket while the backrest was altered to investigate body configuration angle (BCA: the angle between the bottom bracket, hip, and a marker at mid-torso) changes from 100° to 140° in 10° increments. Between-groups analysis found that only 4 of the 126 analyzed parameters differed significantly, with all trends in the same direction. Therefore both groups were combined for further analysis. Whole-group peak power (14.6 W/kg body mass) and average power (9.9 and 9.8 W/kg body mass, respectively) were greatest in the 130° and 140° BCA positions, with power dropping off as BCA decreased through 100° (peak = 12.4 W/kg body mass; avg. = 9.0 W/kg body mass). Power output in the SCP (peak = 14.6 W/kg body mass; avg. = 9.7 W/kg body mass) was similar to that produced in the 130° and 140° recumbent BCA. Average hip and ankle angles increased (became more extended/ plantar-flexed), 36° and 10°, respectively, with recumbent BCA, while knee angles remained constant. The lower extremity kinematics of the 130° and 140° BCA were most similar to those of the SCP. However, SCP hip and knee joints were slightly extended and the ankle joint was slightly plantar-flexed compared to these two recumbent positions, even though the BCA of the SCP was not significantly different. These findings suggest: (a) the amount of recumbent familiarity in this study did not produce changes in power output or kinematics; (b) BCA is a major determinant of power output; and (c) recumbent-position anaerobic power output matches that of the SCP when BCA is maintained, even though lower extremity kinematics may be altered.

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Jeffrey P. Broker, Robert J. Gregor and Richard A. Schmidt

This study evaluated the retention of a cycling kinetic pattern using two different feedback schedules and evaluated the potential for feedback dependency in a continuous-task learning environment. Eighteen inexperienced cyclists rode a racing bicycle mounted to a fixed-fork Velodyne Trainer, with pedal forces monitored by dual piezoelectric transducers. Subjects received right-pedal shear force feedback and a criterion pattern emphasizing “effective” shear. Concurrent feedback (CFB) subjects received concurrent feedback 140 ms after the completion of every other revolution, while summary feedback (SFB) subjects received averaged feedback between trials. All subjects performed 10 retention trials without feedback 1 week later. Both groups improved significantly during practice, and performance decay in retention was negligible. Group differences during all phases were not significant. High CFB group proficiency in retention indicated that the detrimental aspects of frequent feedback were not significant. High SFB proficiency in retention suggests that large changes in kinetic patterning are achievable with relatively few feedback presentations.