multiple leg muscles with proper timing and intensity to produce pedal forces in a direction that produces appropriate crank torque, even though that direction is constantly changing with respect to gravitational acceleration. For example, Kautz and Hull ( 1993 ) found that gravity itself produces pedal
Sangsoo Park, Richard Van Emmerik, and Graham E. Caldwell
Fábio J. Lanferdini, Rodrigo R. Bini, Pedro Figueiredo, Fernando Diefenthaeler, Carlos B. Mota, Anton Arndt, and Marco A. Vaz
To employ cluster analysis to assess if cyclists would opt for different strategies in terms of neuromuscular patterns when pedaling at the power output of their second ventilatory threshold (POVT2) compared with cycling at their maximal power output (POMAX).
Twenty athletes performed an incremental cycling test to determine their power output (POMAX and POVT2; first session), and pedal forces, muscle activation, muscle–tendon unit length, and vastus lateralis architecture (fascicle length, pennation angle, and muscle thickness) were recorded (second session) in POMAX and POVT2. Athletes were assigned to 2 clusters based on the behavior of outcome variables at POVT2 and POMAX using cluster analysis.
Clusters 1 (n = 14) and 2 (n = 6) showed similar power output and oxygen uptake. Cluster 1 presented larger increases in pedal force and knee power than cluster 2, without differences for the index of effectiveness. Cluster 1 presented less variation in knee angle, muscle–tendon unit length, pennation angle, and tendon length than cluster 2. However, clusters 1 and 2 showed similar muscle thickness, fascicle length, and muscle activation. When cycling at POVT2 vs POMAX, cyclists could opt for keeping a constant knee power and pedal-force production, associated with an increase in tendon excursion and a constant fascicle length.
Increases in power output lead to greater variations in knee angle, muscle–tendon unit length, tendon length, and pennation angle of vastus lateralis for a similar knee-extensor activation and smaller pedal-force changes in cyclists from cluster 2 than in cluster 1.
Rodrigo R. Bini and Patria A. Hume
The accuracy of commercial instrumented crank systems for symmetry assessment in cycling has not been fully explored. Therefore, the authors’ aims were to compare peak crank torque between a commercial instrumented crank system and instrumented pedals and to assess the effect of power output on bilateral asymmetries during cycling. Ten competitive cyclists performed an incremental cycling test to exhaustion. Forces and pedal angles were recorded using right and left instrumented pedals synchronized with crank-torque measurements using an instrumented crank system. Differences in right (dominant) and left (nondominant) peak torque and asymmetry index were assessed using effect sizes. In the 100- to 250-W power-output range, the instrumented pedal system recorded larger peak torque (dominant 55–122%, nondominant 23–99%) than the instrumented crank system. There was an increase in differences between dominant and nondominant crank torque as power output increased using the instrumented crank system (7% to 33%) and the instrumented pedals (9% to 66%). Lower-limb asymmetries in peak torque increased at higher power-output levels in favor of the dominant leg. Limitations in design of the instrumented crank system may preclude the use of this system to assess peak crank-torque symmetry.
Chee-Hoi Leong, Steven J. Elmer, and James C. Martin
., Amherst, NY, USA). These data were highly linear ( r 2 > .999). Two-dimensional kinematic and kinetic data were obtained using the methods originally described by Martin and colleagues 21 and utilized in previous investigations from our laboratory. 13 , 22 , 23 Briefly, pedal forces, pedal and crank
Chee-Hoi Leong, Steven J. Elmer, and James C. Martin
reaction forces and net joint torques at the ankle, knee, and hip were determined using inverse dynamics techniques. 27 Normal and tangential pedal forces were resolved into vertical ( z -axis) and horizontal ( y -axis) components using pedal and crank position data. Pedal power was calculated as the dot
Ewald M. Hennig and David J. Sanderson
Foot function and possible mechanisms for the etiology of frequently observed forefoot complaints in bicycling were studied. Pedal forces and in-shoe pressure distributions were measured with 29 subjects, who rode on a stationary bicycle with a cadence of 80 rpm at 100, 200, 300, and 400 W. The influence of footwear on foot loading was also investigated by comparing running and bicycling shoes at 400 W. The first metatarsal head and the hallux were identified as the major force-contributing structures of the foot. High pressures under the toes, midfoot, and under the heel showed that all foot areas contribute substantially to the generation of pedal forces. For increasing power outputs, higher peak pressures and relative loads under the medial forefoot were identified. These may cause pressure-related forefoot complaints and accompany increased foot pronation. As compared to the running shoe, the stiff bicycling shoe demonstrated a more evenly distributed load across the whole foot and showed a significantly increased index of effectiveness.
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.
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.
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.
Karen L. Perell, Robert J. Gregor, and A.M. Erika Scremin
The purpose of this sludy was to compare individual pedal reaclion force components following bicycle training with and without effective force feedback in subjects with unilateral cerebrovascular accident (CVA). Eight ambulatory subjects with CVA were studied on a recumbent bicycle equipped with custom-built pedals, which measure normal and tangential components of the load applied to the pedal surface. Comparisons of normal and tangential pedal reaction forces were made following 1 month of bicycle training (3 times/week for 4 weeks) during retention tests performed without feedback. The ratios of involved to contralateral (I/C ratios) force parameters were used to assess symmetry. Subjects were randomly assigned to 2 groups: (a) a feedback group that received visual/verbal feedback regarding effective force patterns, bilaterally, after each trial; and (b) a no-feedback group dial received no feedback. Two critical results were found: (a) tangential pedal forces were significantly more posteriorly directed bilaterally following training across all subjects, but the change was greater for the no-feedback group relative to the feedback group, and (b) effective force feedback training did not demonstrate improvements in the I/C ratios above that of the control group. A more posteriorly applied tangential pedal force may represent increased dorsiflexion and may suggest that bicycle training facilitated ankle control. The cyclical nature of cycling, however, may allow for natural patterns to develop without feedback or may require less frequent use of feedback based on retention test performance.