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Horscroft, R D.1; Davidson, C J.1; McDaniel, J1; Wagner, B M.1; Martin, J C. FACSM1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S16
A-15G Free Communication/Thematic Poster Cycling

1University of Utah, Salt Lake City, Utah

Previous investigators have reported that saddle height alters metabolic efficiency during sub-maximal cycling. We hypothesized that changes in metabolic efficiency result from alterations in the proportion of total power produced at the ankle, knee, and hip.

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To determine if altered saddle height elicits changes in the proportion of crank power produced at the ankle, knee, and hip.

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Four well-trained male cyclists cycled with their accustomed saddle height and with that height reduced by 6 cm. Subjects maintained a pedaling rate of 100 rpm and a workload of 300 watts for 1 minute. Pedal forces, and pedal and crank position were sampled at 200 Hz. Two-dimensional leg kinematics were computed using the geometric relationships of the 5-bar linkage, and the hip was assumed to remain fixed. Net joint moments were determined using inverse dynamic techniques. Joint powers were calculated as the product of net joint moments and joint angular velocities and were averaged over 7 complete crank revolutions. The proportions of total crank power produced at each joint were determined. The absolute value of relative changes at the hip and knee were also determined.

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Mean relative joint powers at the ankle, knee, and hip did not differ when cycling with the accustomed saddle height (14.4 ± 3.5, 42.4 ± 7.2, and 43.2 ± 5.9% respectively mean±SE) compared with the reduced saddle height (13.2 ± 2.5, 39.0 ± 5.1, and 47.8 ± 3.4%). The absolute values of the changes at the ankle knee and hip were 1.3 ± 0.6, 6.3 ± 2.0, 6.1 ± 2.7% respectively, and the difference at the knee was significantly different than zero (P < .05).

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Cycling with a reduced saddle height did not elicit significant changes in joint power distribution. However, the absolute value of shifts in power distribution at the knee joint was found to be significant. Based on these data we conclude that alterations in saddle height do not elicit consistent shifts in power production from one joint to another but do elicit individual shifts.

©2003The American College of Sports Medicine