Joint Power Distribution At 60, 90, And 120 Rpm During Seated Maximal Cycling

Abstract

Power is delivered to cycling cranks by muscles that span the ankle, knee, and hip, and by muscles in the upper body. The relative contribution of each of those power sources has been reported for submaximal cycling, but not for maximal cycling. Joint power distribution during submaximal cycling likely represents an optimal control strategy, whereas maximal cycling likely represents maximal power production at each joint and may be more sensitive to pedaling rate. PURPOSE The purpose of this investigation was to compare the relative contribution of power produced at the ankle, knee, and hip, and transferred across the hip, to maximal cycling power at pedaling rates of 60, 90, and 120rpm. METHODS Seven trained cyclists [(Mean±SD); Age=29±9 yrs, Height=175±.7cm, Mass=73±8 kg] cycled maximally on an isokinetic cycle ergometer at 60, 90 and 120 rpm. Pedal forces, and pedal and crank position were sampled at 240 Hz for 5 seconds. Hip position was determined with a 2-camera motion capture system and two-dimensional leg kinematics were geometrically determined. Net joint moments and joint reaction forces were determined using inverse dynamic techniques. Joint powers for the ankle, knee, and hip were calculated as the product of net joint moment and joint angular velocity and power delivered across the hip joint was calculated as the dot product of joint reaction force and joint linear velocity and the proportions of total crank power produced at each joint were determined. Relative joint powers were analyzed with repeated measures ANOVA followed by LSD post hoc contrasts. RESULTS For each pedaling rate, the knee generated the greatest portion of crank power (50±3, 51±4, and 49±6% for 60, 90, and 120rpm respectively), followed by the hip (24±8, 25±8, and 31±7% respectively) and power delivered by the ankle joint (15±3, 12±3, and 9±2% respectively) was similar to power delivered across the hip joint (10±3, 10±3, 9±2% repectively). The relative contributions of power produced at the knee and transferred across the hip did not differ across pedaling rates. Ankle power and hip joint power at 60 rpm differed from those at 120rpm. CONCLUSIONS These data demonstrated that relative contributions of joint power to maximal cycling power were altered with pedaling rate and that the hip joint was relatively greater at faster pedaling rates whereas the ankle was relatively greater at slower rates. These data may have important implications for training of cyclists and for physical therapy of patients.