The functional roles of the hamstrings and quadriceps during cycling: Lombard's Paradox revisited.

The purposes of this study were to describe the functional roles of the hamstrings and quadriceps at the hip and knee during cycling as determined both by the standard kinetic (SK) classification method and by the Andrews kinematic (AK) classification method (Andrews, J. biomech Engng 107, 348-353, 1985), and to examine the effect of using these two different methods on the existence of paradoxical muscle behavior (Lombard's Paradox). The results of this study indicated that the functional roles determined by the SK and AK methods differed considerably, and these differences led to the existence of paradoxical behavior in the hamstrings and quadriceps at different regions of the crank cycle. Both classification methods led to the existence of considerable paradoxical muscle behavior, with the SK method predicting somewhat more non-paradoxical activity and somewhat less paradoxical activity than the AK method at both the hip and the knee.