Maximum isokinetic ankle plantar and dorsal flexion torques in trained subjects

Isokinetic ankle plantar- and dorsal-flexion torques, IPF and IDF, respectively, were measured in twenty-five physically healthy athletes, fifteen males and ten females, with simultaneous recording of rectified, linearly enveloped surface electromyograms, and peak electromyographic tensions (PEMG). Angular delays from the start of motion to occurrence of peak torques were also registered. Manoeuvres were performed in two knee positions. For comparison of strength 30 non-athletic (untrained) controls were included. IPF, but not IDF, was greater in the trained than in the untrained subjects. Formulae for estimation of IPF at 30 degrees differ between trained and untrained subjects. Smaller gender differences in maximum strength for trained than for untrained subjects suggest that habitual rather than genetic dissimilarities cause sex differences in strength. Slope differences in the negative exponential models which characterize IPF and IDF as functions of increasing velocity of angular motion may be caused by different structural properties of ankle flexors and extensors. A lower PEMG of the m. gastrocnemius in the flexed than in the extended knee positions can explain the lower IPFs, suggesting that mechanical rather than supraspinal factors cause postural IPF differences. In contrast, greater IDF in the flexed than in the extended knee positions may indicate that neurogenic mechanisms are involved.