DORSIFLEXOR AND PLANTARFLEXOR TORQUE-ANGLE AND TORQUE-VELOCITY RELATIONSHIPS OF CLASSICAL BALLET DANCERS AND VOLLEYBALL PLAYERS

Abstract

The purpose of this study was to compare the torque-angle and torque-velocity relationships, and the electromyographic (EMG) activity of the plantar- and dorsiflexor muscle groups of classical ballet dancers (n=14) and volleyball players (n=22). Peak torques of the ankle plantar- and dorsiflexor muscles were evaluated for maximal voluntary isometric contractions performed at seven different ankle angles (-10°, 0°, 10°, 20°, 30°, 40°, 50°) and for maximal effort, concentric, voluntary contractions performed at angular velocities of 0°/s, 60°/s, 120°/s, 180°/s, 240°/s, 300°/s, 360°/s and 420°/s. Bipolar surface EMG signals were obtained from gastrocnemius medialis, soleus and tibialis anterior muscles, and ankle range of motion was measured with a goniometer. The range of motion for dorsiflexion was the same for both groups, while ballet dancers had a greater range for plantarflexion than volleyball players. For the plantarflexor muscles, the torque-angle relationship was shifted to the left for the ballet dancers compared to the volleyball players, while for the dorsiflexor muscles it was shifted to the right for short dorsiflexor lengths. The normalized torques at all speeds of plantar- and dorsiflexion were greater for the ballet dancers than the volleyball players. The gastrocnemius medialis and soleus EMGs remained nearly constant across all angles for the ballet dancers, but decreased with decreasing muscle length in the volleyball players. The tibialis anterior EMGs increased with decreasing ankle angles in both groups. The normalized dorsiflexor EMGs were the same for both groups across all speeds, while the EMGs for soleus and gastrocnemius were significantly greater for the ballet dancers than the volleyball players. These results support the idea that systematic physical activity changes the in vivo torque-angle and torque-velocity relationships in accordance with functional demands. The greater relative torques for the ballet dancers than volleyball players are likely caused by the increased activation of the plantarflexors and an increased fiber length for the dorsiflexors.