A prototype for dynamic knee extension: construction, force characterization and electromyographic responses

BACKGROUND: In the dynamic knee extension (DKE), a metal bar is positioned parallel to the bicycle frame, replacing the pedal and allowing consecutive extensions instead of a pedaling movement. In this exercise model, the knee joint returns to its initial position passively, allowing studies about the role of anterior thigh muscles during locomotion or balance. However, the DKE ergometer is not commercially available. AIM: To describe the construction, responses, and applicability of a prototype ergometer for DKE. METHOD: In the first experiment, six participants underwent a progressive effort to volitional exhaustion. The electromyography signals of the Vastus Lateralis and Biceps Femoris were monitored. In the second experiment, the twitch interpolation technique was used to test the fatigue status of seven participants after a high-intensity exercise. RESULTS: The force signal has three phases: I: knee extension moment; II: crank draws the metal rod back; III: rapid compression of the load cell by the leg. In addition, Vastus Lateralis activation was higher than Biceps Femorisin all stages (p<0.02). The TI was sensitive to assess the peripheral characteristics of the high-intensity effort. CONCLUSION: The construction of a DKE ergometer is plausible, increasing the possibilities of research into motor behavior.