An EMG-driven model to evaluate quadriceps strengthening after an isokinetic training

This paper uses a Hill-type EMG-Driven model to estimate isometric quadriceps forces of 4 males subjects after a strength training period in an isokinetic device (Cybex-Norm), aiming for muscle hypertrophy. Before (PRE) and after (POS) training, quadriceps PCSAs were estimated from ultrasound measurements. Each individual followed a protocol of 10 s submaximal (20% and 60%MVC) knee extension isometric contractions. Knee torque and surface EMG from three superficial quadriceps components were synchronously collected. EMG signal from vastus intermedius was estimated from other muscles. After training, the subjects presented an increase of 14.3 ± 5.1% of the maximum isometric torque, while the gain of muscle volume was 6.0 ± 3.0%. RMS error between EMG-driven and dynamometer joint torques, for the best estimation condition, were: 20%MVC PRE= 10.8 ± 3.8%, POS = 11,0 ± 4.9%; 60%MVC PRE = 12.1 ± 3.2%, POS = 8.3 ± 2.5%. These results are analyzed under the viewpoint of modeling and experimental reliability.