Stimulation pattern and schematic view of the experimental protocol.

<p>Upper panel presents the two stimulation patterns. Lower panel presents the experimental protocol. Warm-up consisted of 10 progressive voluntary contractions until the maximal voluntary contraction (MVC). The experimental session then began with different measurements (<i>PRE measurement</i>s) including the determination of the optimal stimulation intensity for doublets, tetanic contractions and the session's pattern and tests with two MVCs and two 500 ms tetanic contractions at 20 and 80 Hz. Then, subjects underwent 30 minutes with one stimulation pattern. After the session, <i>POST measurements</i> were performed including two MVCs, doublets, two 500 ms tetanic contractions at 20 and 80 Hz.