Fig. 3
a Quadriceps maximal voluntary torque (QMVC), b quadriceps maximal peak twitch (QPt), c voluntary activation estimated with motor cortex transcranial magnetic stimulation during maximal voluntary contractions [VAcortical (%)], and d voluntary activation estimated with twitch interpolation during maximal voluntary contractions [VAperipheral (%)], in healthy controls, patients with COPD and preserved muscle strength (COPDNoMW), and patients with COPD and muscle weakness (COPDMW). *, **, ***: p < 0.05, p < 0.01 and p < 0.001 respectively. Vertical bars represent SE