Fig. 1.

A) Constant isometric force task with the FDI muscle. Representative trial from 1 subject when exerting a constant force at 15% MVC with a visual angle of ~0.3°. Each subject was instructed to exert a force with abduction of the index finger against a force transducer and match the horizontal target line for 22 seconds. Visual feedback of the target line (red line) and exerted force (black trace) was given to the subjects from 0–8 s and 12–16 s (visual feedback condition), whereas visual feedback of the target and exerted force was removed (black bars) from 8–12 s and 16–20 s (no visual feedback condition). B) Respiration training: subjects were instructed to do the following: (a) control their respiration rate by inhaling through their nose with the same rate the horizontal bar was becoming red (dark grey) from left to right and exhaling through their mouth when the horizontal bar was becoming green (light grey) from right to left; (b) control their inhalation amplitude by inhaling through their nose and matching the target on the top vertical bar that was becoming red from bottom to top (towards the targeted line); (c) control their exhalation amplitude by exhaling through their mouth and matching the target on the bottom vertical bar that was becoming green from bottom to top (towards the targeted line).