Fig 1.
A: Experimental setup. Participants were seated with their right index finger and their left foot reaching comfortably the force transducer and the response button, respectively. Auditory stimuli were provided via loudspeakers. B: the visual feedback that was provided on the screen representing the applied force (blue line) and the target force level (red lines). C: An example of a time-series showing perturbations from the dual task condition. Participants were instructed to maintain a given force level (applied force: blue line) and to react (green line) as quickly as possible when hearing the auditory beep (red line).
Fig 2.
Representative force-time-series showing a typical perturbation profile. The criterion for the perturbation detection was defined by values crossing the mean of a 1 s baseline before the tone ±2 SD of the baseline. Based on this criterion, first, the perturbation upward is detected and expressed in amplitude relative to the prescribed force level; second, the downward perturbation is characterized in the same way. Based on the amplitude and the relaxation time, i.e., the time from the peak amplitude of the downward perturbation till the force reaches the perturbation criteria again, we calculated the rate of relaxation.
Table 1.
General properties of force production.
Fig 3.
General properties of force production.
A: Mean force, standard deviation, signal-to-noise ratio, and SampEn as a function of force level plotted per group for the single and dual task comparison. B: the comparison before and after the perturbation. C: the relative amplitude of the up- and the downward perturbation, the relaxation time, and the rate of relaxation. Additionally reaction times were plotted as a function of force level. Each data point represents a group mean. Error bars represent the standard deviation.