Figure 6. Force produced by the test finger at time of motor unit recruitment.

The mean (unintentional) force (±s.e.m.) of the test fingers (index, middle, ring and little fingers) is plotted at the time of recruitment during ramp extension contractions of the digits (T, I, M, R and L). The arrows indicate the condition in which the test finger is the instructed digit. Here, the force is the mean voluntary motor unit recruitment threshold and this force is also indicated by the horizontal dashed lines. Commonly there was a difference between the voluntary motor unit recruitment threshold and the unintentional force at the time of recruitment. When this difference is significant, it is indicated by an asterisk (P < 0.01).