Figure 3. Percentages of motor units recruited by the different tasks.

A, the percentages of motor units recruited during extension of thumb, index, middle, ring and little fingers (T, I, M, R, L) were determined for the motor units of each ED compartment (ED2, 3, 4, 5). The degree of shading of the grey bars indicates the force of the active digit at the time of recruitment (in blocks of 10% MVC; with darker shading signifying a higher recruitment threshold). When the instructed finger is the test finger (arrows), all motor units were recruited below 10% MVC, and further detail is shown in panel B. B, the columns of the test fingers in A are divided in lighter shades of grey to distinguish the recruitment thresholds of the test motor units in blocks of 2% MVC. C, the columns show the effect of ‘distance’ on the percentage of recruited motor units, including the data from extension of the thumb. The filled circles, connected by the line, show the same data without the data from thumb extension. Adjacent digits recruited more motor units than digits further away. However, for digits ‘4-away’ (thumb and little finger) there was major recruitment of little finger units by thumb extension.