Fig. 6. Linear relationship between the maximal rotational velocity of the tibia during a kick and the number of spikes in the fast extensor tibiae motor neurone (FETi). The greater the number of spikes, the higher the speed of rotation, but there is variation in speed for a given number of spikes in different kicks. Data from 45 kicks by six Pholidoptera are pooled. The line was fitted by linear regression y=0.83+8420x (P<0.001, r²=0.78).