Fig. 6.

A: The neural control of a pair of opposing muscles can be described as a combination of λ values for the agonist (λAG) and antagonist (λANT) muscles. Alternatively, it can be described with the reciprocal command (r) and the coactivation command (c). B: formally, c-command can be negative when there is a range of joint angle where both muscles are quiescent.