In the rock lobster Palinurus vulgaris the activity of two mechanoreceptors is compared; one is a chordotonal structure, MC1, the other is myochordotonal, MCO1; they are functionally associated with the same joint (M‐C: merus‐carpopodite) of walking legs. We have compared the afferent activity of MC1 and MCO1 during joint movements and during isometric contractions of the flexor muscles induced by the stimulation of their motor nerve in order to determine their respective sensitivities to different kinds of mechanical stimuli. MC1 records both movement and position of the M‐C joint; the possibility that it records muscular tension is discussed but this appears very restricted. In contrast MCO1 activity is increased by movement of the joint and by the contraction of the proximal part of the AF muscle. The findings confirm that the term mychordotonal is appropriate and is conferred by its very original properties.