Spatial and temporal stepping parameters have been studied in a rocklobster walking on a treadmill moving at a wide range of speeds. The stride and the return stroke (RS) duration remain more or less stable and independent of the belt speed. Nevertheless, these ‘invariant’ parameters can act as spatial and temporal buffers resulting in a very precise adjustment of individual steps.
A careful study of the power stroke (PS) duration demonstrates that the rock-lobster, although constrained to walk at an imposed belt speed, continues to correct its leg speed over a narrow range when the speed is considerably different from its natural one. Ipsilateral phases are always speed dependent, with an interleg ascending delay that is almost constant. The contralateral phase between legs of the same pair is approximately constant.
Some of the parameters described are greatly influenced by gradual or abrupt variations in the belt speed. For a given speed, there is no absolute significance in the step period and ipsilateral phase. At very slow speeds, the interleg relations are significantly changed and have been studied separately. The metachrony observed at other speeds is discussed in relation to data from other arthropods.