I have just noticed the question. Indeed, the body does have very clear resonances. Nature has prioritised speed of movement over stability so limbs are underdamped and naturally resonant. It is likely that many rhythmic movements occur at the resonant frequency of the body parts involved (rather similar to the oscillation of some insect wings). A complication is that, like many biological tissues, muscles are very non linear and are actually much stiffer for small displacements than for large ones. This means that, for example, the resonant frequency of the human wrist is about 2 Hz for large oscillations but rises to ~ 10 Hz for small ones. There is some physiological literature on this subject - my late colleague and friend EG Walsh described some of it in his book, Muscles masses and Motion (1992, CUP). More recently I have been very interested in the contribution of resonance to the small, normally unnoticeable tremor that all humans have.