Fig. 5. Coupling of stiffness and damping in the body and notochord of hagfish during dynamic bending. (A) As flexural damping C increases, flexural stiffness EI decreases. Parameterized within the power curves (see Table 6) is driving frequency . (B) The maximal bending moments produced by stiffness and damping are directly and linearly proportional (see Table 6 for equations). (C) Experimentally derived values for the ratio of stiffness moments to damping moments change minimally, compared to theoretical ratios assuming constant EI and C (dotted lines), as changes (see Table 6). If is equal to the resonance frequency, the ratio is a special case of Equation 1, and estimates the maximum possible amplification of internal stresses. Filled squares, the `intact' structural treatment category; open squares, the `skin removed' category; open circles, the `notochord' category; filled circles, the `core' category.