A study of the kinetics of the linear Ising chain has been carried out using as sole approximations the triplet closure and four kinetic equations. In particular, we have examined the effect of fluctuations of the number of uninterrupted sequences of the like elements by introducing a molar volume change ΔV associated with these fluctuations. Long range interactions and end effects can be partially accounted for by a suitable choice of the kinetic parameters. The theory is applied to the kinetic study of the helix-coil transition of polypeptides. For a relatively short poly-1-glutamic acid chain of molecular weight M = 12 000 (which is still long compared with the cooperativity length) the shift of the ultrasonic absorption peak due to relaxation 1 is accompanied by a non-negligible contribution of the absorption associated with a second relaxation. The theoretical results agree with existing measurements, and we have evaluated the volume ΔV