Fig. 9. (A) Young's modulus plotted against the previous strain cycle value for each pH treatment. Threads treated at pH 5 and below show a pH-induced reduction in modulus that becomes less prominent as the thread is cycled to higher strain values. (B) Reduction in modulus (E) between strain cycles in Fig. 9A plotted against the strain that caused it for each of the pH treatments. Asterisks indicate where E at pH 5 is significantly different from E at pH 8 (P<0.01). Values are means ± s.e.m.; N ranged from 6 to 10 threads for each treatment.