Constitutive model of tendon responses to multiple cyclic demands (I) - Experimental analysis

The work reported here is an extensive study of tendon response to multiple cyclic tests including 3% constant peak strain level test (A-type test), 3 % constant peak strain level test with two rest periods (B-type test), and 3 similar to4% different peak strain level test (C-type test). A sufficient number of specimens were tested at each type of the test to statistically evaluate many changes in response during testing and differences in respons e between each type of the test. In cyclic tests, there were decreses (rela xations) in the peak stresses and hysteresis, increases in the slack strain s, and during lower peak strain level (3%) cyclic block after higher peak s train level (4%) cyclic block in the C-type tests. Considering the results of this study and those of the other study of multiple cyclic tests with re st periods by Hubbard and Chun, 1985, recovery phenomena during the rest pe riods occurred predominantly at the beginning of the rest periods. Consiste ntly in both studies, the effects of rest periods were small and transient compared to the effects of the cyclic extensions. The recovery with cycles at lower peak strain level (3%) after higher peak strain level (4%) in the C-type test has not been previously documented. This recovery seems to be a natural phenomena in tissue behavior so that collagenous structures recove r during periods of decreased demand.