Mechanical response of tendon subsequent to ramp loading to varying strain limits

limit of avian flexor tendons utilizing more current methodologies. Design. Assess the mechanical changes between subfailure and subsequent failure ramps at various loading levels. Background. Currently accepted values of elastic strain limits were determined utilizing older methodologies. Consequently, reported values are fairly small and imply matrix damage occurs with small strains. Methods. Flexor tendons were loaded in vitro, to various subfailure strain levels between 1% and 14%, allowed to rest for 5 min, then taken to failure. Suture markers, across the midsubstance, and cryo-grip displacement were monitored for strain using a video strain analysis system and a linear variable displacement transducer, respectively. The mechanical changes between the various subfailure and failure ramp loadings were assessed. Results. Varying strains of subfailure ramp loading did not influence (P>0.05) the ultimate tensile failure strength, elastic modulus, strain at failure, or strain energy density of tendons. In addition, residual strain after subfailure loading was not significant, nor was it influenced by the level of the subfailure loading. Conclusions. Tendon behaves elastically under ramp loading to significantly higher strains (nearly failure) than previously reported (4%).