The ultrastructure and tenderness of highly cold‐shortened muscle

Abstract
Summary: In an attempt to explain the paradoxical tenderizing, observed when muscle shortening exceeds about 40% of the initial excised length, the fine structure of highly cold‐shortened muscle has been studied by light and electron microscopy. Tissue at the ‘peak’ of toughness is uniformly shortened and shows no sign of structural weakness or damage, but with further shortening super‐contraction and node formation take place in an increasing proportion of the sarcomeres. Widespread fibre fracturing is seen in the internodal zones when the length change has exceeded about 50%. This disruption appears sufficient to account for the declining toughness which accompanies supra‐physiological shortening.