The origin of the instantaneous elasticity in single frog muscle fibres

Summary High-speed cinematographic recordings of single tetanized muscle fibres during a quick decrease in length revealed that the shortening was mostly localized at the fibre segment nearest the released end of the fibre, indicating that the instantaneous elasticity may not originate from the elasticity of the cross-bridges.We wish to thank Dr H. Hashizume of the Engineering Research Institute, Tokyo University for providing facilities to use the ultra high-speed cinecamera, and Mr T. Tsuno, Mr Y. Nakamura and Miss S. Gomi for their technical assistance.