PMID: 591919Dec 1, 1977

Mechanical control of the rising phase of contraction of frog skeletal and cardiac muscle

The Journal of General Physiology
E Bozler


The effect of shortening on contractile activity was studied in experiments in which shortening during the rising phase of an isotonic contraction was suddenly stopped. At the same muscle length and the same time after stimulation the rise in tension was much faster, if preceded by shortening, than during an isometric contraction, demonstrating an increase in contractile activity. In this experiment the rate of tension rise determined in various phases of contraction was proportional to the rate of isotonic shortening at the same time after stimulation. Therefore, the time course of the isotonic rising phase could be derived from the tension rise after shortening. The rate of isotonic shortening was found to be unrelated to the tension generated at various lengths and to correspond closely to the activation process induced by shortening. The length response explains differences between isotonic and isometric contractions with regard to energy release (Fenn effect) and time relations. These results extend previous work which showed that shortening during later phases of a twitch prolongs, while lengthening abbreviates contraction. Thus the length responses, which have been called shortening activation and lengthening deactivatio...Continue Reading


Mar 1, 1975·The Journal of General Physiology·E Bozler
Feb 1, 1976·Circulation Research·F J Julian, R L Moss
Aug 1, 1972·The Journal of General Physiology·K L Briden, N R Alpert
Sep 1, 1972·The Journal of General Physiology·E Bozler
Nov 1, 1973·The Journal of General Physiology·E Bozler, J F Delahayes
Jan 1, 1970·The Journal of General Physiology·S Winegrad

Related Concepts

Myocardial Contraction
Physical Stimulation
Ventricular Function

Trending Feeds


Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Genetic Screens in iPSC-derived Brain Cells

Genetic screening is a critical tool that can be employed to define and understand gene function and interaction. This feed focuses on genetic screens conducted using induced pluripotent stem cell (iPSC)-derived brain cells. It also follows CRISPR-Cas9 approaches to generating genetic mutants as a means of understanding the effect of genetics on phenotype.

Alzheimer's Disease: MS4A

Variants within the membrane-spanning 4-domains subfamily A (MS4A) gene cluster have recently been implicated in Alzheimer's disease in genome-wide association studies. Here is the latest research on Alzheimer's disease and MS4A.

Pediculosis pubis

Pediculosis pubis is a disease caused by a parasitic insect known as Pthirus pubis, which infests human pubic hair, as well as other areas with hair including eye lashes. Here is the latest research.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.

Rh Isoimmunization

Rh isoimmunization is a potentially preventable condition that occasionally is associated with significant perinatal morbidity or mortality. Discover the latest research on Rh Isoimmunization here.

Pharmacology of Proteinopathies

This feed focuses on the pharmacology of proteinopathies - diseases in which proteins abnormally aggregate (i.e. Alzheimer’s, Parkinson’s, etc.). Discover the latest research in this field with this feed.

Enzyme Evolution

This feed focuses on molecular models of enzyme evolution and new approaches (such as adaptive laboratory evolution) to metabolic engineering of microorganisms. Here is the latest research.

Alignment-free Sequence Analysis Tools

Alignment-free sequence analyses have been applied to problems ranging from whole-genome phylogeny to the classification of protein families, identification of horizontally transferred genes, and detection of recombined sequences. Here is the latest research.