ABSTRACT
Skeletal muscles present a static tension: an increase in force after stretch that is dependent on Ca2+ but independent of myosin-actin interactions. This chapter presents the main characteristics of the static tension and discusses the proposed mechanisms responsible for this phenomenon. Evidence will be presented showing that the static tension is caused by a Ca2+-induced increase in the stiffness of titin during activation and stretch. Such increase in titin stiffness increases the overall sarcomere stiffness for as long as muscle activation persists. This form of Ca2+ regulation has important implications for our understating of the basic mechanisms of muscle contraction.
