To the Editor.
—The Editorial entitled "Isometric Exercise Testing: Usefulness and Limitations" by Dr Stefadouros, published in the January Archives (1983;143:26-27), began with a statement that brought me up short: "... Isometric exercise [is] a form of exercise where the contracting muscles develop force without shortening." Can this be so? Can muscles develop force without shortening? I don't think so.There are at least three things that a muscle can do (1) contract, (2) relax, and (3) be stretched or compressed by external forces. When a muscle contracts, it shortens and thickens; there is nothing else it can do. If its action is opposed, its tendon or point of insertion may not be moved, but the muscle itself has shortened. In the example cited—the use of a handgrip dynanometer—we are talking about the use of an instrument "that is manually squeezed by the patient." There is no way that I can
Simmons VP. Isometric Exercise Testing. Arch Intern Med. 1983;143(8):1631-1632. doi:10.1001/archinte.1983.00350080153039