The in-vitro caffeine contracture test: influence of the muscle histochemical profile on test results.

In vitro caffeine contracture tests were carried out on whole rat muscle composed primarily of either histochemical type I or type II fibers. Muscles composed primarily of type I fibers developed contractures at lower concentrations of caffeine and had lower caffeine specific concentrations than muscles composed primarily of type II fibers. These findings indicate that the histochemical profile of a muscle can influence the results of the in-vitro caffeine contracture test.