Abstract
Stiffness of the upper arm muscles after physical exercise was measured objectively and quantitatively with a newly devised muscle hardness meter. Many studies about muscle stiffness have concerned stiffness caused by rheumatic disease or stroke which was estimated by patient questionnaire or palpation or was defined as the rate of longitudinal extension produced by a given force. These types of stiffness differ from the muscle stiffness that is felt after physical exercise. A newly devised muscle hardness meter was able to measure the depression in a muscle made by applying pressure to the muscle fiber in a direction perpendicular to its long axis. The following results were obtained. 1) The hardness of the extensor digitorum was significantly increased immediately after physical exercise and then decreased later. 2) The hardness of the biceps was significantly increased after two kinds of physical exercises then decreased. These results indicate that muscle hardness measured by this newly devised muscle hardness meter objectively and quantitatively reflects the muscle stiffness that is felt after physical exercise. This muscle hardness meter should prove useful in both medicine and athletics.
