Infrared thermography of bullfrog skeletal muscle at rest and during an isometric tetanus

Heat production in skeletal muscle has been studied with a thermopile consi sting of several thermocouples in contact with muscle surface, and the expe rimental results have been interpreted on the assumption that heat is produ ced in a uniform manner. In the present study we have examined the temperat ure distribution of bullfrog sartorius muscle by the technique of infrared thermography, in which muscle temperatures at various regions can be measur ed and displayed as a thermogram on the monitor screen without thermal cont act. It was found that in the muscle at rest and during an isometric tetanu s, the temperature was not uniform, but differed from region to region. The amount of heat production during an isometric tetanus also differed from r egion to region, but the time course of heat production was nearly uniform in every region. By putting position markers on the muscle surface, it was possible to record muscle segment length changes together with temperature changes. It was found that during an isometric tetanus, the tibial region w as stretched by the other regions, and the amount of heat produced was sign ificantly greater in the other regions than in the tibial region. The appli cation of infrared thermography in muscle energetics studies seems promisin g if the sensitivity of infrared detectors is improved.