Effects of acidosis on tension development in mammalian skeletal muscle.

Effect of carbon dioxide acidosis on the tension development in a rat skeletal muscle (extensor digitorum longus) was examined at different temperatures. Experiments were done in vitro and with direct stimulation, mostly at constant temperatures between 30-35 degrees C and 12-20 degrees C. A decrease of saline pH (8.0 to 6.5) with carbon dioxide increased the twitch and the tetanic tensions and enhanced the tension relaxation in experiments done at high temperatures. At low temperatures the same procedure decreased the tetanic tension and enhanced the tension relaxation. An increased tetanic tension at the high temperatures and a decreased tetanic tension at the low temperatures were also obtained at constant saline pH, with procedures known to decrease intracellular pH. The observations made at higher temperatures are discussed in relation to human muscle performance in exercise.