Relation between oxygen uptake and developed tension in dog skeletal muscle

Isometric developed tension of in situ gastro-cnemius-plantaris and semitendinosus muscles of the dog was increased 30% with twitch contraction frequency over the range of 0.5--2.0 tw/sc. Developed tension was decreased 75% after 30--40 min of 11--14 tw/s contractions, fatigue. Recovery from fatigue was slow. Intravenously injected K+ after fatigue increased developed tension 50%. Infusions of epinephrine, norepinephrine, and ouabain did not change developed tension. When the oxygen uptake of gastrocnemius-plantaris muscle was measured during twitch contractions at 0.5, 1.0, and 2.0 tw/s before and after fatigue and after injection of K+, the oxygen uptake was found to be directly related to the developed tension.