Glycolysis involved in glycolysis. The burning sensation in muscles during hard exercise can be attributed to the release of hydrogen ions during the shift to glucose fermentation from glucose oxidation to carbon dioxide and water, when aerobic metabolism can no longer keep pace with the energy demands of the muscles. These hydrogen ions form a part of lactic acid. The body falls back on this less efficient but faster method of producing ATP under low oxygen conditions. This is thought to have been the primary means of energy production in earlier organisms before oxygen reached high concentrations in the atmosphere between
Stiffness is dependent upon various physical dimensions that describe that component. That is, the modulus is an intensive property of the material; stiffness, on the other hand, is an extensive property of the solid body that is dependent on the material "and" its shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness is where Similarly, the torsional stiffness of a straight section is where Note that in SI, these units yield formula_6. For the special case of unconstrained uniaxial tension or compression, Young's modulus "can" be thought of as a measure of the stiffness