What it is
In 1984 Alois Mader proposed a mechanistic model of muscle energy metabolism: 33 coupled differential equations linking oxidative phosphorylation, glycolysis and the phosphocreatine shuttle through ADP, phosphate and pH feedback. The authors release MetaboliSim, open-source software that runs the model in a virtual human described by four inputs (oxidative capacity VO2max, glycolytic capacity vLamax, body mass and active muscle mass), and test it against 10 experimentally established phenomena of exercise metabolism without changing any equation or constant. The model qualitatively reproduces all 10, among them ATP homeostasis under fatigue, transient pH alkalinization, glycogen-dependent lactate thresholds, the inverted-U of fat oxidation and the slow component of oxygen uptake.
Why it matters
Wider use of Mader's model had been held back by closed-source implementations and key publications available only in German. That a compact, 40-year-old equation system accounts for this breadth of phenomena suggests, the authors argue, that a small number of regulatory feedback loops may suffice to explain a wide range of metabolic responses to exercise, and the free tool lets others test, calibrate and refine it.
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Filed underCardiovascular and exercise physiology, Muscle metabolism and nutrition, Sports Performance and Training