The major changes in the muscular metabolism manifest themselves in the first phase following the infection (up to about the 20th day). The main source of energy is then constituted by fat metabolism, whereas in the second one the sugar metabolism takes the upper hand. The activity of the Krebs cycle is also diminished, particularly that of fumarase enzymes, malic acid dehydrogenase and alfa-ketoglutarate decarboxylase, in contrast to the conspicuous increase in the activity of succinic oxydase, which might suggest a damage to the Keilin-Warburg system in the mitochondria.
The previous own studies on the metablism of Trichinella spiralis indicate that larvae utilize the sugar energy mostly through the mediation of pentose-phosphorus cycle, which also accounts for a slight participation of bi- and tricarboxylic acids in the parasite energetics. Phosphorylating glycolysis plays a negligible role. The respiration rate being affected to a comparatively slight degree by individual sugars, this would indicate that larvae might utilize their own sugar reserves or take up a reduced amount of examined sugars.