It can't keep still because its blood boils with energy. It runs through the fields and mountains all day to calm itself. If it doesn't, it can't sleep at night.
PokémonPoké.
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ProfessorProf.
Oak
Entry
Vigoroth are so full of energy when they are awake that they are always moving at least one part of their bodies. Their constant physical actions, including their fervent beating of their paws upon their chests, keep their muscles well developed.