  Natural human movements are stereotyped. They minimise cost functions that
include energy, a natural candidate from mechanical and physiological points of
view. In time-changing environments, however, motor strategies are modified
since energy is no longer conserved. Adiabatic invariants are relevant
observables in such cases, although they have not been investigated in human
motor control so far. We fill this gap and show that the theory of adiabatic
invariants explains how humans move when gravity varies.
