Vorticella convallaria is one of the fastest and most powerful cellular machines. The cell body is attached to a
substrate by a slender stalk containing a polymeric structure—the spasmoneme. Helical coiling of the stalk results from rapid
contraction of the spasmoneme, an event mediated by calcium binding to a negatively charged polymeric backbone. We use
high speed imaging to measure the contraction velocity as a function of the viscosity of the external environment and find that
the maximum velocity scales inversely with the square root of the viscosity. This can be explained if the rate of contraction is
ultimately limited by the power delivered by the actively contracting spasmoneme. Microscopically, this scenario would arise
if the mechanochemical wave that propagates along the spasmoneme is faster than the rate at which the cell body can respond
due to its large hydrodynamic resistance. We corroborate this by using beads as markers on the stalk and find that the
contraction starts at the cell body and proceeds down the stalk at a speed that exceeds the velocity of the cell body.