  The maximum force that a crawling cell can exert on a substrate is a quantity
of interest in cell biomechanics. One way of quantifying this force is to allow
the cell to crawl against a measurable and adjustable restraining force until
the cell is no longer able to move in a direction opposite to the applied
force. Fukui et al.[1] reported on an experiment where amoeboid cells were
imaged while they crawled against an artificial gravity field created by a
centrifuge. An unexpected observation was that the net applied force on the
amoeba did not seem to be the primary factor that limited its ability to climb.
Instead, it appeared that the amoeba stalled when it was no longer able to
support a pseudopodium against the applied gravity field. The high g-load bend
the pseudopodium thereby preventing its attachment to the target point directly
ahead of the cell. In this paper we further refine this idea by identifying the
bending of the pseudopodium with the onset of elastic instability of a beam
under its own weight. It is shown that the principal features of the experiment
may be understood through this model and an estimate for the limiting g-load in
reasonable accord with the experimental measurements is recovered.
