legs for a few million years. We’d imagine that by now
we’ve figured out a pretty efficient mechanism for
getting around. Unconvinced, however, researchers at
Carnegie Mellon University have developed an “exo”-
boot that reduces the metabolic rate of walking by
seven percent. Best of all, the mechanism requires no
additional source of active power input besides the
human legs that are wearing them.
Upon close inspection, the boots reduce the overall
applied torque at the angle joint at a critical point
where the heel begins to lift off the ground. Energy in,
energy out. The spring ratchets to a loaded position as
the user plants their foot. This ratchet releases, re-
engaging the stored spring force as the user brings
their heel back off the ground. A seven percent
reduction in metabolic rate may not sound like much,
but, according to the paper, it’s the equivalent of about
four kilograms less weight in your backpack on that
next hiking trip.
As for what specific costs are being reduced to lower
the body’s metabolic rate, the researchers still aren’t
completely sure. An off-the-cuff look at the joints and
moments from a mechanics perspective won’t give us
a sure-fire answer since the energy consumption
processes of muscles are, well, complicated. In fact,
by varying spring stiffness in their design, they
discovered that springs that were either too stiff or too
loose had no effect on the metabolic rate. Yes, they’ve
certainly stumbled on a sweet spot in terms of well-
mixed circumstances, but the answer behind why
the new robot-legs work so smoothly will be a study for
the future.
If you haven’t jumped into the world of exo-skeleton
building, let [James Hobson] be your guide into pushing
our bounds with homebrew mechanical advantages.
Now let’s keep our fingers crossed for some long-fall
boots.