The way you swing

-- OUR nomadic ancestors had to quickly
cover long distances while hunting. A
prey that ran faster had to be outrun.
While running after the animal they
constantly moved their arms; it reduced
the effort and counterbalanced the body
weight. People now run after buses,
sprinters run to win a medal. But the
dynamics of running have not changed.
What a team was interested in knowing
was why humans swing their arms even
while walking.

The researchers from the University
of Michigan, USA and Delft University of
Technology, Netherlands, studied arm
swinging that goes into a walk and concluded
that it is an energy conservation
measure. If humans do not swing their
arms normally while walking, they will
burn more energy. Health enthusiasts
who take early morning walks in parks
to lose some flab should change the way
they swing their arms.

The team developed a walking
model to test its theory. Even with no
force driving it, the model easily produced
a walking gait similar to humans.
When the model swung its arms in a
way that opposed the normal mode of
walk, it required muscular effort. This
proved that swinging arms normally
while walking requires little muscular
effort. Whether it yields energetic benefits
or not the team found out next.

Ten people were asked to walk in
four ways: normally, arms clamped by
the sides, arms held loosely by the sides
and arms swinging anti-normally. In the
anti-normal mode, the right arm moved
with the right leg and vice-versa.

Barring the normal swing, the body
burnt energy in all the other modes.
Metabolic rate was the lowest in the
normal walk. It increased 7 per cent in
bound condition, 12 per cent in the held
position and was 26 per cent greater
than normal in the anti-normal mode.
"Swinging one's arms normally does
indeed save energy. To get better exercise,
one could swing them in the opposite
direction. This is not the funniest
way to burn calories," said Steven H
Collins, key scientist of the study and
from the Michigan University. "Our
interest is in saving energy for patients
with gait disorders who use too much
energy as it is," he added. The study is in
the August issue of Proceedings of the
Royal Society B.