How will we walk? SLOWLY

On Sat, 11 Sep 2004 19:50:25 -0000, bparkyn wrote:
> Computer simulations are better than harness experiments, which
> merely reduce foot traction but do not account for the lower pendulum
> frequency. Such studies show that the walking speed on Mars is only
> 1.5 mph, with any higher speed requiring a jog. Of course, we all
> know that on the Moon the astronauts ended up with a skipping hop as
> locomotion. While this is not as big a problem as reduced immune
> system functioning, it still counts against low-gee living.
(...)

By the way, I have often read that "microgravity depresses the imune
system", but another day a friend of mine just pointed out: "But what
if it is caused by radiation, not microgravity?". Then I realized
that, as far as I know, *all* experiments involving humans in orbit
also involved much higher levels of radiation; there was never a
shielded habitat where the radiation factor was eliminated.

So, since high levels of radiation are a known immuno-depressive
factor, how exactly did the studies conclude that zero-g, and not
radiation, was the main responsible for the immuno-depression observed
in astronauts?