Ken Roberts wrote:

Why? How?
What is it about the physics or biomechanics of rollerskis that makes them
more "specific" for backcountry skiing than inline skates?

Because you use a boot that flexes under the ball of your foot to
transfer power straight back, where blades will only allow you to kick
off at an angle to the line of the skate.

How many rollerskiers can make linked christie/parallel turns down a hill
like a good inline skater?

How many rollerskiers can make a long glide on a single ski and change
between the inside and outside edges 8 times like I can on inline skates (or
on a single backcountry snow ski going down a firm-snow slope).

And how many rollerbladers can use good straight ahead diagonal stride
to cover a lot of ground over the great majority of muscle use time
spent over a day?

Personally I use blades, but my friendly neighbourhood nordic instructor
and professional backcountry tour leader uses rollers in direct
preference because they're more like skis for the business ofbasically
covering ground. If you're in a steep up, steep down mode then I would
say they'd have little utility, but a lot of backcountry skiing is about
covering reasonably level ground in straight lines, which rollerskis can
help with better than blades.
My backcountry touring typically uses more nordic flat technique than
downhill with day's hut to hut in Norway typically involving single
figures of tricky turns, but double figures of kilometers following
tracks. YMMV.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/