as navyvet mentioned, part of riding the motorcycle
is potential for all of body movements, small openings
and closing of joints with small stretching of connective
tissues, which can have an overall relaxing effect..
esp in [eg] rides with curves, speed changes,
ongoing use of brakes, clutch and gears
plus fine but ongoing head and eye movements
[many small muscles move eyes, face]
which are relatively non taxing of the body
but can have nice effects similar to yawning
reflex stretching..
on highway runs upright constant speed etc,
natural responses to leaning, turning and so on
are largely absent, so, we can still move our bodies
joints muscles etc within typical highway riding
styles.. just taking one hand of its bar and stretching
the back upwards say, is an easy example of this..
tucking, and associated movements, same same..
on highway runs on my unfaired cb750 i would
sometimes rest my bent left arm on the tank
then rest my body and chin forward on that,
as a simple relaxing method, to allow tensions
in back neck etc to flow away into the position..
same same occasionally sitting up with stiff legs
pointed forwards [handy riding over water]..
and/or similar to the riders above in speed circuit
and bonneville racing, stretching legs backwards,
as if trailing behind in the wind and/or on rear pegs..
tucking gives aerodynamic advantages thus fuel
economy, but also directs wind buffeting away for
comfort.. if slowing then sitting up into wind
is another position change causing muscle
activation [esp upper back, shoulders, arms, hands]
but also acting as a wind brake, adding to braking
economy, or for strong slowing more efficiency..
within reason and according to experience etc
you can move the bike around even on a straight
road, sit up stretching occasionally, move legs
around, rest one arm, turn torso neck and head
around [motorcyclists should have good relaxed
upper torso and neck for easy balanced turning]
or the old favorite, standing up on the pegs..
often had a small carry bag on the tank of the 750
[clothing etc] which also acted as a pillow when
leaning forward over the tank, or 'tucking'..
incidentally, one result of yoshi rear set step plates
is moving of pelvis rearward to seat stop area
causing a natural slight tucking effect..
so you can and perhaps should
be tucking on your motorcycle...