Seat Height
The height of the seat can
have a very significant impact on the efficiency of riding.
In one study of short-term total power output, saddle height
was optimised at 109% of the inseam length (the distance
between the bone in the crotch and the ground, in bare
feet). While the experiment was quite specific in focus and
there is individual variation, on average an alteration of
saddle height of only 4% affected power output by
approximately 5%. This performance increase is about as much
as a guy I know who spent some $600 on new wheels with
streamlined, 16-hole rims and bladed spokes to shave 59
seconds off of his 15 km time trial.
Cycling is a repetitive
activity where the longtime cyclist becomes strongly
accustomed to a saddle height, so changes should be made in
small amounts and at long intervals, such as 1/4" each
month, towards the formula result. Large variations in
saddle height can be compensated by the degree and even
direction of ankling.
 In general, you want your leg
at maximum extension to bend by 25 degrees. Less won't allow
your leg muscles to operate near maximum extension where
they are most efficient, and more disrupts your pedalling
stroke and the health of your knees as well. Similarly, if
you rock back and forth in the saddle, the saddle is too
high.
Women, with their longer
legs, will want a higher saddle than a man who is just as
tall. When you find your perfect saddle height, mark your
seat post and periodically check it, as your seat post will
slowly sink into the tube over time. And be sure to record
your bike's adjustments to it can be reliably duplicated if
your bike gets mangled when you try to ship it to a race.
For the trail
Mountain bikers who ride on
rough trails may want to lower their seat just a little, as
they spend a large amount of time out of the saddle, going
over bumps.
Also trail riders should make
use of their quick release seat-posts and adjust the height
during the ride if need be, for extended steep downhills or
extremely bumpy terrain. Just make sure that you put the
post back to the marked normal optimum, so you can quickly
switch back at the bottom of the valley.
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