Step Height

In article  whedon@netcom.com (Bill Whedon) writes:
> {how high is the step?}
>
>No risers = 4 inches
>One = 6 inches
>two = 8 inches

So far, so good.

>three = danger to your knees if you're average height and leg length

There is no research to back up this statement, and what little
there is refutes it, or at least calls the arbitrary and absolute
nature of it into question.

The primary problem with increasing step height involves avoiding
knee hyperflexion while the knee is weightbearing, in order to
give it the best mechanical advantage in lifting the body of the
exerciser, and also to minimize the compressive forces on the backside
of the patella.

The Step Reebok guidelines state that the exerciser should avoid
knee flexion of greater than 90 degrees while weight bearing, and
should shoot for 60 degrees or less if they have orthopedic problems.
Individuals with chronic knee problems are also advised to consult
with their physicians before beginning a step training program.

These numbers are not arbitrary - the 90 degree limitation is 
typically described as the "functional ROM" for activities of
daily living.  However, at 90 degrees of flexion the compressive
forces behind the patella are 2-3x bodyweight.  At about 60 degrees,
this is reduced to about 1x bodyweight.  For contrast, at 120 degrees 
of knee flexion, the compressive force is about 7x bodyweight.

More recent research on the issue of knee flexion and step training
looked at exercisers of varying heights and lever lengths.  Of all
the individuals in the study, none exceeded 90 degrees of flexion even
on a 12" platform (step+4 risers on each side).

In 1995, the Step Reebok guidelines were amended in two ways.  The
first was that the 12" step height was removed, and the maximum
height was reduced to 10" (3 risers).  The second was that it was
suggested that "the minimum step height necessary to induce a
training effect" be used.

[PERSONAL OPINION NOTE:  I imagine that the 12"->10" change has more
 to do with limitations of Reebok's current product offering than any
 real safety issue.]

While the new guideline acknowledges the potential for knee stress
(as the old one did), it does not make any arbitrary claims about
safety above or below a certain height.

> four = you're doing the ACE PT step test (or you better be...)

Picky point:  the "ACE PT" step test is actually the Harvard Step
Test, originally developed at the Harvard Fatigue Laboratory.  It has
been adopted by a great many organizations (including the YMCA and
ACE) as an inexpensive, relatively straightforward means of
estimating cardiovascular fitness.

It's actually only one of a series of bench-stepping protocols.  A
number of other protocols exists for both maximal and sub-maximal
testing, and the interested reader is referred to _Advanced Fitness
Assessment and Exercise Prescription_ by Vivian Heyward.

> six = a park bench

Or a bench press bench?  This is one of the things I love about the
blue benches that the new grey Reebok ones simply can't do.

					larry...


-- 
--------"It's my personal opinion that people need to be more clear about what 
	 is fact and what is in fact their personal opinion." -- me




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