RC: RC: Re:overweight an issue?

["Jana Crewett" <jfcr@ceh.ac.uk>]

>Jana Crewett wrote

Wolfgang wrote:
>You are German???

;-) - anything wrong with that?? (I live in the UK though, so maybe I
don't count...)


<big snip>
>I have emailed to ERASA to get in contact with Dr. Loukie Viljoen
and ask
>for an update of that study as well as for more data. I'll keep you
>informed.

Thanks - this is starting to get interesting!


>> ...snip.. One obvious one would be that heavier riders
>> might, on average, be older and less competitive, riding for
>> completion rather than racing for top ten and thus obviously
achieving
>> lower speeds.

>I don't think so. The Gold Medal Team of New Zealand at the WEC 1998
had
>an average age of ~ 55 or even older. And they didn't ride for
completion.

;-) - I didn't say there aren't some fast oldies about! 
Stated a bit more precisely, I meant that among the group of riders
who choose to ride slowly and aim for completion rather than for top
ten speeds (regardless of whether their horse would be capable of
going faster or not), there will probably be a disproportionately
large group of middle-aged to older people, and as these people will
also on average be heavier than younger people, this factor might have
strongly influenced the result that "heavier riders achieve slower
speeds". 

It was really just an example of how an outside factor that affects
speed could skew the result if this factor is not explicitly taken
care of.  There are probably hundreds more of these "outside
influences" out there (heavier riders might mainly be men, who might
have on average less riding experience than women due to the "horse
culture" in the west being mainly female-dominated and hence might be
less balanced riders; heavier riders might on average be less
physically fit; (heavier) men might on average work longer hours than
(lighter) women and thus have less time for training their horses;
...) - if one does not look at these factors specifically, one will
never know whether they contribute to the results or not. 
Please note I am only speaking of "averages" - this does not rule out
the existence of balanced, superfit 100kg male riders who do lots of
training, it simply means that for these subgroups the bell curve is
slightly shifted, which will show up when one examines a large sample
and which will lead to "sample artefact" effects one has to be aware
of.

I guess this is a fundamental problem of laboratory vs field data -
either one has controlled treadmill experiments (which are dubious on
their exact implications for real world situations) or one uses real
world data but then has to deal with statistically "difficult" sample
artefacts and lots of uncontrollable parameters.


Jana