Re: watch your step! - Trotting downhill

[TrotALongK <TrotALongK@aol.com>]

<< Not running fast down steep hills, ditto.  Although we trained for downhill
and would canter down mild slopes and trot down moderately steep ones; I would
get off for steep downhills.>>

I've been wanting to ask this question for a while, just kept forgetting about
it. John's post brought it back to my mind: 
How much downhill trotting is safe for my horse?
I live in the Santa Monica Mountains near L.A., those of you who've ever done
the Malibu Ride know that there isn't much flat ground around here. It's
either up or down, and in order to get a good, long work-out we have to trot a
considerable part downhill. I often get off and jog next to the horse (helps
the horse AND me...) and both my Arabs have learned well to balance themself
even on steeper trails, with or without rider. 
However, I've heard people say that "horses only have so many down hill
miles".
Is there any truth in this or is it more a matter of how carefully you choose
where and when to trot? 
I can imagine that this kind of exercise might cause a lot of stress on
tendons and joints. When do you know that you're over-doing it?  
On a typical conditioning ride (anywhere between 6 and 12 miles) I have about
1/3 to 1/4 of downhill trotting, some at an extended trot and some at just a
jog (depending on the terrain and the degree). I usually let the horse pick
what he's comfortable with. Should I be more conservative?   
How much down hill trotting do you do? And how fast? 

Kirsten