A friend of mine was talking to me recently about coming down the Incline with his son and how he felt by the end of it, having not done the Incline in over a year.  He said his knees where killing him and toward the bottom where the Incline's grade decreases slightly and he could keep up a slow run he could feel every foot strike.  Now let me start by saying I do not condone trespassing, if/when the Incline is legalized ALL rules should be followed to the t and if using the Incline (or any trail for that matter) everyone needs to remember that basic trail etiquette is UPHILL traffic has the right of way (except in an organized race when downhill traffic has the right of way), and YOU are responsible for staying in control of your speed and body at all times on the trails.    With that disclaimer out of the way let me get to my point, which is back to the conversation with my friend when he asked me my opinion on coming down the Incline.  As a trail runner and a trainer I think that the Incline can provide a great workout, both up and down.  The up portion is obvious, although every time I am out there I see people not really taking advantage of the workout they could be having by committing some basic training errors and form issues.  The down portion can be a great workout if done correctly and safely, the first and most important rule is stay in control of yourself and be courteous and cautious of others.  I say this after two personal experiences of almost being taken out when someone was running out of control down the Incline and fell, both times missing me and my exposed and vulnerable knee by inches.  If done properly coming down the Incline helps to build your core and leg muscles as you are constantly engaging your core and your legs are going through concentric, eccentric, and isometric muscle contractions continuously in an attempt to keep your body in control and upright.  This type of workout is the premise for a lot of today's new and popular workouts and workout equipment.  The parts of the Incline where you can safely speed up and run  (again IN CONTROL)  test your foot/eye coordination, your foot speed, and allow for you to adopt a running style that mimics a barefoot running style, striking with your forefoot and absorbing the shock up through the kinetic chain as opposed to pounding the ground and letting your joints absorb the shock and weight.  This is safer for you, helps you to maintain control, and creates a lot less impact on the Incline itself, not doing this is the mistake my friend made coming down and why his knees hurt so badly.  I certainly would not suggest attempting to come down the Incline if you are not comfortable with the exposure, or if you are too tired or inexperienced to do it safely.  Falls on the Incline are a very serious matter, take it from someone that has fallen on the Incline and also fallen on normal trails, on mountain bikes, road bikes, skiing, and climbing; a small fall on the Incline is a big deal!  But if done properly and safely using the Incline in reverse can be a great training tool.