Like Gyrobob said,.. body lean is a technique mostly reserved for racing...
... but, since you are talking about learning to push the limits, it's a good thing to know.
When your bike leans in a turn, it is balancing the forces of centrifugal force against gravity to keep you on the road. Shifting the total weight of you and your bike to stay on the road.
The distribution of the weight of your bike is fixed and the only way for it to balance is to lean more and more as the turns get tighter. Your body is not fixed on the bike... you can shift your weight from side to side.
This shifts the balance point of the bike. If you lean your body in a turn,... the bike will go more upright to correct the balance point.
This is particularly good to know when the pegs start scraping, because, once the peg is down, the next thing to touch will be solid and will put you down... lean your body while a peg is touching and the bike will go more upright and the peg will stop scraping.
I rarely scrape pegs, because as I feel that point approaching, I lean my body into the turn.
My shocks are also 2" taller than stock, so my scraping point is much more extreme than on a stock bike.
Because the stock bike scrapes fairly easily,... knowing that you can lean in to stop it is even more important...
I wouldn't recommend riding at that extreme as matter of habit,... but if you find yourself caught off guard by a decreasing radius turn,... knowing to lean your body into it can save your skin...
This guy takes his practice seriously...
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PS...
a cager,... is a car driver with no awareness of motorcycles...
a bug up the butt,... is an irresistible urge to do something stupid...
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