The single whip basically attacks on the face. But, a “Low single whip (単鞭下勢)” is a technique to hit the palm like a whip, aiming at the groin.
Let’s explain the usage. You are taking a left leading stance (See Photo 1 below).
The opponent strikes the right fist to your face in the order of the right shoulder and the right leg forward. With deflecting their right hand with your right hand, you are stepping to the left side (See Photo 2 below).
Then, advance the left foot to the outside of the opponent, and hit the left palm like a whip in the opponent’s groin from the inside (See photo 3 above).
Simplified 24-form Taijiquan stemmed from Yang style Taijiquan takes a very low posture called “Lower Posture (下勢)”(See Photo 4 below).
Here one question arises.
What kind of skill is this in Yang style Taijiquan?
In Chinese martial arts, when taking a low posture, it is usually an unpredictable attack aimed at surprise attack. For example, turns your leg and hooks the opponent’s foot, or grabs sands from the ground. If you fail, there is a danger that you can be defeated by their low kick or brought to ground fighting. Taking a low posture on your own is nothing less than making the attack at all risks.
At a glance, this posture is vulnerably unguarded. However, if you could see an invisible sword that extends from your hand to the throat of the opponent, it would be in good shape as martial arts.
(See picture 4 below again)
What I learned is Chen-style Taijiquan. I merely imitated the lower posture of Yang-style Taijiquan. Please allow me to show one of the usage possibilities.
I think that there are some low postures are effective if you have a weapon like a sword, a spear, or a staff. But I want to say from my experience that it is better not to take a low posture in bare hands combat unless you intend to drive them into ground fighting.