Side Push or Forward Push
Both explanations can be correct. They describe two different ways of organizing spiral or circular power（螺旋勁／圓勁）. Neither is automatically more powerful.
The important question is not simply “side push or forward push?” but:
Does the circular force enter the opponent’s center and disrupt his root?
圓勁是否進入對方中軸，破壞其根？
1. Pushing diagonally from the side toward the center
When you push from the side toward the opponent’s center, you combine:
forward power（前進勁）
rotational power（旋轉勁）
lateral displacement（橫向移位）
The contact point travels along an arc. Your waist and kua rotate while the body advances, so the resulting force is a vector composed of forward and rotational components.
This is often more effective than a direct push because you are not confronting the opponent’s strongest structural line head-on. You approach his center from an angle and make his body turn while also moving backward.
A simple model is:
However, combining directions does not create free energy. If the same total effort is divided into forward and sideways components, the net magnitude does not magically increase. It becomes more effective because:
the opponent cannot align his bones directly against it;
rotation makes his two sides unequal;
one kua or foot becomes overloaded;
his center is moved outside his base;
his reaction becomes slower.
Therefore, it is often better at uprooting（拔根）, even if it is not physically a larger force.
This agrees with:
避實擊虛 — avoid fullness and attack emptiness.
引進落空，合即出之 — lead the incoming force into emptiness, then issue when the bodies join.
2. A “straight” forward push using a vertical circle
A good Tai Chi forward push is rarely a flat, horizontal shove. It often contains a hidden vertical circle（立圈）.
The hands may appear to travel forward, but the internal path is something like:
The feet receive the ground reaction.
The legs extend without stiffening.
The kua and waist transmit the force.
The back expands.
The elbows settle while the hands move slightly upward and forward.
The arc completes into the opponent’s center.
Therefore, the visible direction is forward, while the internal movement follows a vertical arc:
外形似直，內勁走圓。
Outwardly straight; internally circular.
This corresponds closely to the classics:
其根在腳，發於腿，主宰於腰，形於手指。
It is rooted in the feet, issued through the legs, directed by the waist, and expressed through the fingers.
And:
由腳而腿而腰，總須完整一氣。
From the feet through the legs to the waist, everything must be completely connected as one qi.
The slight upward component is not meant to lift the opponent with the arms. It enters under his structure, raises or lightens his root, and then carries him forward or backward.
This is related to:
掤勁（peng energy） supporting upward and outward;
按勁（an energy） advancing forward and slightly downward or upward according to the situation;
沉中有升（rising within sinking）;
借地力（borrowing power from the ground）.
3. Which is more powerful?
They have different advantages.
| Method | Main circle | Strongest quality | Best situation |
|---|---|---|---|
| Side-to-center push | Horizontal or oblique circle（平圈／斜圈） | Turning and uprooting | Opponent is firmly braced forward |
| Forward push with vertical circle | Vertical circle（立圈） | Ground-connected penetration | You already control his center |
| Pure arm push | Little whole-body circle | Local muscular pressure | Usually the least effective |
If “powerful” means maximum force
The forward vertical-circle push can often transmit greater force because the feet, legs, hips, spine and hands align behind one principal direction. Less energy is diverted sideways.
If “powerful” means easiest to move the opponent
The side-to-center rotational push is often more effective because it attacks a weaker angle and generates torque:
Here, is the distance from the opponent’s central axis. The farther your effective contact is from his axis, the more turning effect the same force can produce.
So:
The straight method may deliver more force; the angled method may require less force.
That is a very important distinction in Tai Chi.
4. The two methods should not really be separated
The highest-level action usually contains both.
A side-to-center push should also be rooted in the feet and contain a vertical circle. Otherwise, it becomes only a twist of the waist.
A forward push should also contain rotation. Otherwise, it becomes a stiff two-handed shove.
The body naturally produces several circles simultaneously:
vertical circle（立圈）: ground → legs → spine → hands;
horizontal circle（平圈）: waist and kua rotation;
oblique circle（斜圈）: diagonal connection through opposite foot and hand;
spiral（螺旋）: rotation traveling through the limbs.
The resultant force may look straight even though it is produced by circles:
螺旋而進，合力於一點。
Advance spirally and unite the forces at one point.
This fits the classical principle:
運勁如抽絲。
Move energy as though drawing silk.
And:
立如平準，活似車輪。
Stand like a balanced scale; move like a wheel.
The “wheel” is important: a wheel rotates, yet the part touching the ground can transmit a strong linear force.
5. The most powerful sequence
In practical push hands, the strongest method is usually:
Sink and connect to the ground（沉、接地）
Rotate the waist and kua（腰胯旋轉）
Enter from the weak angle（避實擊虛）
Aim through the contact point toward his center（力點透向中軸）
Let the vertical circle lift or loosen his root（立圈拔根）
Unify the vectors and issue forward（合力前發）
Thus the horizontal or oblique rotation first compromises his structure; the vertical circle then receives ground force and completes the issue.
It is not:
rotation versus forward force.
It is:
rotation creates the opening; ground-connected forward force passes through it.
旋轉開門，前勁入中；立圈接地，合力而發。
6. A useful test
Do not judge the method by how strongly your arms feel. Test three things:
Does your shoulder remain released（鬆肩）?
Can the pressure be traced to your rear or supporting foot（力達於根）?
Does the opponent’s center move before your hands visibly push（先動其根）?
If your hands move first and your body follows, it is an arm push.
If the ground, legs, waist and hands arrive together, then even a small movement can be powerful:
整勁勝於局部力，得機得勢勝於力大。
Integrated power surpasses local strength; timing and position surpass brute force.
So my conclusion is:
A forward push using a true vertical circle generally has greater potential force. A side-to-center spiral is usually more efficient for breaking balance. The most advanced push combines both—horizontal rotation to expose the center, a vertical circle to connect with the ground, and forward intention to issue through the opponent’s root.
