CBM is used to precede any curved step.
Contra Body Movement (CBM) is a critical concept used to initiate or prepare for a change in direction while dancing and is commonly defined as:
"Turning the opposite side of the body toward the moving foot"
Despite this, dancers often find CBM:
CBM is a term used to describe your shoulder rotation with regards to your moving leg. CBM is a consequence of something else happening No, you can't "do CBM", ok, ok you can but it's not going to look or feel that great and worst of all, it won't accomplish what you want.
The various Syllabi and other Books proclaim: "CBM happens on step (or beat) 1 (and sometimes other beats)."
The established syllabi manuals say "CBM on 1" meaning "at the start of beat (or step) 1" (which in turn raises the issue of when 'beat 1' starts). This can (and usually does) result in teachers struggling to explain the timing and amount of rotation often resorting to “just do it like this” demonstrations.
While traditional syllabi list the beat where CBM occurs, they often omit key details such as:
all of which are essential to executing CBM
\(\vec{T}\) is just a symbol used to show a direction. Nothing scarey.
Let’s suppose the Leader rotates their frame fully on beat (i.e Step) 1 — a clean, textbook 45° of CBM. The Follower will rotate ideally by the same amount.
That means:
The Leader's \(\vec{T}\) is now at a -45° angle (i.e DC) to the original direction of travel (e.g., FLOD).
The Follower, in closed position, mirrors this rotation due to frame contact.
But the Follower’s step 1 is backwards — and now they’re moving diagonally backward toward the center of the room — a completely different \(\vec{T}\).
This can create:
Divergent travel paths where Leader and Follower are trying to go indifferent directions,
Likely misalignment of foot placements depending on the offset and gap between the dancers,
Awkward, jerky weight transfers for both dancers.
“You cannot have a 45° frame rotation on without influencing the direction of travel.”
If the Frame is rotated the Follower will start to go in that direction especially if their free leg can move in the direction of the rotation.
OK, you can dance it like that but it's not going to feel great and it's going to be a really bad experience for new dancers. It's also a cause of "my partner feels heavy".
Another factor is the Partner Gap and Partner Offset
Even without math (yet), the moment the Leader turns their torso 45° before the Follower has committed weight backward, the resulting frame sends the Follower off-course. The rotational vector overrides their stable backward path — and biomechanically, they either resist the frame or get flung into an off-axis step. The Leader will synchronize with Followers new position and now they are heading in a different direction than Leader had intended.
As we proved in the Curved Travel, there are no curved steps. All steps are linear, they are in a straight line and are vectors. Don't panic about that word as it really is your friend.
Leaders left foot travels forward, followers right foot travels backwards and they 'turn left' which is why we have "CBM on 1" to move the Follower out of Leaders way. Except we aren't turning left, it's the last thing we want to do. We want our bodies to face left so we can travel in a different direction.
Ideally the figure should be danced in almost a straight line.
Each step has a straight travel vector - \(\vec{T}_{\text{step}}\) - defined by:
A direction travel
A magnitude (i.e.. step size)
A starting point
An end point defined by the length of stride. The end point is not usually known until travel has started and Follower has put weight on their moving foot.
The dancer going backwards always has final control over the step length since:
A dancer can put weight on their foot early to “lock in” the travel vector,
Or delay weight on their foot to adjust for balance,
The ever popular "to stop themselves falling over".
This means:
CBM depends on multiple variables:
CBM is not a "thing you do" — it's a consequence of Frame rotation.
- CBM commences with the first beat of music,
- CBM rotation continues smoothly throughout the beat — this governs both how far and how fast the step occurs.
- CBM stops when the dancer going backward puts weight on their moving foot
CBM is a rotation of the frame — not the traveling foot.
This perspective reframes how turns are taught and executed:
And in simpler terms for those that don't want to wade through the physics:y ou’re dancing forward in a straight line — that’s your momentum, or energy of movement. (That energy is called 'Kinetic Energy' (KE) or the 'energy of movement'.)
Now imagine you need to change direction.
When you change direction:
It’s like pulling a rolling suitcase:
CBM is not a sudden twist — it’s a smooth redirection of energy using your whole frame. When done correctly:
But if you try to jam it all onto the start of a beat
Please do read the:
The amount of energy your body can carry through a turn depends on the angle between the old direction and the new one:
In math terms (only if you want it):
\[ \text{Energy retained} = KE \cdot \cos^2(\theta)\]
\[ \text{Energy lost to rotation} = KE \cdot \sin^2(\theta)\]
CBM should feel like a gradual steering of energy, not a sudden wrenching twist.
🧘 Smooth rotation = smooth power
💥 Forced twist = energy loss + partner confusion
When a dancer moves with velocity along a travel vector \(\vec{T}_1\) and transitions to another travel vector \(\vec{T}_2\), the kinetic energy (KE) from \(\vec{T}_1\) )\(must be partially redirected into {\vec{T}_2}. The degree of redirection is determined by the angle\)\theta$ between the two vectors.
Let:
\[ KE_{\parallel} = KE_1 \cdot \cos^2(\theta) = \dfrac{1}{2} m v_1^2 \cos^2(\theta)\]
\[ KE_{\text{rot}} = KE_1 - KE_{\parallel} = \dfrac{1}{2} m v_1^2 (1 - \cos^2\theta) = \dfrac{1}{2} m v_1^2 \sin^2\theta\]
This rotational energy is required to reorient the body and generate angular momentum during the transition.
CBM must be thought of as a rotational redirection of momentum