Five Pulse Movements in One Breath, Qi Traveling Six Cun: Turning Qi Transformation into Numbers

One of the most important sentences to study repeatedly in the Mirror Classic of Bian Que is:

In one exhalation a person’s pulse moves twice and qi travels three cun; in one inhalation the pulse likewise moves twice and qi travels three cun. When exhalation and inhalation settle, the pulse has moved five times and qi has traveled six cun; this is called a normal person.

If this is treated merely as an ancient pulse mnemonic, its real function is missed. The passage establishes the book’s first quantitative relation.

Three phenomena are tied to the same cycle

Within one baseline breath, the text specifies:

• exhalation: two pulse movements, qi travels three cun;
• inhalation: two pulse movements, qi travels three cun;
• including the movement at the settling of the breath: five movements in the full breath;
• one complete respiratory cycle: qi travels six cun.

So this is not a standalone description of pulse rate or breathing. It says how breathing, pulse movement, and qi travel should correspond within the same span of time.

Once this relation is established, many later comparisons become possible.

If the respiratory cycle remains the same but the number of pulse movements increases or decreases, a rhythmic difference appears. If the distance associated with each movement becomes shorter or longer, the text can speak of “rapid breath and short” or “gradual breath and long.” If different channels have different lü measures, they can still be compared against the same baseline.

Six cun is not an isolated number

The text immediately continues:

When qi travels six cun in one breath of a normal person, the pulse path is Huangzhong; this is the measure by which Ying and Wei proceed.

Thus the six-cun baseline is next named Huangzhong, the reference lü. The Twelve Lü are not suddenly imported into medicine from music theory; they inherit a pulse-and-breath scale that has already been established.

The reading order is crucial:

baseline breath → six-cun reference → name this reference Huangzhong → use other lü to compare other scales of qi movement.

Reversing the order and beginning with the musical pitch of Huangzhong obscures the medical line of reasoning.

Where does “one cun and five fen per movement” come from?

During the basic exhalation and inhalation, two movements correspond to three cun. The text later directly states another baseline:

In the breath of a normal person, with one pulse movement qi travels one cun and five fen.

Three cun divided by two movements is exactly one cun and five fen per movement. The two passages are therefore internally consistent as a proportional relation.

How the fifth movement at the settling of the breath fits the rhythm of the full cycle is developed later through Hou positions, the great breath, and different respiratory structures. For now, the important point is that the text gives not just numbers but proportions.

How should these numbers be viewed today?

The most cautious approach is to treat them as the Mirror Classic’s own physiological baseline model. Whether they correspond directly to modern blood-flow velocity, pulse-wave velocity, or another physical quantity requires separate experiment and cannot be concluded from verbal resemblance alone.

One thing is clear, however: the author does not intend “qi movement” to be pure metaphor. It is constrained jointly by pulse events and proportional body measure.

The real significance of six cun, then, is not merely the number. It expresses a principle: to speak of deviation, first establish a baseline; to establish a baseline, define both time and distance.

The next article addresses the most easily misunderstood part of that distance unit: does “cun” mean a fixed number of modern centimeters?