thecel
narrow-orbits brachy-skull ogre
- Joined
- May 16, 2020
- Posts
- 23,166
- Reputation
- 47,908
Introduction to the Downswing Ratio
The downswing ratio is the difference between one's actual midface ratio (MFR) and their predicted midface ratio based on typical growth from infant to adult. Positive values indicate downward growth, and negative values indicate a more compact than usual midface.
Downswing ratio = (reference adult MFR) ÷ (reference infant MFR) × (MFR of the subject as a baby) − (the subject's current MFR)
The reference ratios should be measured from facial composites of people of the same gender and ethnicity as the subject. However, since it's hard to find composite images of infant faces, measuring from several photos of babies and taking the average is also acceptable. If you're lazy like me, you can just use a single sample.
The Downswing Ratio in Action (Case Study)
To demonstrate the application of the downswing ratio, we'll use a guy who has a very long midface as well as a very short IPD—me.
My midface ratio is 0.825.
When I was a baby, my midface ratio was 1.105.
For the reference ratios, I measured the midface ratios of this illustration of a generic adult and an infant:
The adult's midface ratio is 1.039, and the baby's midface ratio is 1.343.
Let's plug the numbers into the downswing ratio formula and see what comes out:
1.039 ÷ 1.343 × 1.105 − 0.825 = 0.02987
My downswing ratio is approximately +0.03, which means my midface ratio is about 0.03 lower than expected based on the typical midface lengthening factor from infant to adult.
Uses of the Downswing Ratio
A use of the downswing ratio is to calculate a very rough estimate of how much shorter one's midface could've been if they had mewed.
If we use the formula without subtracting the subject's current MFR, we get the subject's expected midface ratio, a.k.a. their "genetic potential."
Genetic potential MFR = (reference adult MFR) ÷ (reference infant MFR) × (MFR of the subject as a baby)
Here's mine:
1.039 ÷ 1.343 × 1.105 = 0.85487
0.85 is still a bad MFR.
From this number we can calculate (again a very rough estimate that's by no means scientifically accurate) the amount of excess midface length they have in absolute units such as millimeters.
X = distance to genetic potential in mm = (current IPD in mm) ÷ (current MFR) − (current IPD in mm) ÷ (genetic potential MFR)
A positive result from this formula means the subject's midface is X mm longer than its genetic potential, and a negative result means the midface is X mm shorter than its genetic potential.
Here's mine:
56 mm ÷ 0.825 − 56 mm ÷ 0.85487 = 2.37175 mm
Yeah, so if I had mewed and not mouth-breathed, my midface ratio would be only 2.4 mm shorter than it is now. That's barely anything!
The key takeaway from this case study: I'm genetically doomed from the beginning, and mewing couldn't've saved me.
The downswing ratio is the difference between one's actual midface ratio (MFR) and their predicted midface ratio based on typical growth from infant to adult. Positive values indicate downward growth, and negative values indicate a more compact than usual midface.
Downswing ratio = (reference adult MFR) ÷ (reference infant MFR) × (MFR of the subject as a baby) − (the subject's current MFR)
The reference ratios should be measured from facial composites of people of the same gender and ethnicity as the subject. However, since it's hard to find composite images of infant faces, measuring from several photos of babies and taking the average is also acceptable. If you're lazy like me, you can just use a single sample.
The Downswing Ratio in Action (Case Study)
To demonstrate the application of the downswing ratio, we'll use a guy who has a very long midface as well as a very short IPD—me.
My midface ratio is 0.825.
When I was a baby, my midface ratio was 1.105.
For the reference ratios, I measured the midface ratios of this illustration of a generic adult and an infant:
The adult's midface ratio is 1.039, and the baby's midface ratio is 1.343.
Let's plug the numbers into the downswing ratio formula and see what comes out:
1.039 ÷ 1.343 × 1.105 − 0.825 = 0.02987
My downswing ratio is approximately +0.03, which means my midface ratio is about 0.03 lower than expected based on the typical midface lengthening factor from infant to adult.
Uses of the Downswing Ratio
A use of the downswing ratio is to calculate a very rough estimate of how much shorter one's midface could've been if they had mewed.
If we use the formula without subtracting the subject's current MFR, we get the subject's expected midface ratio, a.k.a. their "genetic potential."
Genetic potential MFR = (reference adult MFR) ÷ (reference infant MFR) × (MFR of the subject as a baby)
Here's mine:
1.039 ÷ 1.343 × 1.105 = 0.85487
0.85 is still a bad MFR.
From this number we can calculate (again a very rough estimate that's by no means scientifically accurate) the amount of excess midface length they have in absolute units such as millimeters.
X = distance to genetic potential in mm = (current IPD in mm) ÷ (current MFR) − (current IPD in mm) ÷ (genetic potential MFR)
A positive result from this formula means the subject's midface is X mm longer than its genetic potential, and a negative result means the midface is X mm shorter than its genetic potential.
Here's mine:
56 mm ÷ 0.825 − 56 mm ÷ 0.85487 = 2.37175 mm
Yeah, so if I had mewed and not mouth-breathed, my midface ratio would be only 2.4 mm shorter than it is now. That's barely anything!
The key takeaway from this case study: I'm genetically doomed from the beginning, and mewing couldn't've saved me.
Last edited:
