I have tried the McKenzie Chin Tuck posture and it absolutely makes you measure taller but your eye level appears shorter. It is not a breakthrough by any means but I have tried and you can see yourself becoming taller in the mirror when you do it.

So when you adopt this posture you measure taller because you are maximizing the apex bump of your head. But personally, I feel shorter because with a more backwards head posture my eyes are at a higher level so people are shorter relative to high level.

There is an exercise related to this where you push the chin back to get a neck muscle stretch and there are some indications that it may be worthwhile to do this.

I write more in my response to Body Height changes with hyperextension. Basically temporary hyperextension of the spine(15s) can result in temporary height gain due to disc hydration. And I think this exercise may achieve hyperextension of disc components. So I’d say it’s worth doing but only brief periods as you would be better suited to strengthening your neck muscles via something like free weight training or machines if you can’t do free weights due to injury or a structural reason.

It’s mentioned further in the body height changes with hyperextension study that it’s putting the load on the facets that enables for disc hydration. You’d think that tilting your head back would actually put the load on the facets. But I think the key is that tucking your chin in achieves neck muscle activation and if you look at the back muscle anatomy if the muscles are activated they will pull everything upwards.

Note that the majority of the back muscles slope upwards so when they are contracted they indirectly pull up the spine in alignment. I write about the muscular pull maximizing height gain here.

So I’d say in general adopt the mckenzie chin tuck along with chest up/shoulders back to maximize back muscle activation in posture. And occasionally do the press the finger against the chin thing for short periods of time to allow for disc hydration.

The drawback for the mckenzie chin tuck posture is that although it makes you measure taller it makes your jaw look smaller.

Here’s a video that explains it more:

I find that just bringing your chin is enough to get a good height gain appearance without having to worry about protecting the technique yes as mentioned you will have double chins but you will measure taller.

This guy looks taller after doing the McKenzie chin tuck:

Here’s a study that backs up the McKenzie chin tuck:

Head posture and loading of the cervical spine

” Precision stadiometer tests were run, using seven subjects, to measure the effects on spinal length of different angles of gaze. After 1 h exposure whilst sitting in a controlled posture, there were significant differences in the shrinkage of the spine between the horizontal gaze and the 20° and 40° angles below the horizontal. The increased spinal loading demonstrated by the increase in spinal shrinkage calls into question the recommendations for angle of gaze recommended in textbooks.”

I think it is the forward posture affecting the height change and not actually the gaze of the eyes.

“The mean compressive load on the cervical discs was 10 kg higher for the forward flexed position”

“Each subject would attend on three separate days, on each of which one of the three
randomly chosen head angles, 0 degree, 20 degrees and 40 degrees, would be tested.”

“A shrinkage of the spine during the forward inclination of the head, observed during this
experiment, of approximately 1 mm over a 1 h period, equivalent to about 5% of the total diurnal shrinkage”