Why your shirt gets pulled out
Updated: Mar 25
Have you ever wondered why your shirt gets untucked? Probably not. It is one of those things that normal people do not exactly think about. I, on the other hand, am a big nerd and I think it is still interesting to understand how it happens in order to avoid it. We will see that it is hard, or should I say, impossible to fully get rid of the Curse, even with a bespoke shirt. The latter certainly helps - a lot - but doesn’t change how your shirt works.
Let’s go directly to the heart of the problem: the pulling force applied by our arms as we move them throughout the day. As we grab something, raise our arms up, move them in front or behind, we are exercising a force that lifts the fabric of our shirt and pull it from our belt. Afterwards, as we lower our arms to a rest position, that fabric previously lifted will not get back under our belt without another pulling force from below. These very simple mechanics result in the muffin top.
The effect of that phenomenon is worsened as your shirt inadequately fits you. That can be explained by the length of the fabric between the armpits and the belt. It is not expandable as with stretching fabrics so the fabric can only be displaced once fully extended. Accordingly, the shorter that length, the likelier the fabric gets pulled out from your trousers when your arms are raised. Only in the case where the fabric perfectly fits the contours of your arm that the pulling force will draw no or little extra fabric from the waist.
We would tend to believe that the solution is to wear tight-as-possible shirts in order to diminish the pulling effect. And it is true that better fitted shirts dramatically improve its wearer overall look. Yet, it is far from being enough. The main issue is that, contrary to what the illustration above may lead to believe, the pulling effect does not apply to one stitch only but on multiple spots over an armhole, each of them more of less required depending on the movement. So, unless your shirt perfectly fit your armpit - which is impossible unless you’re wearing a jumpsuit -, some movements will always pull your shirt from your trousers.
The illustrations below demonstrate that multiple pulling effect using a shirt stay belt and a regular t-shirt. The stretching t-shirt highlight which part of it is being pulled by my arms as I move them. I consider the test t-shirt as a close fit already, more than any of my shirts. But, judging by the lines of tensions from the pictures below, it’s not enough.
You may have noticed that your shirt tended to come off easier when you sat down. It is because your pants are another reason why your shirt gets untucked. As you take a sitting stand, your knees pull the fabric from the thigh area of your pants forward, creating a pulling stress on several spots. These strains are particularly visible with fitted pants as shown in the following picture.
The pulling force applies both on the interior and the exterior side of the pants. The pulling force on the exterior stretches the buttock area, which explains why that part is generally flat in a sitting stand. It is similar to stretching the sheets on the edges of the bed to smooth out the center. The pulling force on the inside pulls the crotch area. The result at the opposite end of that area is… a whale tail.
The consequence of all that on the shirt is that the waist area of the pants, being pulled, also pulls the bottom of the shirt because of friction between fabrics. Thus, through friction, the pulling force exerted by the knee in a sitting position will also pull the shirt down, and often stretch it.
Without further movement, the effect on the shirt should not be significant because it just returns to its original shape when the pulling force stops, i.e., when you get back up. You can test this hypothesis by performing a squat with your hands and arms at rest. You will feel the back of your shirt quickly getting tense in the squatting position, but it takes back its usual length when standing.
However, in a sitting position, no one has their hands perfectly down. In general, on the contrary, our arms tend to have a naturally high position and movements. We grab a file on the corner of the desk, we type something on the keyboard, we scratch our heads in front of our laptop. Thus, the shirt that has already been stretched by the sitting position (pulling force downward), will undergo another pulling force from your arms (pulling force upwards). That extra pulling on an already stretched shirt will dislodge it from the pants - which only exerted friction to retain it. Hence, a muffin top once back in a standing position.
You may now ask yourself now: what was that for? What useful knowledge would I get from this analysis? And here are my conclusions:
No amount of bespoke will ever entirely solve the issue with both pulling forces, especially in an era where close-fitting outfits are the ongoing trend. So many spots on the armhole are subject to a pulling effect as you move. If a bespoke shirt can reduce the effect and the visual results, it will never perfectly marry the contours of your arms. So, if you plan to buy one for the sole aim of avoiding a muffin top, it won’t work perfectly. And you will still have to tuck your shirt occasionally, but certainly will less frequency. Of course, there are many other - and better - reasons to be tempted by a bespoke shirt.
For the same reason, devices or trick which sole purpose is to increase the friction exerted by your belt to the bottom of your shirt, for example, by adding sticky parts, or by fixing some part of the shirt with the pants or the underwear, will always have a limited effectiveness. They may work to a certain extent, but not under more vigorous circumstances. And if they are effective, let’s say you decided to pin your shirt onto your underwear, the result is that both pulling forces will be exercised permanently. In other words, your knee will constantly push your pants down, and your arms will constantly push your shirt up. Such a situation is unenviable because it ultimately creates discomfort that will be felt more and more, as the hours flies. In the worst-case scenario, your underwear, being pulled up with your shirt, will just squash your family jewels.
The ultimate observation I would point out is that, as a consequence of the previous result, the most effective devices requires a force that pull your shirt back into your trousers. Accordingly, if you’re hesitating between shirt stays devices at the moment, I would recommend focusing your research on classic shirt stays and shirt garters.
Of course, for the sake of science, James and I will still try them all!