It’s not about length, it’s about TIME.
Now, there’s a very important point to be made. You often hear people say “Well, my hair grows to (insert length here) and stops, so this must be my terminal length and genetics. This is not completely true. ” Your particular hair length does not determine when your hair stops growing or goes into resting (telogen) phase. TIME does. Our hair doesn’t stop growing at a certain length-it stops growing after a certain time period. Again, this is where genetics comes in. This time period, or growth phase, is set by genetics with the average growth phase for hair on the head being 2-6 years for humans across racial lines. Some of us have longer phases, some have less. And, this is where the terminal length argument can get tricky. While terminal hair length is determined by the amount of time a hair has been growing overall, the argument logically follows that if left to grow undisturbed (no breakage/cutting), terminal length does eventually translate into a particular length of hair. Unfortunately, many of us have not been growing our hair long enough under very healthy hair conditions to see our strands reach and be maintained at our true terminal lengths for any given period of time. Some of us have old, beat up hair from our pre-hair care days that will need to shed and pass on before our hair stands a chance of reaching within the bounds of our terminal hair length. Others of us prefer neat hemlines to our ends and length, and so the regular trimming and touching up will prevent us from seeing our full length potential.
I am willing to go out there with almost 99.9% certainty and say that shoulderlength and APL (armpit/arm crease length) are hardly anyone’s terminal lengths. If growth cycles range from 2-6 years, then the woman with the shortest growth cycle of two years can expect her hair to reach 12 inches in length before the hair will shed- assuming she has not trimmed or lost any length to breakage. Thanks to the spherical shape of the head, for many of us, 12 inches measured from the nape and ear area on down will equal at least brastrap length. For women with longer growth cycles, waist length and longer lengths are not uncommon terminal lengths. Most experts agree that a terminal length of between 1 and 3 feet is typical.
Is Terminal Length a Real Concept?
You often hear arguments about whether or not terminal length actually exists. It does! All hair on your body is subject to predetermined genetic growth and resting phases. Your eyelashes, arm, and leg hairs go into a resting phase within a few months after the onset of growth. This is why this hair doesn’t get very long whether you shave it or not. Just like the hair on your head, the hair follicles on your arms and legs do not go into resting phase as soon as the hair hits a certain length. They go into resting phase when their growing time frame has expired- which may correlate with a certain length when experienced over time. Without terminal hair lengths, and some type of order to our growth, we’d be braiding our arm and leg hair.
To sum it up– if your growth cycle happens to be 4 years for your head hair, no matter how long your hair is at that point it is going to be shed at that 4 year mark. You could either have gained as much length as your growth rate will allow you to gain within that 4 year time period… or you could shave it bald at 3 years and 355 days in and it will still shed at that same 4 year expiration date. Your job is to make the most of your 2-6 year growth phase! Obviously, things like age, poor health, and bad hair care practices can cause hair breakage or growth cycles to shorten in length.
Audrey Sivasothy is a Houston-based freelance writer, health scientist and author of The Science of Black Hair: A Comprehensive Guide to Textured Hair Care (available on Amazon.com & Barnes&Noble.com).