if hair has a stage where it stops growing then.....

[jojo]

how come if say you grew your hair to your ankles or wherever and it didnt grow for say 5 years, you obviously would persume you had reached terminal length yes? Well if you went and had it cut short it would grow again, well how can this be if your hair is dead and has no memory?

how does it know it has been cut and more to the point how does it know how long it has got?

Surely if hair can start growing again when its cut short, it can kick start growth if you cut just a few inches off.

hope this makes sense!

[CindyLea1]

As I see it---- At Terminal, your hair grows to there, and the shed hairs grow that long. So you shed out a hair that restarts growing from the scalp, but never gets longer than terminal.

If you cut it and it say waist, and it grows again. It is only the shed hairs that grow, any hairs that were already at terminal at the cut date, just fall out and are replaced by the sheds which grow on.

[vindo]

Easy, I see where you are confused.

Hair only grows to a certain length for a certain amount of time. Many people can easily grow to shoulder length in no time.
For something like ankle length it takes not only more time but also special genes.
Most peoples hair sheds before it reaches a significant length like that. Hair always grows...even at terminal length.
You will just not have visible length gain anymore because the hair will fall out once it reaches its max. length.
Reason you don't end up with shorter hair is because by the time you shed that long hair 5 others have grown to that length. :)
Taper can tell you something about terminal length btw. ;)

[jojo]

Thanks that makes sense but how does hair know its reached its potential longest length? is this weight of the hair or just good old genetics?

[RavennaNight]

I think terminal length is the longest your hair would be genetically inclined to grow before it naturally sheds from your head. Technically there is supposed to be a cutoff for everyone, a point where your hair can just grow no longer. All the hairs on your head are at different stages of their life and I think that is why it has to stall growth 5 years to call it terminal. Because the average of your hairs evens out I think? I hope I am making sense...

[Roseate]

Thanks that makes sense but how does hair know its reached its potential longest length? is this weight of the hair or just good old genetics?

It is a timing thing, determined by genetics. One hair will stay on your head for a predetermined amount of time, several years at least, and if you don't cut it, it will keep growing. But at the end of that time, it will shed whether you cut it or not, and the length that it can get to in that time is your terminal length.

So your hairs don't know. They grow the same amount whether you cut them or not, but at the end of the anagen phase, they shed. At terminal, they are just replaced by other hairs that are in a different growth phase; your follicles aren't all in the same phase at the same time. Wiki (http://en.wikipedia.org/wiki/Hair_follicle) actually does a decent job of explaining.

[iris]

Thanks that makes sense but how does hair know its reached its potential longest length? is this weight of the hair or just good old genetics?
The follicles work on a cycle - they'll produce hair for a few years, then rest for awhile, then the hair is shed and the cycle starts over again.

How long your hair can get, is determined by two things:
1. how long your hair-producing cycle is
2. how fast your follicle produces hair (= how fast your hair grows)

The time for which a follicle can produce hair is something like 5-7 years (I think?). There's individual variation here, - if your follicles have a long cycle, so if they produce hair for a long time before they rest, your hair can grow longer.

The other source of variation is how fast your hair grows, so how much hair the follicle produces, say per month. Some people's hair grows fast, other people's hair grows more slowly.

I wouldn't say that memory has anything to do with it, but it depends how you look at it I guess. In a way you could say follicle has to 'remember' to stop producing hair, it has to 'know' when it's reached the resting point of its cycle. How it 'knows' that it's time for a break, I don't know. I doubt anybody does, but if they do it'll be in biochemical terms that we wouldn't follow anyway :). Many processes in the body work on some kind of 'clock', for instance your heart beat is produced by a chemical reaction that has a certain rhythm to it, - it's all chemistry in the end, but how each and every process works individually, I don't know how much is known about that.

But the hair doesn't have to 'remember' how long it can grow, the follicle just keeps on producing hair until it rests. How much you cut off while it's producing hair shouldn't matter for how much hair it ends up producing.

[spidermom]

To say it in different words than Emichiee: It's not a terminal length, it is a terminal time.

Each hair has it's own growth cycle. For the sake of example, let's say that the average hair on your head grows for 60 months before it sheds out. If it grows at a rate of 1/2 inch per month, by the end of 60 months, it will be 30 inches long.

It's not that the hair "knows" it will be finished growing when it reaches 30 inches long. It's that it has reached the end of it's growth cycle.

Once a hair stops growing, it does not begin growing again. If you cut 12 inches off that hair, it will still shed out after a few months.

However, other hairs will be newer. It is those hairs that will grow out to 30 inches long, not the one that had reached the end of its cycle and therefore its longest length.

Actually, each hair can have its own growth cycle. While that one grows for 60 months at 1/2 inch per year, there will be other hairs on your head that grow 3/4 inch per month for 10 months, others that grow 1 inch per month for 80 months. That is why some of the people who have grown for a very long time without trimming their hair can have a lot of taper. Sometimes they only have 50 hairs on their head that grow for a long time at a fast rate, so of course that longest layer won't be very thick.

I hope I've contributed something valuable to the discussion. I see that others were posting while I was thinking and typing (and correcting typos), so everything has been said just about every way there is to say it.

[Merewen]

It might help to think of an individual hair strand. A single hair strand grows a certain amount of time before it stops and falls out.
The length that hairs will get before they fall out is terminal length.

The other thing is that hairs are all at varying points in the growth cycle. They don't all start growing at the same time; they don't all fall out at the same time (thank goodness!). So when you cut your hair from terminal length, the hairs that have not grow their terminal period of time will continue growing until they hit the end of the cycle. Thus the hair will seem to grow as a unit.

[vindo]

Yup its good to think individual hairs, thats what I have going on...some make it to classic length but not too many. When maintaing I might be able to improve that because some others get a chance to keep up...
I feel I do have many hairs that shed somewhere around waist-tb.

[ilovelonghair]

Terminal lenght can be different depending on age, for example my had something weird going on: terminal lenght was shorter when she was in her 20's than it was after she reached her 30s. After 30's it could grow really long (she kept cutting it so it never reached terminal). I have no idea why that is, but I suspect this happens to more people. My hair also got better over time.

[rogue_psyche]

I understand the basic idea of terminal length, but I just thought of a question. What about when you shed (not break) a hair prematurely due to rough handling? Does that start the terminal timer over, or does the countdown to shedding stay where it was pre-shed?

[eadwine]

How about thinking about individual follicles? Even easier. The length of the hair is not even a factor.

A follicle produces hair for an x amount of time at an x amount of growth rate, those two numbers are all about genetics. When the follicle has reached that x amount of time of producing a hair it sheds it and starts a new hair.

So you can cut that hair, break it off, or not.. it won't matter. Time is up, and off it goes.

[jojo]

To say it in different words than Emichiee: It's not a terminal length, it is a terminal time.

Each hair has it's own growth cycle. For the sake of example, let's say that the average hair on your head grows for 60 months before it sheds out. If it grows at a rate of 1/2 inch per month, by the end of 60 months, it will be 30 inches long.

It's not that the hair "knows" it will be finished growing when it reaches 30 inches long. It's that it has reached the end of it's growth cycle.

Once a hair stops growing, it does not begin growing again. If you cut 12 inches off that hair, it will still shed out after a few months.

However, other hairs will be newer. It is those hairs that will grow out to 30 inches long, not the one that had reached the end of its cycle and therefore its longest length.

Actually, each hair can have its own growth cycle. While that one grows for 60 months at 1/2 inch per year, there will be other hairs on your head that grow 3/4 inch per month for 10 months, others that grow 1 inch per month for 80 months. That is why some of the people who have grown for a very long time without trimming their hair can have a lot of taper. Sometimes they only have 50 hairs on their head that grow for a long time at a fast rate, so of course that longest layer won't be very thick.

I hope I've contributed something valuable to the discussion. I see that others were posting while I was thinking and typing (and correcting typos), so everything has been said just about every way there is to say it.

Ah now that makes sense, terminal time is a more acurate way of putting it! Cor complicated stuff though eh!

[jojo]

Thanks everybody for your input, its basically a cycle which length has no say in!

[eadwine]

Exactly right! :)

[spidermom]

I understand the basic idea of terminal length, but I just thought of a question. What about when you shed (not break) a hair prematurely due to rough handling? Does that start the terminal timer over, or does the countdown to shedding stay where it was pre-shed?

Sometimes if you pull out a hair before it is ready to shed, the follicle is damaged and a new hair never grows from that follicle again. But most of the time the follicle isn't damaged and a new hair will grow from it eventually.

I've heard also that there's a limited number of cycles that each follicle goes through, then it's done and grows no more hair. That is why elderly people can have quite thin hair. This, like everything else about hair, varies. Some follicles might go through only 5 cycles, others will have 10 or 12 or even more.

[windinherhair]

This thread is really interesting! I have been wanting to ask a similar question so now everything is answered. Thanks! :)

[beachwaves]

Very imformative! I wonder what my terminal length will be. I have had it to tailbone before so I know it will get that long...maybe longer!

[beachwaves]

Terminal lenght can be different depending on age, for example my had something weird going on: terminal lenght was shorter when she was in her 20's than it was after she reached her 30s. After 30's it could grow really long (she kept cutting it so it never reached terminal). I have no idea why that is, but I suspect this happens to more people. My hair also got better over time.

It seems this is the same with texture too. Mine has gotten curlier as I get older.

[ilovelonghair]

Same for me, mine used to be so straight, and now I even can have some very slight spirals (with LOTS of aloe only)

[nowxisxforever]

Thanks that makes sense but how does hair know its reached its potential longest length? is this weight of the hair or just good old genetics?

It doesn't know... it merely grows.
Each follicle has a growth cycle which dictates what your terminal length is. Say for example a growth cycle with ~6 years, your hair will grow its normal rate for 6 years, then the hair will fall out and a new one will grow.

It has nothing to do with physical length and everything to do with the growth cycle of the individual hair.

Which is why people with awesome hair genes can grow to lengths past what the rest of us can... their growth cycle is much loooonger, letting their hair grow longer before it falls out.

[nowxisxforever]

Thanks everybody for your input, its basically a cycle which length has no say in!

I guess I was too late! But yep pretty much! :]

[longinthehair]

Oh shoot! Looking at this thread, I guess I might have cut off my five or so potentially longest & fastest-growing soon-to-be (but who knows?) terminal hairs w. a small micro-trim the other day! Yikes! I feel sick..
Kidding.. But it is a bit mind-boggling when you really think about the process of each hair individually growing and what stage each one may be at! (Thank goodness they're not all at the same stage.) I think I'm having an autumn shed going on, and if they were all at the same growth stage, I'd probably be bald right now..