The Hair Growth Phases

Hair growth phases or stages
Q: I've been trying to grow my hair out for a long, long time. I get it trimmed regularly to keep it healthy and remove split ends, but it seems like I've reached a "dead end" as far as gaining any more length. Am I doing something wrong, or do I just need to keep letting it go (and letting it grow)?
A: The maximum length to which you can grow your hair is basically a matter of genetics. Some people can grow thick, lustrous tresses that tickle their toes (like 70's country music star, Crystal Gayle), while still others find that getting their hair to grow past their shoulders is a Herculean task.
Human hair cycles through three stages:
The anagen phase or growth phase is when all new hair growth occurs. During the anagen phase, hair grows at its normal rate (an average of half an inch per month), and 90% of the hairs on your head will be in the anagen phase at any given time. Each specific hair can be in the anagen phase for an average of three to five years, but it can last as long as ten years in some cases.
The catagen phase, a transitional phase that follows the anagen phase, signaling the end of the growth phase. During the catagen phase, the hair follicle contracts and detaches from the dermal papilla (where it gets its nutrients). The hair bulb disappears, and the root end of the hair forms a rounded club. Less than 1% of the hair will be in the catagen phase at any given time, and this phase usually lasts one to two weeks.
The telogen phase is also known as the resting phase and is the last phase in the hair's growth cycle. The telogen phase lasts until the fully grown hair is shed. Hair that is in the telogen phase is usually shed during this phase, or after the start of the next anagen phase when it gets pushed out of the follicle.
The hair growth cycle
10% of the hair of your head will be in the telogen phase, which can last from three to six months, usually. Once the telogen phase ends, the anagen phase of that follicle begins again. The whole cycle of hair growth - all three stages - repeat on an average of every four to five years.
This means that if your hair averages a four-year anagen phase, and you have your hair trimmed one-half inch every three months, you can expect your hair to grow four inches each year, or a total of sixteen inches before it reaches the catagen phase. The hair can appear considerably shorter if it has more than a minimum of waves or curl. Your head size, shape and your height all can make your hair appear shorter by comparison to someone else whose hair length measures identical to your own.
If you've been trying to grow your hair out for more than five years, you may have to consider that your hair just isn't predisposed to grow as long as you'd hoped. Otherwise be patient for a while longer and see if you can't get a few inches more.
Images: Designua & Alila Medical Media/Shutterstock
See also:
The speed of hair growth
What is hair made of and how does it grow?
Hair diseases