Human Height
From Halbeeg, the open encyclopedia · Af-Soomaali
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Human height is the distance measured vertically between the feet and the top of the head when a person stands erect. It is typically measured in centimeters or inches using an instrument called a stadiometer, which consists of a vertical ruler with a horizontal headpiece. Height is one of the basic measurements in anthropometry (the science of measuring the human body).
A person's height is determined by the interaction of genetics and environmental factors, particularly nutrition and childhood health. For this reason, average height in a population is used as an indicator of that population's standard of living and health services, not merely as a genetic trait.
How to measure
Standard measurement is performed with the person barefoot, feet together, back and head against the measuring rod. A person's height varies throughout the day: it is greater in the morning than at night, because daytime weight compresses the cartilage discs between the vertebrae. Infants and very young children unable to stand upright are measured lying down, a measurement called supine length.
Factors affecting height
Genetics accounts for the largest portion of height variation within a uniform population. However, when comparing different populations or the same population at different periods, nutrition, childhood disease, and economic conditions have substantial effects. Hormones, particularly growth hormone and thyroid hormones, directly regulate bone growth.
Growth and age
Growth is fastest during the first year of life and then proceeds steadily until adolescence. During adolescence, a period of rapid height gain occurs called the growth spurt. Afterward, the growth plates in bones close and height growth ceases. Generally, girls reach the growth spurt earlier than boys, but boys continue growing for longer, which results in average adult male height exceeding that of females.
Height decline in older age
As a person ages, height may decrease. Causes include fluid loss and compression in the spinal discs, and bone loss (osteoporosis) which can cause the spine to curve. This change is normal, but its degree varies among individuals.