The Correlation Between Arm Length & Leg Length

The correlation between arm length and leg length is difficult to quantify because different ethnic groups have unique body proportions. For example, Australian aborigines have relatively long legs for their height -- often longer than their upper bodies. Few studies have compared arm length to leg length. More research has been conducted on the correlation between arm span, which includes chest diameter, and height. This is because arm span is a good estimator of height in situations where height cannot easily be measured, but ethnicity also plays a confounding role in these situations.

Correlation in Adults

A study in the “American Journal of Anatomy” published in 1973 contains data useful in determining the correlation between arm length and leg length. Caucasians living near Birmingham, England and immigrants to the UK from Africa and Hong Kong were measured. The study showed that the correlation between arm and leg length for Caucasians was 1.2 millimeters of leg length for every 1 millimeter of arm length. African immigrants to the UK had 3.4 millimeters of leg length for every millimeter of arm length, and immigrants from Hong Kong had 0.77 millimeters of leg length for each millimeter of arm length. The subjects of the study were not randomly selected, but instead were patients who were measured at health clinics.

Correlation in Children

The correlation between arm and leg length in children varies greatly. A study published in the “Annals of Human Biology” showed that among Korean children in the same age group, taller children had proportionally longer legs than arm span when compared to shorter children. This suggests that there is no precise correlation between arm and leg length that applies to children even across a certain age group.

Arm Span and Height

A related subject is the correlation of arm span to height. A person's arm-span measurement can often be directly substituted for height, as these values should be similar. This is useful in respiratory therapy, where the height of the patient is used to predict how much a patient should be able to inhale and exhale. If the patient has scoliosis or bilateral leg amputations, his arm span can be used instead. Just as the correlation between leg and arm length is impacted by ethnicity, so is the correlation between arm span and height.

Uses

The correlation between arm length and leg length is of interest to anatomists, anthropologists and others who study human allometry, the science of describing human growth rates and proportions. It has immediate applications in health care, forensics and other professional fields. Ethnicity and age must be taken into account to use the correlation between arm length and leg length effectively.