Arm span
Arm span or reach is the physical measurement of the length from one end of an individual's arms to the other when raised parallel to the ground at shoulder height at a 90° angle. The arm span measurement is usually very close to the person's height. Age, sex, and ethnicity have to be taken into account to best predict height from arm span. Arm span is sometimes used when a height measurement is needed but the individual cannot stand on a traditional stadiometer or against a wall due to abnormalities of the back or legs, such as scoliosis, osteoporosis, amputations, or those who are confined to a bed or use a wheelchair. Other, possibly more accurate measuring techniques include knee length or recumbent length when possible.
Because any decrease in height will cause an increase in the ratio of arm span to height, a large span to height ratio may sometimes be an indicator of a health problem that caused a vertical height loss such as postural changes due to ageing or any spinal conditions such as degenerative disc disease.
Arm span in sports
An above-average reach may be advantageous in sports such as Australian rules football, basketball, tennis, boxing, mixed martial arts, volleyball, discus throw, fencing, rock climbing, and swimming. For instance, boxer Sonny Liston, while 185 cm tall, had a reach of 213 cm. Another example is former UFC Heavyweight and Light Heavyweight Champion Jon Jones, who is 193 cm tall, but has an advantageous reach of 215 cm.This unusually long reach has allowed them to hit from relatively safe distances where opposing fighters cannot hit back. However, a long arm span is mechanically disadvantageous on the bench press.