Diurnal variation in stature and sitting height in 12-14-year-old boys.

1. Measurements of stature and sitting height were made at 0930 and 1400 h on 19 boys aged 12-14 years with the "stretching upward" technique. 11 different boys were similarly measured at 1000 and 1700 h. 2. The average decrease in stature from 0930 to 1400 h was 2.0 mm and from 1000 to 1700 h was 4.6 mm. The corresponding values for sitting height were 2.0 mm and 2.8 mm. 3. No strong evidence for individual differences in diurnal change was found. 4. The standard error of stature measurement, estimated from duplicate measurements taken five minutes apart by the same observer in the afternoon sessions, was +/- 1.8 mm.