The importance of heel compression in the measurement of diurnal stature variation.

Heel pad thickness was measured in 20 subjects (18 males aged 21-39 years and two females aged 21 and 25 years) using a 2 MHz ultrasound transducer linked to an Echo Scan body composition meter, Thandar SC110A oscilloscope and M150 amplifier. With the subjects standing erect and weight-bearing equally through both feet, the average time to achieve equilibrium heel compression was 81.7 s. Compression of the heel pad soft tissue averaged 4.4 mm (range 0.8-8.9 mm). Following equilibrium with one foot weight-bearing, an additional average loss of 1.6 mm of thickness (range 0-4 mm) was observed occurring after an average time period of 51 s. This study has confirmed the suspicion that heel pad shrinkage may be a confounding factor in measurements of change of stature. The results of this study have indicated that a period of 2 min is needed for the heel pad thickness to compress sufficiently before measurements are taken.