Protocol variations in arm position influence the magnitude of waist girth.

Waist girth is recognised as a better predictor of obesity, particularly abdominal obesity, compared to other measures. Although several protocols for waist girth exist, arm position is either ignored, or not specified in unambiguous terms. Therefore, the purpose of this study was to determine if arm position influenced anthropometric waist girth measurement. Waist girth was measured in 92 adults (19 males, 73 females) with arms relaxed, abducted, horizontal, folded across the chest (three variations) and raised vertically. Duplicate measures, in all positions, were recorded by a single International Society for the Advancement of Kinanthropometry (ISAK)-trained technician to a precision of 0.2% technical error of measurement (TEM). Arm position had a significant effect (P < 0.001) on waist girth. Male participants had greater waist girth than females (P < 0.001) and the waist girth differences across the varying arm positions exhibited a significant position-by-gender interaction (P < 0.001). The arm position-by-body mass index (BMI) category interaction was also significant (P = 0.016) with greater differences observed at higher BMI. These findings suggest caution in comparing results of different studies where arm position is not specified and indicate that the arm position corresponding to the ISAK protocol has the lowest error and is therefore recommended.