Optimal Span between Feet of Public Squat Toilet Based on Anthropometric Data and Squatting Stability Assessment

Sitting toilets are preferred globally because they afford a relatively comfortable posture. However, squat toilets are among the most common toilets in numerous public areas because of their advantages, including personal hygiene, easy cleaning, and health benefits. This study attempted to determine optimal toilet design parameters and recruited 50 Taiwanese and 50 Southeast Asian women and collected span between feet (SBF) data for participants squatting in their most comfortable posture, and also surveyed maximum outer width (MOW) data of 28 public squat toilets in Taipei. Finally, we compared the squatting stability levels of 40 female participants (20 Taiwanese and 20 Southeast Asians) who squatted for 2 min at comfortable SBF and MOW-based SBF values. The results revealed that the minimum and maximum SBFs of Taiwanese were 14.52 cm and 18.40 cm, and that of Southeast Asians were 15.64 cm and 20.40 cm, respectively. No significant difference was observed in the SBFs between the two groups was observed. The mean (range) MOW of the surveyed toilets was 27.7 (27–29) cm. Analysis of variance results showed no difference in stability between the two SBFs. This implies that the comfortable SBF (i.e., 16 cm between the participants’ heels) was narrower than the MOW, as commonly used, indicating that the comfortable SBF can be considered as an optimal toilet width parameter because of its constant stability.