Postural and spinal stability analysis for different floor sitting styles

Abstract

In contrast to Western countries, traditional floor-seating cultures are prevalent in Korea, Japan, the Middle East, and Africa, where sitting on the floor in static positions such as squatting, kneeling, or sitting cross-legged is common. Most studies on sitting posture have predominantly focused on chair sitting in Western cultures, resulting in a cultural bias. This study aimed to investigate the effects of different cushion types (floor and traditional cushions of 3-cm, 5-cm, and 8-cm thickness) and seating postures (cross-legged, mother's leg, and kneeling) on measures of postural stability, trunk muscle activity, rotational spinal stability, and subjective postural stability in an Asian population. Forty right-hand and right-foot-dominant volunteers who did not experience activity-limiting back pain in the past 12 months were recruited. Multivariate analyses of variance (MANOVA) and ANOVA with a repeated-measures design were employed to assess the within-subject effects of the cushion type and seating posture. An alpha value of 0.05 was set for statistical significance. The results of this study suggest that preventing lordosis posture, seating on the floor, and maintaining a kneeling posture may reduce the loss of balance and trunk muscle fatigue. These results emphasize the need for additional ergonomic studies that focus on the seating traditions of Asian cultures.

Keywords: Floor seating; Postural stability; Seating postures; Trunk muscle activity.

Fig. 1

Experimental Equipment × Foams (Density: 33.5 kg/m², Hardness: 7.2 kg/314 cm², Tear strength: 0.6 kg/m², Tensile strength: 1.0 kg/cm², Elongation: 110 %, Rebound: 5 %), Test method (KSM 6672, JIS 6401).

Fig. 2

Definition of the seating and spinal postures.

Fig. 3

Experimental scene.

Fig. 4

Definition and calculation of COP with L-R and A-P.

Fig. 5

Descriptive statistics of the measures of center of pressure; distance for the seated posture depending on the type of cushion, seated posture, and spinal posture.

Fig. 6

Interaction effect of curvature and posture on the anterior and posterior (**: p < 0.05, ***: p < 0.01).

Fig. 7

Main effect cushion (a) and interaction effect of posture and curvature (b) on subjective discomfort (**: p < 0.05, ***: p < 0.01).

Fig. 8

Significantly different normalized EMG of cushion, seated posture, and spinal posture (**: p < 0.05, ***: p < 0.01).

Fig. 9

Descriptive statistics for the measures of stiffness: sagittal, coronal, and transverse.

Fig. 10

Main effects of spinal posture, cushion, and seated posture on rotational spinal (a) sagittal stiffness, (b) coronal stiffness, and (c) transverse stiffness (**: p < 0.05, ***: p < 0.01).