Table 4.

Kinematic variables

Scenario	Variable	Description
Trunk forward/backward
S1	$\mathrm{\Delta }{H}^t$	Observed changes in patient’s head position, detect through patient’s head area, $H^t$ ($t>1$)
S2 and S3	$a^t(p_8^1,p_1^1,p_1^t)$ $\wedge$ $\mathrm{\Delta }{x}^t(p_1^t,p_1^1)$	Spine angular and linear displacements
Trunk rotation
S1	$a^t(p_2^1,p_1^1,p_2^t)$ $\wedge$ $a^t(p_5^1,p_1^1,p_5^t)$	Simultaneous angular displacements of both shoulders
S2	$\mathrm{\Delta }{x}^t(p_{2/5}^t,p_1^t)$	Shoulder displacement regarding joint 1 in ${}^{B}X$
S3	$|\mathrm{\Delta }{d}^t(p_2^t,p_5^t)|$	Absolute changes in the observed chest length
Shoulder elevation
S1	$a^t(p_{2/5}^1,p_1^1,p_{2/5}^t)$	Shoulder elevation angle
S2 and S3	$\mathrm{\Delta }{y}^t(p_{2/5}^t,p_1^t)$	Shoulder displacement regarding joint 1 in Y
Trunk tilt
S1	$a^t(p_8^1,p_1^1,p_1^t)$	Spine angular displacement
S2 and S3	$|\mathrm{\Delta }{H}^t|$	Absolute changes in patient’s head size