Short-Term Cast Immobilization of a Unilateral Lower Extremity and Physical Inactivity Induce Postural Instability during Standing in Healthy Young Men

Abstract

Previous studies have reported an increased postural sway after short-term unilateral lower limb movement restriction, even in healthy subjects. However, the associations of motion limitation have not been fully established. The question of whether short-term lower limb physical inactivity and movement restriction affect postural control in the upright position remains. One lower limb of each participant was fixed with a soft bandage and medical splint for 10 h while the participant sat on a manual wheelchair. The participants were instructed to stand still for 60 s under eyes-open (EO) and eyes-closed (EC) conditions. Using a single force plate signal, we measured the center of pressure (COP) signal in the horizontal plane and calculated the total, anterior-posterior (A-P), and medial-lateral (M-L) path lengths, sway area, and mean COP displacements in A-P and M-L directions. The COP sway increased and the COP position during the upright stance shifted from the fixed to the non-fixed side after cast removal, compared to before the cast application, under both EO and EC conditions. These findings indicated that 10 h of unilateral lower limb movement restriction induced postural instability and postural control asymmetry, suggesting the acute adverse effects of cast immobilization.

Keywords: cast immobilization; center of pressure; movement restriction; physical inactivity.

Figure 1

Movement restriction and physical inactivity conditions.

Figure 2

Changes in postural stability before and after cast removal. (a) TPL in EO condition; (b) TPL in EC condition; (c) PL_AP in EO condition; (d) PL_AP in EC condition; (e) PL_ML in EO condition; (f) PL_ML in EC condition; (g) Sway area in EO condition; (h) Sway area in EC condition. White: before; Gray: after 10 h. * p < 0.05. The plots show individual values for all participants. TPL, total path length; PL_AP, anterior–posterior path length; PL_ML, medial–lateral path length. EO, eyes open; EC, eyes closed. The graphs represent average values.

Figure 3

Changes in directional specificity of postural control before and after cast removal. (a) mean COP displacement_AP in EO condition; (b) mean COP displacement_AP in EC condition; (c) mean COP displacement_ML in EO condition; (d) mean COP displacement_ML in EC condition. White: before; Gray: after 10 h. * p < 0.05. The plots show individual values for all participants. The graphs represent average values. COP, center of pressure; AP, anterior–posterior; ML, medial–lateral; EO, eyes open; EC, eyes closed.