Concurrent validity and discriminative ability of force plate measures of balance during the sub-acute stage of stroke recovery

Background Many objective measures of balance control, including force plate measures of standing balance, lack sufficient validation for use in the stroke population. Research questions Do force plate measures of quiet standing balance during the sub-acute stage of stroke recovery have concurrent validity (i.e., correlate with functional balance measures) and discriminative ability (i.e., differentiate fallers from non-fallers and/or those with low-moderate versus high risk of falling)? Methods Participants completed one trial of quiet standing with eyes open, lasting for 30 seconds. Mean speeds of centre of pressure along the anterior-posterior and medial-lateral axes, weight-bearing asymmetry, and symmetry index were calculated. Concurrent validity of these measures were established against the Berg Balance Scale; their abilities in differentiating fallers from non-fallers, and individuals with low-moderate versus high risk of falling were evaluated using the area under the receiver operating curve (AUC). Results Among the measures studied, mean speed of centre of pressure along the anterior-posterior axis demonstrated the strongest correlation with the Berg Balance Scale (ρ=-0.430, p-value=0.01). Weight-bearing asymmetry showed the highest ability in differentiating fallers from non-fallers (AUC= 0.69), as well as individuals with low-moderate versus high risk of falling (AUC= 0.66). Significance Our findings suggest that speed of centre of pressure along the anterior-posterior axis, and weight-bearing asymmetry are valid for use in the sub-acute stage of stroke recovery. These validated measures can better inform rehabilitation practice about the ability of upright standing balance following a stroke.