Environmental-perturbation Balance Training Improves Functional Outcomes in Patients With Subacute Stroke

The primary outcome of this study is the improvement in neurological functional outcome at 90 days post-stroke, as measured by the modified Rankin Scale (mRS). The mRS is a 7-level ordinal scale ranging from 0 to 6, with higher scores indicating greater disability. For clinical interpretability and statistical analysis, the mRS will be dichotomized as follows: a favorable outcome is defined as an mRS score of ≤ 3 (indicating the ability to walk independently or with minimal assistance), and an unfavorable outcome is defined as an mRS score of ≥ 4 (indicating inability to walk independently and requiring assistance in daily activities). At 90 days (±7 days) after stroke, the mRS score will be assessed by trained evaluators who are blinded to group allocation, through face-to-face interviews or telephone follow-ups. The primary comparison will be the difference in the proportion of favorable outcomes (i.e., mRS ≤ 3) between the two groups.

In contrast to the primary binary outcome, the shift analysis will be able to capture the treatment effect of E-PBT on the functional prognosis of post-stroke patients more sensitively, by avoiding information loss associated with the use of a fixed dichotomization threshold.

Activities of daily living will be assessed using the Modified Barthel Index (MBI), which consists of 10 items with a total score ranging from 0 to 100. Higher scores indicate greater independence in daily living. The assessment will be administered through a structured interview to capture the patient's actual performance during the preceding week.

Balance function will be assessed using the mini-Balance Evaluation Systems Test (mini-BESTest), which consists of 14 items with a total score ranging from 0 to 28. Higher scores indicate better dynamic balance ability. This scale has been demonstrated to have good responsiveness to changes in balance function in stroke patients.

The Overall Stability Index will be measured using the balance function training and assessment system (XY-PH-V) to quantify the displacement of the center of pressure (COP) during static standing. A lower OSI value indicates better postural control ability. Since the majority of participants are unable to stand independently at baseline, this outcome will only be collected after the completion of the intervention.

Trunk function will be assessed using the Trunk Impairment Scale (TIS), which consists of three subscales: static sitting balance, dynamic sitting balance, and coordination. The total score ranges from 0 to 23, with higher scores indicating better trunk control.

The presence of pusher syndrome will be evaluated using the Scale for Contraversive Pushing (SCP). The SCP comprises the following three items: (1) asymmetry of posture, (2) abduction or extension of the non-paretic limb, and (3) resistance to passive correction of posture. Pusher syndrome is considered to be present when the score for each of the three SCP items is > 0.

The TUG will record the time (in seconds) required for the participant to rise from a chair, walk 3 meters, turn around, return, and sit down again. Shorter times indicate better mobility. The use of assistive devices is permitted during the test, but physical assistance from others is not allowed.

The 6MWT will record the total distance (in meters) that the participant can walk as far as possible within 6 minutes. If the test is terminated early due to fatigue or safety concerns, the actual distance walked and the reason for termination will be recorded.

Lower extremity motor function will be assessed using the Fugl-Meyer Assessment for Lower Extremity (FMA-LE). The scale consists of 17 items, with a total score ranging from 0 to 34. Higher scores indicate better lower limb motor function.