Recovery of Standing Balance and Health-Related Quality of Life After Mild or Moderately Severe Stroke

(A) COP excursions of paretic and nonparetic sides during arm perturbation. Data are from a single trial of a subject in the mild group. The right panel shows the nonparetic COP on an expanded scale to highlight the 95% confidence ellipse. (B) The average arm acceleration from the 20 trials (top trace) and the nonparetic and paretic hamstrings muscle activity (bottom trace) of the same subject. Note the scale is 10 times larger on the nonparetic trace (pointing up) than the paretic trace (pointing down). The electromyographic signals were aligned with the onset of arm acceleration, denoted by the solid vertical line, and subsequently averaged. The COP ellipse area (in A) and the area (filled trace), latency (dotted line), and average slope (dashed lines) of the electromyographic burst (in B) were used as outcome measures. Abbreviations: AP, anteroposterior; EMG, electromyogram; ML, mediolateral.

Electromyographic area (mean ± SE) during quiet stance in the nonparetic (top) and paretic (bottom) muscles for the mild (left) and moderate (right) groups at 1 month (open bars) and 3 months (filled bars) poststroke. Abbreviations: HAM, hamstrings; QUADS, quadriceps; SOL, soleus; TA, tibialis anterior. *Significant difference between mild and moderate groups; ^†significant difference between 1 month and 3 months.

Electromyographic burst area (mean ± SE) during the arm perturbation in the nonparetic (top) and paretic (bottom) muscles for the mild (left, n=14) and moderate (right, n=15) groups at 1 month (open bars) and 3 months (filled bars) poststroke. The number of electromyographic bursts for each muscle is shown in the bars. Abbreviations: see figure 2. *Significant difference between mild and moderate groups; ^†significant difference between 1 month and 3 months.

Electromyographic burst slope (mean ± SE) during the arm perturbation in the nonparetic (top) and paretic (bottom) muscles for the mild (left) and moderate (right) groups at 1 month (open bars) and 3 months (filled bars) poststroke. The number of bursts is the same as in figure 2. Abbreviations: see figure 2. *Significant difference between mild and moderate groups; ^†significant difference between 1 month and 3 months.

Electromyographic burst latency (mean ± SE) during arm perturbation for the (A) nonparetic and (B) paretic sides of the mild and moderate group at 1 month and 3 months poststroke. The latencies are calculated according to the start of the arm raise movement (time=0). The number of bursts included in the calculation is the same as in figure 2. Abbreviations: see figure 2. *Significant difference between 1 month and 3 months.

Average arm acceleration (top trace) and electromyographic activity (bottom 2 traces) for representative subjects from the (A) moderate and (B) mild groups at 1 month poststroke. Posterior muscle groups (hamstrings, soleus) are presented above with the corresponding anterior muscle groups (quadriceps, tibialis anterior) being presented below. The muscle activity from the nonparetic side is shown by the thick line, and the muscle activity from the paretic side is depicted with the shaded gray area. Note the difference in scale in the electromyographic traces between the left and right panels.

Activity of the leg postural muscles during arm perturbation for the same subject in the mild group from figure 6 at (A) 3 months poststroke and (B, C) a healthy subject. Both subjects are men and of similar age (≈40y). In the right panel, the healthy subject raised his right arm “as fast as he can” (100% acceleration). In the middle panel, the same subject moved his arm slower, with approximately 50% of maximum arm acceleration. Muscle activity is presented as in figure 6 with the thicker line being the nonparetic and ipsilateral side and the shaded gray area being the paretic and contralateral side. Note that the scale on the electromyographic traces has changed from figure 6.