Article

Postural muscle responses are often impaired after
stroke. We aimed to identify the contribution of deficits in very early postural
responses to poorer reactive balance capacity, with a particular focus on
reactive stepping as a key strategy for avoiding falls. METHODS: A total of 34
chronic stroke survivors and
17 controls were subjected to translational balance
perturbations in 4 directions.
We identified the highest perturbation intensity
that could be recovered without stepping (single stepping threshold [SST]) and
with maximally 1 step (multiple stepping threshold [MST]).
We determined onset
latencies and response amplitudes of 7 leg muscles bilaterally and identified
associations with balance capacity. RESULTS : People with stroke had a lower MST
than controls in all directions. Side steps resulted in a higher lateral MST than
crossover steps but were less common toward the paretic side. Postural responses
were delayed and smaller in amplitude on the paretic side only. We observed the
strongest associations between gluteus medius (GLUT) onset and amplitude and MST
toward the paretic side (R2 = 0.33). Electromyographic variables were rather
weakly associated with forward and backward MSTs ( R2 = 0.10-0.22) and with SSTs
( R2 = 0.08-0.15). CONCLUSIONS: Delayed and reduced paretic postural responses
are associated with impaired reactive stepping after stroke. Particularly, fast
and vigorous activity of the GLUT is imperative for overcoming large sideways
perturbations, presumably because it facilitates the effective use of side steps.
Because people with stroke often fall toward the paretic side, this finding indicates an important target for training.

Langue : ANGLAIS