Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns.
Natalia Sánchez, Ana Maria Acosta, Roberto Lopez-Rosado and 2 others
PMID 28786303WHAT IT FOUND
Paretic legs show preserved hip extension and adduction strength but weak abduction and flexion.
During ankle push-off, the paretic leg involuntarily kicks the hip inward and extends the knee. This coupling may cause the body to collapse toward the affected side during balance challenges.
Key findings
01Hip extension and adduction strength were relatively preserved compared to other directions, while hip abduction and flexion were impaired.
02Maximal ankle plantarflexion in the paretic leg generated significant involuntary hip adduction and knee extension, a coupling pattern not seen in controls or the non-paretic leg.
03Muscles in the paretic leg often activated more strongly as secondary effectors (supporting other joints) than as primary effectors, with adductor activity exceeding 100% of its maximum during unrelated tasks.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
Small sample size (13 post-stroke participants analysed). The experimental setup required participants to be supported by a saddle and harness, which may not fully replicate natural free-standing balance demands. High variability in EMG signals for some muscles (gluteus maximus, hamstrings) due to noise and crosstalk. Participants were chronic stroke survivors who could ambulate; results may not apply to acute patients or non-ambulators. The study measured isometric torques in a fixed posture, not dynamic gait.
Declared interests
The authors declare no conflicts of interest. Funding was provided by the National Institutes of Health (NIH).
The easy way to misread this
Do not assume that preserved hip extension strength means the hip is functionally strong or normal. The study shows this strength is coupled with involuntary adduction and coactivation, which may actively contribute to medial collapse and falls rather than preventing them.