Gluteus Maximus muscle activation and lower extremity power characteristics during a chair-rise in individuals following chronic stroke
Stroke is a common diagnosis frequently associated with chronic mobility deficits. Unsuccessful chair-rising is one such deficit that may persist following stroke. Thus, identification of the biomechanical requirements for the chair-rise task is necessary to generate appropriate intervention techniques. Muscle activation of the gluteus maximus (GM) and hip and knee joint power profiling during the chair-rise have been surprisingly under-investigated in adults with chronic stroke (CS). Thus, the purposes of these studies were to: 1. Investigate GM activation during self-selected natural-speed chair-rising, 2. Investigate GM activation during natural and fast-speed chair-rising, and 3. To examine hip and knee joint power, with additional investigations on the relationship with the timed up and go (TUG) test for functional mobility in adults with CS and HA.
All three cross-sectional studies used motion capture and force plate instrumentation to collect kinematic and kinetic data. For studies one and two, application of surface electromyography (EMG) to bilateral GM, hamstring (HS), and quadricep (Quad) muscles was used to investigate muscle activation characteristics. Participants were instructed to stand from a height-controlled surface onto two force plates, with one individual force plate positioned under each foot. For study one, four chair-rise trials were performed at a natural speed, and for studies two and three, four trials were also performed at a fast speed. For study three, participants also performed three trials of the TUG outcome measure.
Results of study one indicated bilateral decreased GM magnitudes in adults with CS compared to HA, with the paretic leg demonstrating a significantly delayed onset. Study two results showed similar bilateral GM deficits during fast-speeds, but with increased magnitude and earlier onset times when compared with natural speeds. Study three results indicated significant decreases in paretic knee power, but not paretic hip power for adults with CS. Also, fast-speeds yielded a significantly increased hip power, but not knee power for both groups. Lastly, no significant relationship was noted between hip or knee joint power and TUG scores for both speeds. Results indicated fast chair-rising speeds improve GM muscle activation and hip joint power output in adults with CS.