Pedaling alters the excitability and modulation of vastus medialis H-reflexes after stroke.

OBJECTIVE: Individuals post-stroke display abnormal Group Ia reflex excitability. Pedaling has been shown to reduce Group Ia reflexes and to normalize the relationship between EMG and reflex amplitude in the paretic soleus (SO). The purpose of this study was to determine whether these changes extend to the paretic quadriceps. METHODS: H-reflexes were used to examine Group Ia reflex excitability of the vastus medialis (VM). H-reflexes were elicited in paretic (n=13) and neurologically intact (n=13) individuals at 11 positions in the pedaling cycle and during static knee extension at comparable limb positions and levels of VM EMG. RESULTS: VM H-reflexes were abnormally elevated in the paretic limb of stroke survivors. During static muscle activation, H-reflex amplitude did not change with the level of background VM activity. Pedaling reduced the amplitude of paretic VM H-reflexes and restored the normal relationship between VM EMG and H-reflex amplitude. CONCLUSIONS: Pedaling-induced changes in Group Ia reflex excitability that have been reported for the paretic SO are evident in the paretic VM. Pedaling may have a generalized effect on lower extremity Group Ia reflexes post-stroke. SIGNIFICANCE: Pedaling may be therapeutic for reducing Group Ia reflexes after stroke.

Lower extremity passive range of motion in community-ambulating stroke survivors.

BACKGROUND: Physical therapists may prescribe stretching exercises for individuals with stroke to improve joint integrity and to reduce the risk of secondary musculoskeletal impairment. While deficits in passive range of motion (PROM) exist in stroke survivors with severe hemiparesis and spasticity, the extent to which impaired lower extremity PROM occurs in community-ambulating stroke survivors remains unclear. This study compared lower extremity PROM in able-bodied individuals and independent community-ambulatory stroke survivors with residual stroke-related neuromuscular impairments. Our hypothesis was that the stroke group would show decreased lower extremity PROM in the paretic but not the nonparetic side and that decreased PROM would be associated with increased muscle stiffness and decreased muscle length. METHODS: Individuals with chronic poststroke hemiparesis who reported the ability to ambulate independently in the community (n = 17) and age-matched control subjects (n = 15) participated. PROM during slow (5 degrees/sec) hip extension, hip flexion, and ankle dorsiflexion was examined bilaterally using a dynamometer that measured joint position and torque. The maximum angular position of the joint (ANGmax), torque required to achieve ANGmax (Tmax), and mean joint stiffness (K) were measured. Comparisons were made between able-bodied and paretic and able-bodied and nonparetic limbs. RESULTS: Contrary to our expectations, between-group differences in ANGmax were observed only during hip extension in which ANGmax was greater bilaterally in people post-stroke compared to control subjects (P