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.