Abstract
BackgroundThe abnormal synergy seen in patients after stroke is considered to limit the ability of these patients. However, in the lower extremity, antigravity torque generation rather than precise movement is needed for functions such as sit-to-stand movement and gait. Therefore, the ability to generate torque may be important either as a primary movement or as an abnormal synergy. We attempted to quantify the torque generation in the lower limb, selectively and as an abnormal synergy, and its relation with gait.MethodsSelectively generated plantar flexion torque in the ankle and plantar flexion torque secondarily generated accompanying maximal hip extension (i.e., torque generated with abnormal synergy) were measured in subjects after stroke and control subjects. In subjects after stroke, secondary torque generation while controlling hip extension torque as 25%, 50%, and 75% of the maximal hip extension was also measured. The relation of torque generation with the gait speed and timed-up-and go test (TUG) was also analyzed.ResultsIn subjects after stroke, there was no difference between the amount of plantar flexion torque generated secondarily and the selectively generated torque, whereas the selective torque was significantly greater in control subjects. Pearson product–moment correlation coefficient analysis revealed that TUG speed is related to secondarily generated torque accompanying maximal hip extension but not with selectively generated torque.ConclusionSecondarily generated torque was found to be a factor that affects TUG speed, and the ability to generate torque even through abnormal synergy may help for gait ability in subjects after stroke.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-141) contains supplementary material, which is available to authorized users.
Highlights
The abnormal synergy seen in patients after stroke is considered to limit the ability of these patients
The 50%secondarily generated plantar flexion torque (STo) was higher than the 25%STo, and the STo was higher than the 75%STo
The PTo was significantly higher than the STo in the Characteristics of primary torque and secondary torque in the subjects after stroke and the control group In a previous study that measured the secondary torque in the ankle joint during maximum voluntary hip extension in both controls and subjects after stroke, the secondary torque was seen in both groups and no differences were found in the rate of the secondary torque to maximum voluntary ankle plantar flexion torque between the groups [13]
Summary
The abnormal synergy seen in patients after stroke is considered to limit the ability of these patients. We attempted to quantify the torque generation in the lower limb, selectively and as an abnormal synergy, and its relation with gait. In a study quantifying the upperlimb abnormal synergy in patients after stroke, Dewald et al [28,29] measured the joint torque that the subjects were attempting to maximize as the primary torque and the torques at other directions as secondary torques, along with electromyographic (EMG) measurements during voluntary isometric muscle contractions. They found that patients after stroke had significantly decreased maximum voluntary torque compared with the control subjects, and that the patients exhibited reductions in maximum torques when required to control the secondary torque [28,29]. Other studies that applied a similar method to the lower limb [13,14] suggested that the primary contributor to lower-limb motor deficits was the weakness of voluntary torque rather than the value of abnormal synergy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
