[Abstract Title]. - Society for Neuroscience

Title: Estimating the degree of neural activation in post-stroke muscles
Authors: T. M. KESAR 1 , R. PERUMAL 2 , A. L. MEYERS 1 , *S. A. BINDER-MACLEOD 2 ;
1 Interdisciplinary Program in Biomechanics and Movement Sci., 2 Dept Physical Therapy, Univ.
Delaware, Newark, DE
Abstract: Muscle weakness is a common consequence of stroke. It is challenging, if not
impossible, to parse the weakness in post-stroke muscles caused by atrophy versus deficits in
neural activation of muscle. Also, because post-stroke individuals cannot fully activate their
muscles, it is difficult to estimate the true force generating ability of post-stroke muscles.
In this study, we compared two methods of estimating the maximum force generating ability and
the degree of volitional activation of the paretic plantarflexor muscles in 9 post-stroke
individuals. In the 1 st method (interpolated twitch technique (ITT)), the force response to a
supramaximal electrical pulse was compared with the subject‟s muscle at rest and during a
maximum volitional contraction (MVC) to asses the degree of volitional activation (VAITT). The
VAITT and MVC values were then used to estimate the maximum force generating ability
(MaxVA). In the 2 nd method, a sub-maximal twitch to tetanus ratio (TTR) and the maximum
twitch force were used to estimate the maximum force generating ability (MaxTTR). Also, the
ratio between the MVC and the MaxTTR provided a second measure of VATTR.
Our results showed that the peak MVC forces (102.1± 46.4 N) were markedly lower than the
estimated maximum forces (MaxVA=229.8±77.0 N and MaxTTR=272.1±107.1 N). There was no
significant difference (p=0.35) between the MaxVA and the MaxTTR. The VAITT was 44.3±15.5%
and the VATTR was 44.3±33%, implying marked impairments in neural activation post-stroke.
Also, the VAITT and the VATTR were not significantly different (p=1). This study demonstrates
the ferasibility of 2 methods (ITT and the TTR) for assessing post-stroke muscle weakness. Our
results suggest that there were no differences in the estimated maximum force generating ability
and the degree of volitional activation calculated using the 2 techniques. Future work is needed
to compare the validity and reliability of these 2 techniques in post-stroke individuals.
Disclosures: T.M. Kesar, None; S.A. Binder-Macleod , Principal investigator, B. Research
Grant (principal investigator, collaborator or consultant and pending grants as well as grants
already received); R. Perumal, None; A.L. Meyers, None.
Poster
276. Voluntary Movement: Stroke, Damage, or Disease
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 276.5/KK15
Topic: D.17.a. Kinematics and muscle activity