Power Training Post-stroke

A primary impairment associated with post-stroke hemiparesis is the failure to make rapid
graded adjustment of muscle force (i.e. muscle power) within the context of purposeful
complex synergies (e.g., coordination during walking). Not surprisingly, the impact of stroke
on walking is significant, with less than 50% of survivors progressing to independent
community ambulation. Even among those who achieve independent ambulation, significant
residual deficits persist in balance and gait speed, with ~75% of persons post-stroke
reporting limitations in mobility related to walking. Muscle weakness is the most prominent
motor consequence among the nearly 6 million survivors of stroke living in the United States
and the strongest predictor of functional disability in this large clinical cohort. To date,
the physiological mechanisms that contribute to muscle dysfunction in hemiparetic subjects
are largely unstudied. Moreover, evidence regarding the efficacy of interventions aimed at
attenuating impaired muscle function and the ensuing functional consequences in the
post-stroke population is equivocal and viable therapeutic options to remediate hemiparetic
muscle weakness remain among the most pressing challenges for biomedical research. The
investigators propose that impaired muscle power (the product of muscle strength and
velocity) generation is causal of functional (walking) disability post-stroke. In addition,
coordination deficits are also critical determinants of functional performance. The
investigators have developed a comprehensive theoretical framework that defines and measures
the factors underlying disordered muscle function and coordination and will apply this
framework to Post-stroke Optimization of Walking using Explosive Resistance (POWER) training.
The investigators' goals over the four year funding period are to 1) quantify neural and
muscular adaptations that contribute to impaired muscle power generation post-stroke; 2)
assess effects of POWER training on neural and muscular adaptations in paretic and
non-paretic muscle; and 3) determine the relationship between changes in neural and muscular
adaptations following POWER training and locomotor improvements. Innovative aspects of the
proposed work include the novel training intervention; the advanced magnetic resonance
assessments; as well as the unique measure of the coordination that the investigators
propose. It is the investigators' belief that: a) neural and muscular adaptations following
stroke are associated with impaired muscle power generation as well as locomotor ability, b)
POWER training attenuates functional deficits by addressing the underlying neural and
muscular elements and c) functional improvements following training are predicated on
improving the most prominent neural and muscular contributors to muscle power generation. If
correct, the data generated will provide an entirely new level of evidence regarding the
effectiveness of this novel intervention strategy on improving functional performance as well
as the importance of peripheral muscle properties as predictors of locomotor ability
post-stroke.

Inclusion Criteria:

- age 50-70,

- stroke within the past 6 to 24 months,

- residual paresis in the lower extremity (Fugl-Meyer Lower Extremity motor score <34),

- ability to walk without assistance and without an ankle foot orthotic (AFO) on the
treadmill 30 seconds at speeds ranging from 0.3 - 0.8 m/s, and

- provision of informed consent.

- In addition, all subjects who meet criteria for the training portion must complete an
exercise tolerance test and be cleared for participation by the study cardiologist.

Exclusion Criteria:

- Unable to ambulate at least 150 feet prior to stroke, or experienced intermittent
claudication while walking;

- rating on Modified Ashworth Scale 3 at the knee or ankle;

- limited lower extremity range of motion of the knee (passive flexion Range of Motion
[ROM] < 90); hip (inability to achieve neutral 0 hip extension); or ankle (inability
to achieve 0 of active dorsiflexion);

- history of congestive heart failure, unstable cardiac arrhythmias, hypertrophic
cardiomyopathy, severe aortic stenosis, angina or dyspnea at rest or during activities
of daily living (ADLs);

- History of chronic obstructive pulmonary disease (COPD) or oxygen dependence;

- Preexisting neurological disorders, dementia or previous stroke;

- History of major head trauma;

- Legal blindness or severe visual impairment;

- history of significant psychiatric illness

- Life expectancy <1 yr.,

- Severe arthritis or other problems that limit passive ROM;

- post-stroke depression (PHQ-9 10),

- History of deep vein thrombosis (DVT) or pulmonary embolism within 6 months;

- Uncontrolled diabetes with recent diabetic coma, or frequent insulin reactions;

- Severe hypertension with systolic >200 mmHg and diastolic >110 mmHg at rest;

- Previous or current enrollment in a trial to enhance motor recovery;

- Presence of non-magnetic resonance (MR) compatible implants, pregnancy or severe
claustrophobia.