Award Date


Degree Type

Doctoral Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Committee Member

Jing Nong Liang

Second Committee Member

Daniel Young

Third Committee Member

Kai-Yu Ho

Fourth Committee Member

Merrill Landers

Number of Pages



Purpose/Hypothesis: The hallmark gait deviation in individuals with post-stroke hemiparesis is slow walking speed. Reduction in gait speed after stroke is influenced by decreased propulsive forces, which may likely be related to impaired spinal circuit function and spasticity of the paretic plantarflexors. Chronic muscle tone maladaptations in paretic ankle plantarflexors can result in altered Achilles tendon (AT) morphology, therefore leading to altered mechanical properties, force transmission capabilities and subsequent insufficient propulsive forces during walking. The purpose of this study is to characterize the chronic maladaptations in both the spinal Ia afferent loop excitability and AT morphology after stroke lesions in the brain in individuals with chronic post-stroke hemiparesis.

Materials and Methods: Nineteen non-neurologically impaired individuals and fifteen neurologically impaired individuals participated in this study. Ultrasound imaging was conducted, acquiring two views at three locations along bilateral ATs to measure tendon thickness, cross-sectional area (CSA), and collagen fiber organization. Spinal Ia afferent loop excitability was assessed by measuring the soleus (SOL) H-reflex amplitude. Surface electromyography of the tibial nerve was recorded using surface electrodes on the SOL muscle to obtain a recruitment curve. Peak-to-peak amplitudes of the H-reflexes were averaged, and expressed as Hmax/Mmax. Outcome measurements to assess spasticity and level of function in individuals with post-stroke hemiparesis were also performed. Additionally, all individuals participated in a 10-Meter Walk Test (10MWT) to assess gait speed. One-way ANOVAs with repeated measures and post hoc analyses were conducted to compare the tendon morphology and H-reflex amplitudes of the paretic and non-paretic limbs in individual with post-stroke hemiparesis, as well as the non-impaired limb (right limb) in non-neurologically impaired individuals.

Results: We observed significantly greater thickness of the AT at the calcaneal insertion and midportion, as well as increased collagen fiber disorganization at the calcaneal site of the paretic limbs when compared to non-neurologically impaired limbs. It was also observed that individuals with chronic post-stroke hemiparesis had slower self-selected walking speeds compared to the non-neurologically impaired individuals as measured via the 10MWT (p < 0.05). No significant difference in CSA was found amongst the groups. No statistically significant differences in Hmax/Mmax ratios were found in the paretic legs compared to the non-paretic and non-impaired legs in the paretic limbs of individuals post-stroke.

Conclusion: This study found that tendon thickening and increased collagen fiber disorganization in the insertion site of the AT were present in the paretic limb, which may explain the reduction in propulsive forces needed for adequate gait speed in individuals with post-stroke hemiparesis. Our findings also depict no significant difference in Hmax/Mmax ratio in the paretic limb of individuals with post-stroke hemiparesis compared to non-neurologically impaired individuals. The changes in H-reflex excitability of the paretic plantarflexors and altered morphology observed in the paretic Achilles tendon potentially underlie post-stroke walking deficits. Thus, future rehabilitation programs should consider adopting an integrated approach addressing both neurological and mechanical deficits to restore walking function in individuals chronically post-stroke.


Stroke; CVA; Gait; Achilles; Achilles tendon; Walking speed; Sonography; H-reflex; H max/m max; H/m ratio; Hemiparesis


Biomechanics | Neurology | Physical Therapy

File Format


File Size

1160 KB

Degree Grantor

University of Nevada, Las Vegas




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