Author ORCID Identifier

https://orcid.org/0000-0002-8570-6832

Date Available

7-20-2024

Year of Publication

2023

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Education

Department/School/Program

Kinesiology and Health Promotion

First Advisor

Dr. Fan Gao

Abstract

Background: Diabetes mellitus is associated with notable neuromuscular and motor dysfunctions that could lead to an increased risk of plantar ulcers and amputations. Several contributing factors, including increased muscle-tendon stiffness and abnormal muscle activation pattern may influence the kinematics and kinetics of walking in people with diabetes and promote formation of plantar ulcers. Hyperglycemia and the resultant accelerated rate of glycation have been recognized as the leading cause of muscle and tendon degeneration, yet the precise mechanisms by which diabetes affects the biomechanical properties of the muscle-tendon unit remains unclear. Altered muscle activity during gait is observed in people with diabetes, but its clinical utility is limited. Impaired segmental foot mobility has been noted and can be associated with high plantar pressures and ulcers in people with diabetes. Nonetheless, the existing inconsistencies in the current body of literature highlight the need for further research.

Purpose: The overall goal of this dissertation is to investigate and compare neuromuscular function in individuals with and without diabetes. Three aims are proposed. Aim 1 is to investigate in-vivo muscle tendon unit biomechanical properties in individuals with and without diabetes. Aim 2 is to examine muscle synergies in people with and without diabetes through analysis of the EMG during gait. Aim 3 is to assess gait kinematics and kinetics in individuals with and without diabetes using a comprehensive multi-segment foot and lower extremity model.

Methods: In Aim 1, morphological properties of the Achilles tendon, soleus, medial gastrocnemius, and lateral gastrocnemius muscles were evaluated by a LOGIQ ultrasound device at preset ankle (plantar flexion of 30, 15, neutral ankle position, dorsiflexion of 10 deg) and knee (90 deg of flexion, full extension) positions in both individuals with diabetes without neuropathy (DM) and non-diabetic controls (CON). A custom ankle-foot device was used to measure ankle joint passive resistance torque. In Aim 2, surface EMG data were obtained from seven lower extremity muscles during 20 barefoot walking trials. Muscle synergies were computed using non-negative matrix factorization in MATLAB. In Aim 3, a three-dimensional motion capture system and force platforms were employed to record segmental foot kinematics, as well as lower extremity joint kinematics and kinetics, throughout 20 barefoot gait trials. A four-segment foot model, including the foot, hindfoot, midfoot, and forefoot was implemented.

Results: Those with DM demonstrated significantly shorter Achilles tendon length, smaller Achilles cross section area, increased Achilles stiffness, shorter muscle fascicles for soleus, higher fascicular stiffness for soleus and lateral gastrocnemius, and higher pennation angles for all three muscles. No significant differences were observed in muscle synergies between DM and CON in terms of number of synergies, synergy complexity, or composition. Participants with DM demonstrated significant alterations in gait temporospatial parameters and kinematics including: a significantly shorter stride length, elevated hip flexion, increased calcaneal eversion, increased midtarsal dorsiflexion, and increased tarsometatarsal plantarflexion.

Conclusion: The observed alterations in gait and muscle-tendon unit biomechanical properties in the absence of neuropathy suggest a pathological process that independently contributes to neuromuscular deterioration in people with diabetes and is minimally affected by the central mechanisms of movement control. Changes in the foot and lower extremity kinematics during gait, especially decreased step length and increased calcaneal eversion, reveal the adoption of a more cautious gait and difficulties maintaining dynamic stability in this population. Further research with a specific emphasis on developing innovative therapeutic approaches for enhancing flexibility and stretching of the Achilles tendon and ankle plantar flexors, as well as improving foot mobility, holds promise for identifying novel treatment strategies to delay or prevent the occurrence of plantar ulcers.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2023.295

Funding Information

  • Teaching assistantship - Kinesiology and health promotion (KHP) department, August 2018- June 2023
  • Kinesiology and health promotion (KHP) department research award – Summer 2022
  • Kinesiology and health promotion (KHP) department research award - Spring 2021
  • Arvle and Ellen Thacker Turner Research Fund – Spring 2022
  • John E. Partington & Gwendolyn scholarship –2021-2022 Academic year
  • John E. Partington & Gwendolyn scholarship - 2019-2020 Academic year

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