ORCID

0009-0006-6595-6822

Keywords

Grip Strength, Older Adults, Sarcopenia, Brain Health, Electromyography, Motor Units

Abstract

Recent evidence suggests that grip strength is a critical biomarker of brain, muscle, and metabolic aging. To date, neuromuscular properties related to individual motor unit size and firing rates have not been explored in the context of grip strength assessments in the older adult population. Given the strong correlation between grip strength and all-cause mortality, understanding motor unit characteristics during maximal grip tests will provide novel perspectives and implications regarding healthy aging. The purpose of this dissertation project was to develop an analytical framework to reliably characterize motor unit strategies employed during maximal grip strength tests, and compare these characteristics between weak and non weak older adults. Study 1 explored the reliability of linear and exponential regression model coefficients derived from motor unit peak firing rate and action potential amplitude relationships during maximal grip strength tests. Results demonstrated moderate-to-excellent intrasession and poor-to-good intersession reliability among key model coefficients, despite poor reliability for the number of motor units used to create the regression models. Study 2 sought to compare key regression model coefficients between weak and non-weak older adults in a single grip testing session. Results from this study show significantly higher peak firing rates, slopes, and decay factors for the non-weak group, which may indicate potential down-regulation of higher threshold motor units among weak older adults. Individuals in the non-weak group also reported significantly higher engagement of vigorous exercise activities compared to the weak group. Study 3 employed a randomized-controlled, double-blind design to explore the potential of combined action observation/mental imagery and transcranial direct current stimulation to modulate motor unit firing rates among older adults. Results from this study indicate no group differences, however lower grip strength was observed among all groups following the intervention period.

Completion Date

2025

Semester

Summer

Committee Chair

Stock, Matt

Degree

Doctor of Philosophy (Ph.D.)

College

College of Health Professions and Sciences

Department

Kinesiology

Format

PDF

Identifier

DP0029519

Language

English

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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