Publication Date

5-2025

Date of Final Oral Examination (Defense)

7-30-2024

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Kinesiology

Department

Kinesiology

Supervisory Committee Chair

Shawn Simonson, Ph.D.

Supervisory Committee Member

Tyler Johnson, Ph.D.

Supervisory Committee Member

Tim Kempf, Ph.D.

Abstract

Introduction: As individuals age, they are often confronted with age-related physical declines that can impede their ability to perform activities of daily living (ADLs) and elevate the risk of experiencing falls. While multiple factors may contribute to these physical decrements, muscular power diminishes more rapidly than strength across the lifespan, and serves as a more reliable predictor of fall risk among community-dwelling older adults. This early loss of power may be associated with low physical activity levels, age-related muscle atrophy, or impaired neuromuscular function; however, these findings are inconclusive. One area warranting further investigation involves exploring the contribution of different types of muscle contractions [isometric (ISO), concentric (CON), and eccentric (ECC)] to the decline in power associated with aging, particularly during high-velocity contractions. Purpose: This study aimed to compare differences in knee extension mean peak torques (mPTQs) in ISO at 0 °/s and CON and ECC at 60 °/s, 180 °/s, and 300 °/s between three female age groups. Two hypotheses were tested. (1) The older adult (OA) group would produce the lowest ECC (300 °/s) mPTQ when compared to the young adult (YA) and middle-aged adult (MA) groups. (2) ECC (300 °/s) mPTQ would be significantly lower than CON (300 °/s) mPTQ between YA and OA. Method: Twenty mobile female participants who were not physically active or following an exercise regimen were divided into three age groups: YA (n = 8, 18-28 yr), MA (n = 7, 42-52 yr), and OA (n = 5, 65-75 yr). Participants completed ISO at 0 °/s and CON and ECC at 60 °/s, 180 °/s, and 300 °/s knee extensions (dominant leg) using a Biodex System 3 isokinetic dynamometer. Descriptive statistics and analysis of variance (ANOVA) with a post-hoc Bonferroni analysis were performed using Prism software to determine statistical significance (p ≤ 0.05) for each hypothesis. One-way and two-way ANOVAs with a post-hoc Bonferroni analysis were conducted to identify differences in mPTQs within each group and among individual strength ratios between and within groups. Simple linear regressions were utilized to forecast individual CON and ECC peak torques (PTQ) based on individual ISO PTQs. Result: OA exhibited significantly lower moderate-to-high velocity ECC mPTQs than YA and MA (p < 0.05), whereas moderate-to-high velocity CONs were comparable among the groups (p > 0.05). Individual ISO PTQs can significantly predict CON and ECC PTQs (p < 0.05). Individual strength ratios were similar between the groups (p > 0.05), with some differences identified within the groups (p < 0.05). Conclusion: Older females may show reduced moderate-to-high velocity ECCs due to a slower rate of force development (RFD) during knee extensions. Factors such as decreased physical activity, limited participation in explosive movements, and age-related neurological declines may restrict their ability to activate cortical mechanisms associated with ECCs and increase reliance on weaker type I muscle fibers, accompanied by atrophied type IIa and IIx fibers. Further research is needed to investigate RFD variations, muscle firing frequency, and fiber composition among different contraction types at higher velocities in underrepresented groups to reveal additional factors that may contribute to the reduced ability to perform ADLs and increased fall risk observed among older demographics.

DOI

https://doi.org/10.18122/td.2407.boisestate

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