Date of Award


Degree Type


Degree Name

Master of Science in Kinesiology



First Advisor

Christie Ward-Ritacco


Importance and Objective: Rates of physical function (PF) limitations have increased over time in middle-aged (40-64 years old) women, however the pathway to functional decline has not been fully elucidated. The aim of this study was to examine the independent contribution of muscle fatigue to physical function performance, when compared to other known contributors to PF performance.

Methods: In this cross-sectional study, 104 middle-aged women (52.93 ± 6.10 years; BMI =26.38±5.10) were assessed in their performance of a 25-repetition fatiguing task in knee flexion and extension at 180 degrees per second and muscular fatigue index (MFI) was calculated as peak torque decline from the first three repetitions to the last three repetitions. Physical function was measured objectively through six assessments (transfer task, 30 second chair stand, 6-minute walk test, 8 foot up and go, lift and carry and lower-extremity physical function composite score). Physical activity was measured using accelerometry and physical activity logs. Whole body and regional composition were measured using Dual Energy X-ray Absorptiometry. Muscle strength was assessed using isokinetic dynamometry for isometric knee flexion and extension at 60 degrees, isokinetic knee flexion and extension at 60 degrees per second and 180 degrees per second, and muscle quality (MQ) was calculated as muscle strength normalized for thigh lean mass.

Discussion: When controlling for age, percent body fat, muscle quality and moderate to vigorous physical activity (MVPA) per day, MFI was only significantly associated with transfer task performance (r=.260, p<0.05), and higher MFI was associated with slower transfer task time. While MFI contributed to 3.5% of the variance in transfer task performance (p=0.024), percent body fat contributed to 19.4% of the variance (p=0.001). Percent body fat was most highly related to all measures of physical function.

Conclusion: The strength of the association between MFI and physical function task performance decreased when other independent variables (percent body fat, MVPA, MQ) are taken into account. Therefore, muscle fatigue may be a less important target for intervention in this population, when compared to other stronger contributors to physical function.



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