Author Identifier

Min-Jyue-Huang: http://orcid.org/0000-0002-4268-5023  

Date of Award

2025

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Medical and Health Sciences

First Supervisor

Ken Nosaka

Second Supervisor

Favil Singh

Third Supervisor

Dennis Taaffe

Fourth Supervisor

Trevor Chen

Abstract

Cognitive function and physical fitness decline with ageing, so maintaining them is important for ensuring a high quality of life in later years. Performing regular exercises is a preventive strategy to reduce the risk of mild cognitive impairment and dementia. It might be possible that exercises focusing on eccentric (lengthening muscle) contractions in which active muscles are lengthened, provide higher cognitive demands thus stimulate the brain greater when compared with concentric exercises, in which concentric (shortening muscle) contractions are mainly performed. However, no previous study has systematically investigated the effects of eccentric exercises on cognitive function in comparison to other exercises in older adults. Thus, this research project examined: i) the effects of an acute bout of eccentric versus concentric exercises on cognitive function of older adults (Study 1); ii) changes in cognitive function and physical fitness following an 8-week eccentric exercise versus stretching training intervention (Study 2); and iii) the relationship between physical fitness and cognitive function in older women (Study 3).

Study 1: Twenty heathy elderly individuals (65-75y) preformed descending stair walking (DSW), ascending stair walking (ASW), and knee extensors resistance exercise with eccentric-only (RE-ECC) or concentric-only contractions (RE-CON) weekly in a randomised order. The Stroop tests of color naming (STCN) and conflicting color words (STCC), symbol digit modalities test (SDMT), digit span test (DST), and trail making test (TMTA, TMTB) were assessed before and after sitting for 20 min (control session) and each exercise. Significant decreases in STCN (-5.9 ± 7.4 s), STCC (-8.9 ± 11.1 s), TMT-A (-22.6 ± 9.7 s) and TMT-B (-23.1 ± 13.7 s) were observed after exercise and as well as sitting for 20 min, without significant difference among them. A significant (p < 0.05) improvement in DST score was observed after exercise for DSW (9.0 ± 17.6%) and RE-ECC (6.5 ± 10.6%), but not for ASW and RE-CON.

Study 2: Twenty-eight healthy older women (65-75y) performed either eccentric (ECC, n=14) or stretching exercise training (STRETCH, n=14) for 8 weeks. ECC consisted of seven body-weight exercises emphasising on eccentric contractions while STRETCH performed 12 stretching exercises, in supervised sessions undertaken twice weekly accompanied with a home-based program. Cognitive function tests (same as Study 1), and six physical function tests (one-leg stand: OLS, 30-s chair stand: CS, grip strength: GRIP, timed up-and-go: TUG, backwards walk: BW, 2-min step) were assessed before and after the 8-week training period and 4-week post-intervention. Fasting blood samples were collected 3 days before the first session and 4 days after the last session. STCN, TMTA and DST showed greater (p < 0.05) improvement (4.8%, 14.7%, and 10.2%, respectively) in ECC than STRETCH. All physical function tests except OLS showed greater (p < 0.05) improvement for ECC than STRETCH. Serum glucose concentration and glycosylated hemoglobin decreased (p < 0.05) in ECC only.

Study3: Using the data from the female participants in Study 1 and Study 2 (n=46), relationships between physical function and cognitive function tests were investigated. A moderate negative correlation was observed between SDMT and TUG (r= -0.442), and a weak correlation was observed between STCN and CS (r= -0.321), STCN and TUG (r= 0.386), SDMT and CS (r= 0.375), SDMT and BW (r= -0.354), and DST and Grip (r= -0.349). The SDMT score was higher (p < 0.05) for high-fitness group (52.4 ± 14.5) than the low-fitness group (41.5 ± 10.0).

These results suggest that 1) the effects of acute exercise on cognitive function are minimal in healthy older adults, but the possibility exists for a greater effect of eccentric than concentric exercises; 2) eccentric exercise intervention is more effective than stretching exercise in enhancing components of cognitive and physical function of older women; and 3) different physical fitness levels do not necessarily distinguish executive function test results, but having higher physical function appears to be positive for cognitive function in older adults. Future research should focus on longer-term effects of eccentric exercise intervention on cognitive function and mechanisms underpinning its effects.

Access Note

Access to this thesis is embargoed until 12th February 2031

DOI

10.25958/yn25-d860

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Available for download on Wednesday, February 12, 2031

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