Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Medical and Health Sciences
First Supervisor
Ken Nosaka
Second Supervisor
Tony Blazevich
Third Supervisor
Jodie Cochrane Wilkie
Fourth Supervisor
Georgios Mavropalias
Fifth Supervisor
Aus Molan
Abstract
Insufficient physical activity increases non-communicable disease risk and negatively impacts mental health and quality of life. Many individuals struggle to meet recommended physical activity guidelines due to psychological, environmental, and social barriers, with a perceived lack of time being a prominent obstacle. For some occupations, such as naval submarine duty, achieving these exercise targets is even more challenging due to confined spaces and time constraints, highlighting the need for alternative exercise strategies.
Eccentric resistance exercise offers substantial health benefits with shorter time commitments than traditional (concentric-biased) exercise and may thus provide a practical solution. The present PhD project aimed to evaluate existing exercise guidelines, assess physical activity levels and barriers among submarine personnel (Literature Reviews 1 & 2), assess the severity of inactivity in the submarine environment (Study 1), investigate the feasibility and effects of a low-dose eccentric resistance exercise program on health and fitness parameters in sedentary individuals over a short (4 week) period (Study 2) and an extended 8- week period with a 12-month adherence follow-up (Study 3).
In Review 1, the benefits of minimal dose resistance exercise strategies, such as the 'Weekend Warrior' approach, single-set resistance exercise, resistance exercise "snacks," and minimal doses of eccentric resistance exercise, in enhancing muscle strength and overall fitness, particularly for sedentary individuals were examined. Barriers to exercise adherence and recommendations tailored to address these barriers were also addressed. In Review 2, the challenges of maintaining physical activity levels during prolonged submarine deployments were examined, highlighting the limited space, exercise equipment, and time available for exercise onboard submarines. It discussed the negative impacts of inactivity on submariners' health and proposes strategies, including achieving a healthy daily step count and incorporating no-load resistance training or bodyweight exercises, to mitigate these effects.
In Study 1, physical activity levels of Royal Australian Navy submariners (n=21) who had completed both onshore and on-deployment duties were surveyed. A significant decline in weekly physical activity was observed from 12.4 h/wk on land to 2 h/wk at sea. This decrease was attributed to limited space, lack of facilities, work and/or sleep related fatigue, and water usage restrictions that limit post-exercise showering opportunities.
In Study 2, a home-based, body-weight, eccentric exercise program that could be completed in 5 min was performed daily by 22 sedentary individuals (32-69 y) for 4 weeks. Each day, participants completed chair squat, chair recline, wall push-up, and heel drop exercises for 10 repetitions each using a 5-s eccentric (lowering) phase with 1-s concentric (raising) phase. The programs effects on health and fitness outcomes were assessed before and after a control period (2 weeks), and after the 4-week training period. Significant improvements in isometric mid-thigh pull strength (13.0 ± 18.5%), push-up (66.1 ± 86.5%) and sit-up (51.1 ± 78.7%) repetitions-to-failure and sit & reach flexibility (9.1 ± 20.0%) were observed, with no changes in blood pressure, fat mass, lean mass or blood related health markers. Mental health improved as evidenced by increased SF-36 scores (16.0 ± 29.0%) and subjective vitality (20.1 ± 3.2%). Importantly, participants demonstrated strong (91%) adherence to the program, reflecting its feasibility and appeal among participants.
In Study 3, the 4-week training program from Study 2 was extended by an additional 4 weeks, followed by a 12-month adherence follow-up, in a cohort of 10 participants (40-69 years) from Study 2. Participants showed further improvements in isometric mid-thigh pull strength (7.3 ± 12.2%), sit and reach flexibility (7.2 ± 11.8%), and push-up (19.5 ± 18.2%) and sit-up repetitions (28.5 ± 44.8%) after an additional 4 weeks of training. However, the gains observed during the second 4-week phase were generally smaller, indicating a tapering off in the rate of improvement. Exercise adherence remained high, with 90 ± 10% of sessions completed during the second 4 weeks. At the 12-month follow-up, 90% of participants were actively engaged in regular physical activity, demonstrating the program’s lasting impact on fostering long-term exercise habits.
Initially, the 5-min eccentric exercise program from Study 2 was planned to be conducted in submariners in Study 3. However, due to a shift in Defence priorities and changes to the Research Network for Undersea Decision Superiority (RN-UDS) funding scheme midway through the project, we were unable to investigate the effects of the program on health and fitness parameters in submariners before and after submerged deployment. Examining the effectiveness of the 5-min program on submariners would have been interesting and warrants future investigation.
In conclusion, the studies highlight the effectiveness of low-dose eccentric exercise (even much below the recommended exercise guidelines), in encouraging sedentary individuals to incorporate physical activity into their daily routines. The exercise program led to more than half of the participants initiating regular training autonomously, demonstrating its promising impact. Promoting such exercises could offer a practical solution for integrating physical activity into busy lifestyles. Given their minimal time and equipment requirements, the program appears suitable for various settings, including the submarine environment, warranting further research into its implementation in such conditions.
DOI
10.25958/y3bp-zr26
Access Note
Access to this thesis is embargoed until 11th December 2025
Recommended Citation
Kirk, B. J. (2024). Effects of low-dose eccentric exercise on health and fitness in sedentary individuals and workers with limited time. Edith Cowan University. https://doi.org/10.25958/y3bp-zr26