Combining omega-3 fatty acids with home-based resistance exercise to improve muscle health in older adults: associations, effects, and engagement

Alsowail, Abdulrahman (2026) Combining omega-3 fatty acids with home-based resistance exercise to improve muscle health in older adults: associations, effects, and engagement. PhD thesis, University of Glasgow.

Abstract

It has been predicted that worldwide the percentage of older people, aged 65 and over, globally will increase from 10% in 2024 to approximately 16% in 2050, highlighting a global shift in ageing demographics (Desa, 2019). Indeed, in the UK, from 2019 to 2030, it has been predicted that the number of older adults aged over 65 years will increase by 21.8% (Age UK, 2019). Ageing has many consequences, one of which is the progressive decrease in muscle mass and muscle strength that occurs from approximately 40 years of age and can result in sarcopenia (Dodds et al., 2014, Cruz-Jentoft et al., 2019). Recent data estimates that between 10% and 27% of those over the age of 60 years of age globally have sarcopenia (Petermann‐Rocha et al. 2022). Sarcopenia is associated with many adverse outcomes such as cardiac and respiratory diseases, an increase in mortality, falls and fractures and mobility issues which in turn may lead to the decreased quality of life and loss of independence (Cruz-Jentoft et al., 2019). Sarcopenia also has wide economic costs (Mijnarends et al., 2018).

Thus far, there is no effective pharmacological treatment for sarcopenia (Cruz-Jentoft and Sayer, 2019) and so lifestyle changes, such as diet and exercise, are often suggested. There is a wealth of literature that resistance exercise, regardless of age, can increase muscle strength and mass (Fyfe et al., 2022; Manas et al., 2021). However, many older adults in the UK are not actually engaging in resistance-based exercises (Strain et al., 2016). Therefore, a pragmatic and feasible solution is needed to improve participation and adherence to resistance exercise. Home-based resistance exercises with minimal equipment may be a practical solution. On top of this a growing body of literature indicates that supplementation with Long Chain n-3 polyunsaturated fatty acids (LCn-3 PUFA) may be beneficial. There is evidence that LCn-3 PUFA supplementation, via fish and krill oil, can increase muscle strength and muscle mass in healthy older adults (Alkhedhairi et al., 2022; Smith et al., 2015; Timraz et al., 2023). There is also evidence that LCn-3 PUFA supplementation combined with resistance exercise can improve muscle strength and physical function (Cornish et al., 2022). The improvement in muscle strength as a result of LCn-3 PUFA supplementation has been linked to enhancements in neuromuscular function (Gray & Mittendorfer, 2018; Phillips et al., 2024). However, the neuromuscular mechanisms remain unknown.

The aim of chapter 2 was to investigate the associations of n-3 fatty acid intake with handgrip strength and muscle mass indices in older adult participants from the UK biobank study. A secondary aim was to investigate whether these associations differed by physical activity status. A cross-sectional study included 53,170 participants aged 60 years and over from the UK biobank (25,324 men and 27,846 women). Higher n-3 fatty acid intake was positively associated with grip strength index in women. For each additional gram of n-3 fatty acid consumed per day, there was an increase of 0.03 kg/m2 (95% CI: 0.00 to 0.06 kg/m2) in active women and 0.04 kg/m2 (95% CI: 0.00 to 0.07 kg/m2) in inactive women. However, no significant associations were observed in men, whether active (p=0.405) or inactive (p=0.323). Additionally, no significant associations were found between n-3 fatty acid intake and muscle mass index in either active (p=0.858) or inactive (p=0.250) men, or in active (p=0.909) or inactive (p=0.187) women. Thus, the magnitude of the positive association was very small and unlikely to be clinically relevant, and normal dietary intake of n-3 fatty acid is unlikely to counteract sarcopenia and supplements may be needed.

Following this, the aim of Chapter 3 was to determine whether krill oil supplementation enhances the effects of a pragmatic home resistance exercise programme on adaptations in muscle strength (knee extensor maximal torque and grip strength) and size (vastus lateralis muscle thickness), physical function (chair rise and gait parameters) and motor unit function (firing rate, firing rate variability and neuromuscular junction instability) in healthy older adults through a double-blind RCT. A total of 46 healthy older adults aged 60 years and over participated in the study. Participants were randomised to either krill oil supplements (4g/day) plus home-based resistance exercise or placebo supplements (4g/day) plus home-based resistance exercise for 16 weeks. Knee extensor maximal torque was significantly increased by 7.8 Nm (95%CI: 0.1, 14.3, p=0.04) in the krill group with no change in the control group at 16 weeks. Firing rate variability at 10% MVC was significantly decreased by 0.01% (95%CI: -0.02, -0.00, p=0.010) in the krill group with no change in the control group at 16 weeks. No effects of krill oil were observed for other outcomes. Our data indicated LCn-3 PUFA supplementation (krill oil) can result in small but clinically meaningful improvements in lower limb muscle strength responses to resistance exercise training and that these benefits may relate to concomitant improvements in neuromuscular function. We speculate that the improvement in firing rate variability may result from the effects of LCn-3 PUFAs on enhancing the strength of common synaptic input and reducing synaptic noise.

The aim of Chapter 4 is to explore the enablers and barriers toward home-based resistance exercise in older adults. A subgroup of 10 participants aged 60 years and over (5 male and 5 female) from the 46 participants in chapter 3 were included. A semi-structured interview was carried out following the 16-week study period, during which participants performed home-based resistance exercise including both body weight and resistance band exercises. Reflexive thematic analysis approach was used to analyse the data. The analysis generated five themes: Flexibility and simplicity of home-based resistance exercise, navigating commitment, and the perceived benefits of home-based exercise were enablers for performing home-based resistance exercises. On the other hand, learning home-based resistance exercise along with indolence and procrastination were barriers. The data from this chapter indicated that physiotherapists and other exercise specialists should focus on combining body weight exercises with resistance bands and providing portable devices, like grip strength measuring devices, when they design or prescribe home-based resistance exercise, to enhance engagement in these exercises.

In conclusion, the current thesis has demonstrated that the magnitude of the association between n-3 fatty acid intake and grip strength index in older women, regardless of their activity status, which was not present in men, was small unlikely to be clinically relevant. Thus, supplementation with LCn-3 PUFAs may be needed, and krill oil, when combined with home-based resistance exercise, may offer small but clinically meaningful improvements in muscle strength and motor unit function. Furthermore, home-based resistance exercise was found to be both feasible and motivating for older adults. These findings supported the implementation of combined LCn-3 PUFA supplementation and home-based resistance exercise as a potential strategy to counteract the adverse effects of sarcopenia, although further work is needed to maximise the effectiveness of this strategy.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: R Medicine > RC Internal medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Supervisor's Name: Gray, Professor Stuart
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85884
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 20 Apr 2026 10:02
• Last Modified: 20 Apr 2026 11:20
• Thesis DOI: 10.5525/gla.thesis.85884
• URI: https://theses.gla.ac.uk/id/eprint/85884

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