The Effects of Exercise-Induced Muscle Damage With or Without Omega-3 Supplementation on Inflammation, Muscle Function and Recovery in Healthy Physically Active Younger and Older Adults

Unaccustomed eccentric exercise is associated with reductions in muscle force output, muscle pain, avoidance of repeated loading and a transient inflammatory response. Whilst exercise-induced muscle damage (EIMD) is well defined in the literature in healthy younger populations, research into older individuals is lacking. The diversity of exercise protocols used also for younger populations may not be suited to older adults. Omega-3 (n-3) supplementation may minimise EIMD via its anti-inflammatory properties, however, its efficacy remains unclear. All studies induced mild to moderate EIMD either via downhill running (Study 1 and Study 3) or resistance exercise models (Study 2 and 3), and examined the effect of n-3 supplementation (Study 1), age (Study 2), and EIMD protocols (Study 3). Venous plasma was collected for plasma creatine kinase (CK), interleukin (IL)-6, and tumour necrosis factor (TNF)-α, prior, immediately after, and 1-to-72 hours post-EIMD. In addition, at the same time points in Study 2, extracellular vesicles (EVs) were assessed. In all studies, functional measures included maximal voluntary isometric contraction (MVIC), peak power, countermovement jump, range of motion (ROM), delayed onset muscle soreness (DOMS) and thigh circumference.

Key results from Study 1 included DOMS being significantly lower in omega-3 vs placebo group (p = 0.034), and peak power significantly suppressed in placebo relative to pre-EIMD but not in omega-3 group, both at 24 hours post-EIMD. IL-6 was increased in placebo (p = 0.009) but not in omega-3 (p = 0.434) post-EIMD. However, no significant differences in peak power output and IL-6 were observed between groups. In Study 2, post EIMD, both CK and TNF-α concentrations were increased in the older group relative to the younger at 72 hours (CK, p = 0.042; TNF-α, p = 0.042). Both younger and older groups showed a significant reduction in MVIC immediately post-EIMD. EIMD did not substantially alter EV modal size or count in younger or older participants, however, the alteration in EV concentration (ΔCount) and EV modal size (ΔMode) between post-EIMD and preEIMD negatively associated with CK activity. In Study 3, a significant increase (p < 0.05) in CK was recorded in the downhill running compared with two different resistance exercise groups. Downhill running group showed greater decrements on MVIC and jump height than both resistance exercise groups post-EIMD. All groups showed a significant increase in muscle soreness post-EIMD (p < 0.001). This thesis showed that 4 weeks supplementation with 3 g/day of n-3 PUFA offsets the EIMD induced pain response following a single bout of moderate intensity exercise. Older individuals showed a blunted resolution in muscle damage and inflammation relative to their younger counterparts. However, a similar response in muscle function in both groups following EIMD was observed. The combination of the leg press and leg extension protocol with moderate intensity could be used as a muscle-injury inducing model in naive-exercised or older population in future studies.