Over their lifespan, many individuals experience episodes of skeletal muscle-disuse due to illness, injury, or elective surgery. Periods of prolonged skeletal muscle disuse, such after ACLR, result in the loss of skeletal muscle mass (atrophy) and strength. Skeletal muscle disuse precipitates several metabolic and functional impairments. Importantly, as the Canadian health care system shifts towards day surgeries and outpatient settings as opposed to in-hospital care, the development of patient-led strategies to mitigate skeletal muscle disuse atrophy has become increasingly vital.

For most ACLR outpatients, resistance exercise is not feasible in the immediate 2-week post-surgical period, during which the rates of skeletal muscle mass and strength loss are highest. Outside of pharmacology, nutrition represents one alternative strategy to combat skeletal muscle-disuse atrophy during this time. Previous work reported that daily supplementation with EAA prior to and after total knee arthroplasty surgery attenuated skeletal muscle atrophy and enhanced recovery of functional mobility in adults. Similarly, chronic daily supplementation with omega-3 fatty acids reduced declines in quadriceps volume in healthy, young women during single-leg immobilization. This finding complemented previous work in which supplementation with omega-3 fatty acids potentiated muscle protein synthesis rates in response to an hyperaminoacidemic-hyperinsulinemic clamp, but not fasting rates in healthy younger, middle-aged, and older adults, while it additionally improved skeletal muscle strength and power. Together, these data suggest that combined intake of omega-3 fatty acids and EAAs may be an effective strategy to combat skeletal muscle-disuse atrophy, and perhaps loss of skeletal muscle strength, in response to ACLR.

Whilst there is a growing body of literature to promote EAA and omega-3 fatty acids as anabolic stimuli, no work has explored the combined effect of these nutritional strategies in the pathophysiological context of surgery. Nutritional strategies represent an accessible treatment for skeletal muscle disuse atrophy that is independent of patient age, mobility, or current health status, which could prove favourable for surgical outpatients, as well as individuals experiencing periods of prolonged immobilization or bed rest. The future goal of this design is to test efficacy of the combined nutritional strategy of daily omega-3 fatty acid and EAA supplementation to attenuate of skeletal muscle disuse atrophy following elective knee surgery. However, the aim of the present randomized controlled pilot trial is to explore the feasibility of recruitment and retention of adult ACLR outpatients from a single centre across 18 months for a protocol that prescribes combination omega-3 fatty acid and EAA supplementation vs. a calorie- and nitrogen-matched placebo control supplement 4 weeks before and 2 weeks after ACLR surgery. This pilot will also characterize measurements of skeletal muscle volume, strength, and function, and integrated rates of skeletal muscle protein synthesis, as well as report participant adherence to protocols and the incidence of adverse events. The investigators envisage that the data generated from this trial will be used to inform the future large scale randomized controlled trial (RCT) that will examine the effect of the combined nutritional intervention on skeletal muscle volume and functional outcomes in response to ACLR. The results of future work may inform clinical practice and outpatient care guidelines to minimize loss of skeletal muscle mass and strength in response to elective surgery.