This study will be a randomised, double-blind trial where participants will be randomly assigned to consume either a i) vegan whey protein; ii) a whey protein; or iii) a non-protein carbohydrate control supplement for 3 days following strenuous eccentric knee extension exercise. For the duration of the study period, participants will orally consume deuterated water stable isotope tracer (D2O). This, together with repeated blood sampling and muscle biopsies will allow for the calculation of free-living myofibrillar protein synthesis rates under conditions of rest and over 24-, 48- and 72-hours post-exercise recovery.

Participants will be asked to attend 7 experimental visits at the School of Sport, Exercise and Rehabilitation Sciences at the University of Birmingham. The first of the 7 visits will be to assess participant eligibility and to gain written informed consent, where the remaining 6 visits will involve experimental procedures. Briefly, participants will be randomly assigned to ingest one of three nutritional supplements (i: vegan whey protein isolate; ii: whey protein isolate; iii: a non-protein carbohydrate control), 3 times a day for a total of 3 days following an acute bout of unilateral lower-limb eccentric exercise. The study will be run in a double-blinded fashion, where the researchers and participants will both be unaware of nutritional treatment allocation. The amount of protein in each supplemental beverage is prescribed based on total body mass (0.3 g of protein per kg of body mass). As well, for 3 days before and 3 days after the exercise bout, participants will be provided with a standardised diet to consume. For the 3 days before the exercise bout, all participants will consume an identical diet, with a protein intake of 1 g per kg body mass and diets will be energy-matched between treatment groups. For the subsequent 3 days, participants assigned to each of the protein supplementation groups (whey protein or vegan whey protein) will have a daily protein intake of 1.9 g per kg body mass, whereas participants assigned to the carbohydrate control group will maintain protein intake at 1 g per kg body mass. Measures of muscle function, soreness and thickness will be taken before and at various time points after the eccentric exercise, details of which can be found below. To assess the muscle protein synthetic response to each nutritional treatment, participants will orally consume a stable isotope tracer ("heavy water") for a period of 9 days, and muscle biopsies and saliva samples will be taken periodically. An outline of each experimental visit is outlined below.

Inclusion Criteria:

• Males, and females aged 18-40 years with a body mass index between 18.5 and 29.9 kg/m2
• Healthy individuals free from metabolic and respiratory disease
• Recreationally active or trained (complete at least 150 mins of moderate physical activity, or 75 mins of vigorous physical activity per week, identify with a certain sport, intend to compete in local competition)
• Understands and is willing, able and likely to comply with all study procedures and restrictions
• Demonstrates an understanding of the study and willingness to participate, as evidenced by voluntary written informed consent

Exclusion Criteria:

• Aged <18 or >40 years
• Pregnancy and Breastfeeding
• Body mass index <18.5 or >29.9 kg/m2
• Regular participation (i.e., >3 times weekly for the previous 3 months) in structured exercise or sport with a large eccentric component, such as trail running, soccer, basketball etc.
• Elite athletes or sports-people who compete nationally or internationally
• Habitual smokers
• History of respiratory or metabolic disease
• Any allergies or intolerances to the study materials, protein supplements and food ingredients to be used in this study. In particular, those with an allergy to lidocaine and lactose will be excluded
• Use of any medication or supplements known to affect muscle protein metabolism (e.g., beta-blockers, corticosteroids, analgesics, or non-steroidal anti-inflammatories). Additional medications and/or supplementation aids (e.g., vitamins) will be deemed inappropriate based on the PI's discretion
• Any current or history of musculoskeletal injury
• Any history of medical or surgical events that may affect the study outcomes
• Previous participation in a research-based exercise protocol designed to induce severe muscle damage in the last 6 months
• Habitual protein intakes <0.8 g/kg body mass/day or > 2.2 g/kg body mass/day