How the gut microbiome affects your ability to increase muscle size with weight training.

This study will comprise two arms, a resistance training only arm (RT) and a resistance training with creatine supplementation arm (RT+CR). The RT intervention for both arms will be conducted face-to-face in the research and teaching gym at the Department of Exercise Physiology, School of Health Sciences, Faculty of Medicine and Health, Wallace Wurth Building, Kensington Campus, the University of New South Wales (UNSW), Sydney. Imtiaz Desai (ID) will be responsible for the programming and supervision of the exercise intervention. He is a qualified exercise scientist with significant experience in administering exercise programs and assessments. Exercise sessions will be conducted in the early mornings, lunch times, and after business hours to avoid clashes with business hours. RT INTERVENTION Both arms will follow the same RT intervention procedures. The program will be designed to elicit whole-body skeletal muscle hypertrophy, and will include the following variables: 1. Three one-hour RT sessions a week for 12 weeks, with at least one day of rest between sessions, to provide an adequate volume of training with sufficient recovery between sessions. 2. A training intensity that requires the participant to move the heaviest weight possible for 8, 10 or 12 repetitions (8-12 rep max) will be prescribed to provide an adequate training stimulus. A different rep max (8, 10 or 12) will be used on each session of the week. The rep max method will be used to ensure that the intensities (loads lifted) are relative to the individual's abilities, while standardising the intensity prescribed across all participants. To adhere to the 8-12 rep max, an individual's rating of perceived exertion (RPE) on a Likert scale of 1-10 will be recorded during two warm-up and all working sets. RPE corresponds to the amount of repetitions an individual perceives they will be able to perform after the set is complete, where an RPE 5 equates to 5 reps more, RPE 6 is 4 reps more, RPE 7 is 3 reps more, and so on. An individual's loads will therefore be adjusted per set during each session using their RPE to adhere to the prescribed rep max for the session. 3. Three sets per exercise and five exercises per session (two lower and three upper body movements) will be prescribed to ensure an adequate volume of full body movements. Examples of lower body exercises to be prescribed include the leg press, curl and extension machines, lunges, and weighted squats. Upper body movements to be prescribed will include the chest press machine, shoulder press variations, seated row, lat pull down and dumbbell row. Movements for the elbow joint to be prescribed will include the bicep curl and cable triceps extensions. 4. To record adherence, the following information will be recorded at each session: a. Sets and repetitions completed for each exercise b. RPE for each set c. Adverse reactions following the previous session d. If a participant misses a session, and there are alternate times within that week to schedule a make-up session (based on room, participant and investigator availability), a make-up session will be scheduled. To adhere to the study’s timeline, make-up sessions will not roll over to following weeks. However, given that research indicates that at least two RT sessions a week are needed for muscular hypertrophy, three sessions have been selected to account for potential missed sessions. All missed sessions will be recorded for adherence reporting.