The effect of a short-term potato-enriched diet on muscle protein synthesis in recreationally active men

Approximately two weeks before the commencement of the exercise-nutrition intervention, participants will undertake a 1-repetition maximum (1RM) testing on the leg-press machine. Participants will firstly be demonstrated proper lifting technique by research staff prior to engaging in 1RM testing. Participants will warm up at a self-selected load for each movement until reaching a rating of perceived exertion (RPE) of ~ 8 using a Borg Category Ratio 10 scale, for a single repetition. Thereafter, a series of single repetitions will be attempted, with 5 min recovery, until the maximal load possible for one repetition with full range of motion is determined. For the leg press, full range of motion will be established as beginning with the knees in full extension (0°), performing 90° of knee flexion, and returning to full knee extension. Participants will then be stratified and matched for one repetition maximum leg press strength (1-RM) and muscle thickness (measured via Ultrasound) into the following two dietary groups (n=10/group) matched for dietary energy and protein intake: 1) Vegan: Potato-enriched, non-animal protein (1.5-1.7 g/kg body mass [BM] of protein per day, all protein derived from non-animal based sources) 2) Omnivore: Animal-protein (1.5-1.7g/kg BM of protein per day, most protein derived from animal-based sources) The nutritional intervention will last a total of 14 full days. During this time, total energy (caloric) intake will be based on an energy availability of 45 kcal/kg Fat Free Mass per day (as based on previously published work: PMID 28855275) to ensure at energy balance state. Of this total caloric intake, participants in both groups will consume ~1.5-1.7 g/kg body mass of protein per day, ~3.5-4.0 g/kg body mass of carbohydrate per day and 1.0-1.2 g/kg body mass of fat per day. Menu construction for both dietary groups will be undertaken by Accredited Practicing Dieticians at the Nutrition and Dietetics facility at Swinburne University. Preparation and packaging of all meals and snacks will be undertaken within the kitchen facilities in room 2.10 (Building SPW) at Swinburne University. This room is approved for meal preparation within the Bachelor of Nutrition and Dietetics degree. All meals will be prepared by a professional chef and Accredited Practicing Dietitian. Every three days participants will meet with the dietician to receive new food parcels and monitor adherence to the previous days’ diet. Menus for each diet will provide three meals per day as well as “snack baskets” and post-exercise supplementation. Participants assigned to consume animal protein will consume animal-derived protein snack sources (i.e., eggs, cheese, yoghurt) with 0% protein derived from potato sources. In contrast, participants consuming the potato-based, non-animal protein diet will consume 50% of their protein from potato-based sources comprising practical, whole-food potato-based items. Food records will be kept daily by participants throughout the 14-day intervention using mobile phone applications Easy Diet Diary (Xyris Software Pty Ltd, Australia, for participants with iPhones®, Apple Inc., USA) and MyFitnessPal (MyFitnessPal Inc., USA, for participants with Android-based devices, Google Inc., USA). All dietary intake data will be analysed using FoodWorks (Xyris Software Pty Ltd, Australia) to ensure the same food database is used for all analysis. Diet records will be analysed for energy, protein, carbohydrate, and fat to provide a daily average for the entire 14-day intervention. Participants will commence supervised concurrent (i.e.: combined) exercise on Day 2 of the intervention, comprising resistance and endurance exercise on alternating days. All resistance exercise sessions will be performed in the School of Exercise and Sports Sciences gym (Building SPW, Ground Level) while all endurance sessions will be performed on a stationary ergometer in the Exercise and Sports Sciences laboratory (Building SPW, Level 1); both at Swinburne University. In total, participants will undertake six resistance exercise training sessions and six endurance exercise sessions, with each of these exercise sessions lasting approximately 40 minutes in duration. All exercise sessions will be co-ordinated by university staff members who possess experience in postgraduate exercise and sport science research and Certificate 3 and 4 in Fitness. Resistance training will consist of whole body exercises with a focus on the leg press, knee extension and bench press movements (all machine-based exercise), with these exercises to be performed at an intensity of ~60–80% of 1-Reptition Maximum. All exercises will be separated by a 3-min between-set recovery period. Endurance cycle training will be performed on Lode cycle ergometers and consist of a mixture of moderate-intensity continuous training at ~60-75% of heart rate maximum and high-intensity interval training at 100% heart rate maximum. Short, active recovery periods (1-3 minutes) will separate each ‘work’ bout. The method of allocation to be used in study will be an alternating allocation.