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Title: Growing, building and repairing elite rugby players : nutritional and energetic considerations
Author: Morehen, James Cameron
ISNI:       0000 0004 7964 2769
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2019
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It is well documented that Rugby League requires players to experience large impact collisions, repeated multiple times during training and match play, thus requiring high amounts of lean mass. To cope with such demands the pre-season period is typically used to grow and build players' to elicit improvements in body composition profiles, ready for the start of the season. Measurements of total energy expenditure and inflammation now allows a greater understanding of the in-season demands of elite level Rugby League, therefore allowing coaches to appreciate the role nutrition can play with maintaining body composition profiles developed and helping repair players during post-match recovery. The aim of the first study (Chapter 4) was to assess body composition using Dual Energy X-Ray Absorptiometry scans to identify the typical profiles of elite Rugby League players. One hundred and twelve players, from five different clubs, were split into positional groups and scanned for total mass, lean mass, fat mass and percent body fat. Despite small to very large inter-positional differences in all anthropometric variables (effect sizes = −0.08 to 2.56), particularly between the Prop and the other playing positions, there was large intra-position variation in body fat, lean mass (ES = -2.26 to 1.44) and total mass. When used with other key performance indicators, these data provide the first multiteam anthropometric profile of elite Super League players that can be used to guide individualised training and nutrition practices for current and aspiring athletes. Having assessed position specific body composition profiles, the aim of the second study (Chapter 5) was to assess what changes in body composition is possible from eleven academy players over three successive pre-season periods and ninety-nine senior players from four different clubs prior to, and at the end of, a pre-season training period. There was no meaningful change in lean mass of the academy players during any of the pre-season periods (year 1 = 72.3 to 73.2 kg; ES 0.05, year 2 = 74.4 to 75.5 kg; ES 0.07, year 3 = 75.9 to 76.8 kg; ES 0.06) with small changes only occurring over the three- year study period (72.3 to 75.9 kg; ES = 0.22). The senior players showed trivial changes in all characteristics during the pre-season period (total mass = 95.1 to 95.0 kg; ES -0.01, lean mass = 74.6 to 75.1 kg; ES 0.07, fat mass = 13.6 to 12.9 kg; ES -0.17, body fat percentage = 14.8 to 14.1 %; ES -0.19). These data suggest that academy players need time to develop towards player profiles congruent with senior players. Moreover, once players reach senior level, body-composition changes is trivial during the pre-season and therefore, teams may need to individualise training for players striving to gain lean mass by reducing other training loads. Following the pre-season period, players begin the in-season period which involves approximately 8 months of competitive league and cup fixtures. During this period, it is crucial players attempt to maintain body composition profiles achieved during the pre-season period and consume required diets to cope with the demands of match play. Therefore, the aim of third study (Chapter 6) was to assess resting metabolic rate and total energy expenditure of six elite RL players over two consecutive weeks in-season including one-match per week. Fasted resting metabolic rate was assessed, followed by a baseline urine sample before oral administration of a bolus dose of hydrogen (deuterium 2H) and oxygen (18O) stable isotopes in the form of water (2H218O). Every 24 hours thereafter, players provided urine for analysis of total energy expenditure via the doubly labelled water method. Individual training-load was quantified using session rating of perceived exertion and data were analysed using magnitude-based inferences. There were unclear differences in resting metabolic rate between forwards and backs (7.7 ± 0.5 cf. 8.0 ± 0.3 MJ. day-1). Indirect calorimetry produced resting metabolic rate values most likely lower than predictive equations (7.9 ± 0.4 cf. 9.2 ± 0.4 A most likely increase in total energy expenditure from week-1 to week-2 was observed (17.9 ± 2.1 cf. 24.2 ± 3.4 MJ. day-1) explained by a most likely increase in weekly session rating of perceived exertion (432 ± 19 cf. 555 ± 22 AU), respectively. The difference in total energy expenditure between forwards and backs was unclear (21.6 ± 4.2 cf. 20.5 ± 4.9 MJ. day-1). We report greater TEE than previously reported in rugby that could be explained by the ability of doubly labelled water to account for all match and training-related activities that contributes to total energy expenditure. To best cope with the demands of RL match play, many players try to adopt ideal nutritional strategies to maximise recovery post-match. With this in mind, the aim of the fourth study (Chapter 7) was to measure circulatory markers of inflammation, as a result of RL match play and investigate the efficacy of ingesting Montmorency tart cherry juice in an attempt to facilitate recovery post-match. Eleven professional RL players competed in 2 competitive RL matches. During both matches, a randomised cross-over design was implemented with Montmorency cherry juice (MC) or a taste and colour matched placebo (PLB) supplemented for 7 consecutive days. Measures of match-play demands including total minutes (min), relative match intensity (m.min-1), total contacts (n) and relative contacts (con.min-1), interleukin concentration (IL-6, -8, -10), muscle soreness and sleep markers (using self-reported subjective wellness), and muscle function (using jump performance) were recorded during both matches. Average IL-6, -8 and -10 concentrations all increased post-match compared with 48 h pre-match values (IL-6 = 2.95 ± 2.62 Vs 0.66 ± 0.74, IL-8 = 3.56 ± 1.55 Vs 1.96 ± 1.09, IL-10 = 2.37 ± 2.06 Vs 0.52 ± 0.49). Mean total contacts across both matches were 28 ± 11 with 0.4 ± 0.2 con.min-1. There were no significant effects of MC on muscle soreness, muscle function and self-reported sleep, fatigue, soreness, mood and stress, or IL-6, -8 or -10 compared with PLB at any of the time points. We report novel data showing no effects of MC on all measured markers of recovery post-match in elite rugby players and therefore question the efficacy of such supplementation in contact sports when players have followed a non-polyphenol depleted diet. Taken together, coaches should appreciate that in both academy and senior players, meaningful changes in body composition takes time to develop and should be viewed over one to three years instead of a single pre-season period. Total energy expenditure in senior players is greater than previously reported which has direct implications on diet prescriptions and finally, unless athletes are following a low polyphenolic diet, the use of Montmorency tart cherry juice should be questioned.
Supervisor: Close, G. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: TX341 Nutrition. Foods and food supply ; RC1200 Sports Medicine