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Fuel for the damage induced: The metabolic requirements of recovery in elite rugby union match play

Hudson, J (2023) Fuel for the damage induced: The metabolic requirements of recovery in elite rugby union match play. Doctoral thesis, Liverpool John Moores University.

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The physical movement demands of rugby union have been well researched. Although the position specific skills are diverse, there are commonalities in the desirable physical attributes. Athletes possessing high amounts of functional lean mass and relatively low levels of fat mass allow actions to be performed at speed with power and repeatability. Whilst nutrition interventions to promote preparedness to perform have been investigated there is relatively little known about the metabolic requirements of recovery from match play. Resting metabolism can now be determined via indirect calorimetry under strict outpatient conditions. The appreciation of the ability to capture all mechanistic biological pathways with the metabolome and the amplification of these processes by exercise makes it an exciting method to further our understanding of the metabolic demands of elite rugby union. Finally, the intense competitive season which can last for as long as nine months of the year places unprecedented pressure on athletes to recover and perform every week. The impact of these repeated events has not been studied with reference to the ability to maintain optimal physical profiles throughout a season. Therefore the overall aim of this thesis was to determine the metabolic requirements of recovery after elite rugby union match play which will ultimately contribute to the generation of improved recovery strategies.

The aim of the first study (Chapter 4) was to investigate whether exposure to elite rugby union training and match play alters resting metabolism on a day-to-day basis throughout a competitive match week. Indirect calorimetry was performed each morning of the competitive game week, in a fasted, rested state with 22 elite rugby union players. Internal and external training loads were monitored and recorded for all sessions and video analysis was used to record contacts throughout rugby match play. Mean (SD) resting metabolic rate (RMR) increased significantly (p=0.005) the morning after match play (231± 302 kcal). There were also significant changes to mean respiratory exchange ratio (RER) after match play at GD+2 (p=0.030) and GD+3 (p=0.006) due to a significant increase in carbohydrate oxidation at rest at GD+2 (0.22± 0.13g·min-1) (p=0.044) and GD+3 (0.23± 0.13g·min-1) (p=0.003) compared with GD-1 (0.16± 0.12g·min-1) in the whole group. The monitoring of training and match loads revealed that comparable running and load metrics were experienced on training days and match days but that full collisions were not included in training. This led to the conclusion that the changes in metabolism at rest were due to the collisions experienced in match play rather than running based metabolic demands.

Having established the increased metabolic demands due to rugby union match play, the aim of the second study (Chapters 5 & 6) was to investigate the metabolic perturbations acutely and throughout recovery. Acute comparisons were made between samples collected on the day before match play and immediately post game, and the recovery comparisons were made between these same pre-match (GD-1) samples and the days following match-play. Initially, a whole body, systems-based approach of untargeted metabolomics of serum was utilised (Chapter 5). Sample collection, processing, and statistical analyses were performed in accordance with best practice set out by the metabolomics standards initiative for studies employing 700 MHz NMR spectroscopy. The results demonstrated the acute energy needs of this high intensity sport are met primarily via glycolysis, the TCA cycle and gluconeogenesis, evidenced by significant increases in serum citrate (p= 0.032) and alanine (p= 0.017) immediately post-match with significantly ranked pathways of glucose-alanine cycle (p= 0.0019), glycolysis (p=0.005), and BCAA degradation (p= 0.030). The recovery period after cessation of match play and prior to training recommencing revealed a re-entry to gluconeogenesis denoted by a significant increase in serum alanine at GD+2 (p= 0.019) and the glucose-alanine cycle highly ranked (p=0.0005) coupled with pathways of oxidative stress such as glutathione metabolism (p= 0.031), glycine-serine metabolism (p=0.042), and alterations to fatty acid metabolism. The serum metabolome implicated the need for the increased metabolic demand to be met with an increase in carbohydrate intake to appease gluconeogenesis. Further investigation was required though to further understand what the impact of the increased amino acid degradation may be and to support the findings of the serum metabolome.

The second metabolomics study (Chapter 6) employed the same untargeted methodology but in less invasive biofluids; urine and saliva. Pathways most highly ranked in saliva were aligned with findings from the serum metabolome. The glucose-alanine cycle (p= 0.008) and gluconeogenesis (p= 0.028), together with pathways of amino acid degradation (arginine & proline metabolism p= 0.042, methionine metabolism p= 0.015) were identified throughout the recovery days. The metabolism of tryptophan via the kynurenine pathway was identified in urine samples as being significantly active, both acutely (p= 0.005) and in recovery (p= 0.035), providing further evidence for the acute high energy demands of the sport and in recovery. Markers of muscle protein and connective tissue breakdown were identified as increased in the days following competitive match play. We proposed these congruent findings support the concept of upregulated gluconeogenesis in the recovery period, due to the increased requirement of carbohydrate. If not provided, via dietary intake, then the degradation of amino acids is upregulated and these may be derived from muscle protein and connective tissue due to the collision-based activities the athletes are exposed to. These multi-biofluid data therefore suggest that the increased metabolic demand reported in Chapter 4 in the days post elite rugby union match play need to be met via an increase in dietary carbohydrate intake.

Having evidenced an increased metabolic demand in recovery from match play and gained novel insight as to the metabolic pathways responsible in meeting these increased demands, we sought to answer what the impact of players potentially not meeting increased carbohydrate requirements repeatedly over the course of a whole season and how this might impact body composition (Chapter 7). The aim being to use this data to estimate longitudinal energy balance and relate this to any changes in composition with other factors of training and match exposure. Forty-six premiership rugby union players underwent DXA scanning at the start, mid-point, and end of the competitive season. Over the season from start-end there were significant increases in body mass 1.38± 2.28kg (p=0.0004)) and fat mass 1.26± 1.56kg (p=0.0001), but no significant reduction in lean mass 0.16± 1.77kg (p=0.57) in the whole group. There was, however, a loss of lean mass 0.72± 1.55kg (p=0.0055) start-mid, followed by an increase in lean mass 0.88± 1.40kg (p=0.0003) from mid-end. The forwards positional group experienced this pattern of significant variance in lean mass across the season (p=0.0042) whilst the backs saw no significant changes (p=0.2427). The loss of lean mass in the first part of the season which was typified by continuous intense weekly match play, occurred despite an estimated mean energy surplus. The gains in fat mass experienced over the season were significantly correlated with higher match exposure r= 0.6245 (p= 0.0014). This surprising finding that lean mass loss occurred despite a mean energy surplus whilst resistance training was undertaken throughout, may be because of the increased metabolic requirements in recovery. If, as we have proposed the increased demands for carbohydrate in recovery at GD+1 is not met, and the degradation of amino acids results in muscle protein breakdown acutely then a loss of lean mass can be explained. However, the concurrent mean energy surplus and gains in fat mass may be due to a desensitisation of the muscle to anabolism (termed anabolic resistance) in recovery explained by the inflammation and immunoendocrine response due to muscle damage from the collisions in match play. Further work is needed to investigate whether anabolic resistance is present in recovery and if so are there any nutritional strategies that can help overcome this.

In summary, the data presented in this thesis provide novel insights as to the increased metabolic requirements of recovery from elite rugby union match play. We propose the collisions inherent with the sport of rugby union are responsible for the significant increases in resting metabolic rate in recovery together with shifts in substrate oxidation. When investigated utilising a whole body, systems-based approach the upregulation of pathways pertaining to gluconeogenesis, amino acid degradation, and oxidative stress were revealed. The ramifications of which may compromise the integrity of muscle protein and connective tissues. The accumulation of these bouts of match play and recovery, repeated throughout a season, challenge the maintenance of optimal body compositions even when energy needs appear to be met. Nutrition interventions to shift the status quo and increase carbohydrate intakes in the day after competition may provide the necessary substrate for these metabolic requirements to be met. Indeed, elite rugby players should now ensure they are not only “fuelling for the work required” but also remember to “fuel for the damage induced”!

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Rugby; Metabolism; Sports Nutrition; Recovery; Metabolomics; Sportomics
Subjects: T Technology > TX Home economics > TX341 Nutrition. Foods and food supply
R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
SWORD Depositor: A Symplectic
Date Deposited: 10 Oct 2023 13:13
Last Modified: 10 Oct 2023 13:14
DOI or ID number: 10.24377/LJMU.t.00021635
Supervisors: Stewart, C, Close, G and Morton, J
URI: https://researchonline.ljmu.ac.uk/id/eprint/21635
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