Mapping adaptation in football

Sullivan, Adam ORCID: 0000-0003-1370-8385 (2023). Mapping adaptation in football. University of Birmingham. Ph.D.

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Abstract

Adaptation to the demands of football is a complex process. This is due to the intermittent and unpredictable nature of the game, which has numerous implications on the body (Drust et al., 2007; Reilly, 1997). Furthermore, the body is a complex biological system, where many different tissues respond in unique ways to ensure the body can cope with the demands placed upon it. These responses are also complex and begin with seemingly minor events that occur on the molecular scale. The magnitude of these responses will determine changes further up the system at the subcellular, cellular, tissue, organ system and organism scale (Wisdom et al., 2015). Consequently, practitioners and researchers attempting to understand adaptation in football are faced with a challenge that cannot be resolved with narrow views of adaptation. Broad views of adaptation are needed to capture the wide- ranging implications that occur across numerous levels in the body to this complex game.

The aim of study 1 was to explore how adaptation has been measured in football players. A scoping review was conducted. A scoping review was chosen over a systematic review as it was deemed more suitable for the exploratory nature of the study (Tricco et al. 2016; Arksey and O’Malley, 2005). In total 461 papers were analysed. From these papers, information was extracted that identifying the stimuli implemented, the study durations and frequency of measurements employed, the nature of the response to the stimuli, the outcome measures used to assess the response and the level these responses are measured at. This information was used to demonstrate that approaches to measuring adaptation seem to be dictated by pragmatic and conceptual views of adaptation, with the former approach being more common than the latter in football research.

Study 2 aimed to explore the potential for football training during the in-season phase to stimulate responses in the mechanical and physiological load-adaptation pathways. This study was an attempt to present the football stimulus in a broader way to reflect the potential implications of training on these two load-adaptation pathways. This was achieved by retrospectively classifying training sessions as ‘physiologically’ or ‘mechanically’ intense using positional GPS training data and a novel method for classifying intense sessions. This was conducted using positional data from a single season in an U23 squad in an elite football academy. For the purposes of this study it was proposed that the intensity of the training stimulus may provide the greatest opportunity for mechanical and physiological adaptations. Considering the highest volume of training players will face is during the pre-season phase, it was suggested that if physiological or mechanical adaptations were to occur in the in-season phase, it would be a product of intensity as opposed to volume.

Positional GPS data was captured across an in-season phase from an U23s squad in an elite football academy. This positional data was used to categorise and identify football training sessions that could be considered intense from a physiological and mechanical standpoint using different GPS metrics. The sessions with the highest mechanical & physiological outputs were identified for each playing position (Full backs, Centre Backs, Midfielders and Forwards). Different GPS-derived external load variables were used to categorise demands as either mechanical or physiological based on their potential to stimulate responses in these load-adaptation pathways. Sprint distance was selected as an indicator of ‘physiological’ load whilst the number of high-intensity accelerations and decelerations was selected as the indicator of ‘mechanical’ load. The 75th percentile was chosen as a separation line between intense and ‘baseline’ sessions. Therefore, any training session with an average sprint distance above the 75th percentile was considered a ‘physiological’ session.

Results demonstrated that sessions deemed intense from a mechanical and/or physiological perspective, had significantly higher demands than non-intense training sessions. Furthermore, non-intense training sessions occurred the most across the season. Thus, these significant differences may indicate that these intense sessions are different enough from more commonly occurring sessions and as such, have the potential to stimulate mechanical or physiological adaptive responses. Moreover, when these intense sessions were mapped across the season, it was apparent that players were exposed to intense mechanical or physiological sessions at different times during the season based on their playing position. Consequently, broader approaches to mapping responses are needed to understand the potential implications of training on mechanical and physiological adaptations in players of different playing positions during the in-season phase.

Study 1 acknowledged that the pragmatic views of adaptation generally favoured are understandable due to the difficulties of using time-consuming and invasive methods to measure adaptation in football players. As a consequence, many measures relating to adaptation are taken at the organism level. However, as alluded to throughout the thesis, adaptation occurs across all levels of organization in the body. Thus, more detailed insights into the processes that drive adaptive responses across numerous levels may be gained by taking measurements at the cellular level. Therefore, identifying ways to capture comprehensive insights into the complex responses to football at this level, using pragmatic approaches, is warranted.

Thus, study 3 acted as a pilot study that aimed to explore the sensitivity of change in the metabolomic response to a single intense training session in football using a novel methodology which involved capillary blood samples taken from the fingertip. These samples were analysed using untargeted metabolomics which provided insights into the energy metabolism pathways responsible for supporting the demands of a single football training session. Overall, this study demonstrated that this method was sensitive enough to detect changes in several metabolites related to energy metabolism, namely tRNA biosynthesis, glyoxylate and dicarboxylate metabolism, glycolysis, and gluconeogenesis following an intense football training session. From a methodological standpoint, this method may be an attractive avenue for future research due to the ease and speed at which these samples can be collected in the field, as well as the insights into the metabolic response to football that can be obtained.

The findings and approaches used throughout the thesis influenced the aim of Study 4. This study aimed to provide a protocol for an observational study in elite football that maps responses across multiple levels of organisation in both the physiological and biomechanical load-adaptation pathways. The aim of this study was to provide a protocol for an observational study in elite football that maps responses across multiple levels of organisation in both the physiological and biomechanical load-adaptation pathways. This study protocol demonstrates the detail required when mapping the stimulus, as well as the tissues that need to be observed and the level responses need to be measured at. This approach can help characterise the stimulus-response relationship in more detail and provide insights into the potential mechanisms behind changes in performance at the organism level. The key takeaways from this chapter are that the stimulus needs to be well defined and in detail.

This detail will help characterise the stimulus-response relationship between training and responses measured across multiple levels of organization. Outcome measures need to be measured across multiple levels of organisation to help provide insights into the mechanisms behind changes on each level as well as the potential relationship between changes across levels. Ultimately if practitioners and researchers desire to be able to understand how individuals will respond to training, these types of comprehensive approaches are required. This approach also acts as a template whereby practitioners and researchers could ‘plug in’ different outcome measures.

Type of Work:	Thesis (Doctorates > Ph.D.)
Award Type:	Doctorates > Ph.D.
Supervisor(s):	Supervisor(s) Email ORCID Drust, Barry UNSPECIFIED orcid.org/0000-0003-2092-6962 Cable, Nigel UNSPECIFIED UNSPECIFIED Robinson, Mark UNSPECIFIED orcid.org/0000-0002-5627-492X Vanrenterghem, Jos UNSPECIFIED orcid.org/0000-0002-1682-8430
Licence:	All rights reserved
College/Faculty:	Colleges (2008 onwards) > College of Life & Environmental Sciences
School or Department:	School of Sport, Exercise and Rehabilitation Sciences
Funders:	None/not applicable
Subjects:	Q Science > QP Physiology R Medicine > RC Internal medicine > RC1200 Sports Medicine
URI:	http://etheses.bham.ac.uk/id/eprint/13450

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