Football Science and Performance Coaching E-Book

Adam Owen

• Herausgeber: Meyer & Meyer Sport
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2023

Seitenzahl: 826

Beschreibung

In recent decades, the sporting landscape has seen many changes, notably the inclusion and professionalization of sport science and coaching. With this change has come significant demand for applied research surrounding soccer science and performance coaching, leading to new theory and methodology across all aspects of the game. This book brings together the most fundamental components of soccer science and performance coaching through modern, integrated coaching science methods implemented by leading practitioners and researchers. The expertise included in this book provides a unique blend of modern, soccer-specific research trends with innovative coaching theory, implemented at an elite level, and enhances the knowledge of coaches and medical and performance specialists, all while advocating an applied alternative to the development of players. Within each of the main sections—Prepare, Perform, Recover—leaders in the fields of applied sport science, sport and exercise science, sport psychology, sport nutrition, and strength and conditioning outline the best coaching and training methods, making this book a must-have for coaches and trainers seeking to augment their own understanding of what is required to enhance player development.

Leseprobe

Dr. Adam Owen (Ed.)

FOOTBALL SCIENCE &

PERFORMANCE COACHING

Develop an Elite Coaching Methodology With Applied Coaching Science

PREPARE • PERFORM • RECOVER

Meyer & Meyer Sport

British Library of Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

Football Science & Performance Coaching

Maidenhead: Meyer & Meyer Sport (UK) Ltd., 2024

9781782555346

All rights reserved, especially the right to copy and distribute, including the translation rights. No part of this work may be reproduced–including by photocopy, microfilm or any other means–processed, stored electronically, copied or distributed in any form whatsoever without the written permission of the publisher.

© 2024 by Meyer & Meyer Sport (UK) Ltd.

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Credits

Cover and interior design: Anja Elsen

Layout: DiTech Publishing Services, www.ditechpubs.com

Cover photo: © AdobeStock

Interior stock images: © AdobeStock, unless otherwise noted

Interior photos and figures: All photos and figures provided by the authors, unless otherwise noted

Infographics: From Yann Le Meur, www.ylmsportscience.com

Managing editor: Elizabeth Evans

Copy editor: Sarah Tomblin, www.sarahtomblinediting.com

9781782555346

Email: [email protected]

www.thesportspublisher.com

The content of this book was carefully researched. All information is supplied without liability. Neither the authors nor the publisher will be liable for possible disadvantages, injuries, or damages.

CONTENTS

Foreword by Steve McClaren

Preface

Introduction: Applying Science in Coaching

Chapter 1The World Through Football

Football – Just a Simple Game?

Socio-Cultural Factors on Player Development

PRERAREFootball Demands – Ready or Not?

Chapter 2Demands of the Game

Football Characteristics and Game Demands

Player Anthrompometry

Cardiovascular Fitness and Aerobic Capacity

Strength and Power Demands

Jumping Power and Explosive Ability

Sprint Capacity Profiles in Football

Competition Requirements

Contextual Factors of Football

Chapter 3Women’s Football Requirements

Competitive Match Demands

Physical Characteristics and Capacity

Training Considerations

Nutritional Considerations of the Female Football Athlete

Menstrual Cycle and Performance

Chapter 4Physiological Response to Football Performance

Match-Play Effects on Haematological Profiles

Long-Term Training Effects on Haematological Profiles

Effects of Acute Football Matches and Long-Term Football Training on Hormonal Markers

Long-Term Effects of Football Training on Hormonal Markers

Effects of Acute and Long-Term Football Match Training on Inflammatory and Muscular Damage Markers

Relationships Among Haematological, Hormonal, Inflammatory and Muscle-Damage Biomarkers With Physical Performance After Longitudinal Football Training

Practical Applications

Chapter 5Psychology and Mental Skills Training in Football

Integration of Psychological Preparation

Psychological Preparation

Mental Skills Training

Time Management and Pre-Performance Routines

Social Skills Training

Mental Training and Biofeedback

Perceptual-Cognitive Training

Psychological Periodisation

Chapter 6Developing Creative Players

Developmental Trends of Creativity in Football

Developing a Multidimensional Approach

Creativity Developmental Framework (CDF)

Implications for Coaching Practice

Chapter 7Decision Making, Visual Perception and Cognitive Effort in Football

Decision Making in Football

Systemic Thinking

Visual Search Behaviour

Cognitive Effort Perspective

Cognitive- and Tactical-Based Effort in Football

Chapter 8Enhancing Skill Adaptation in Football

Skill Acquisition Through the Ages

Principles of Ecological Dynamics

Constraints-Led Coaching in Sport

Transferring Theory Into Practice

Application of the PoST Framework

Chapter 9A Modern Method and Process for Youth Development in Football

Long-Term Athletic Development

Traditional Versus Holistic Training Approach

Physical Qualities

Skill Acquisition and Conditional Framework

Planning to Perform: LTAD

Body Awareness – Core and Breathing

PERFORMTesting & Monitoring – Driving Productivity

Chapter 10Training Load Management in Football

Understanding Training Load

A Practical Model for Workload Monitoring

Application of Training Load Monitoring in Coaching

Load Management Considerations

Chapter 11Invisible Testing and Monitoring in Football

Monitoring Fatigue in Elite Football

Daily Monitoring – A Working Example

Reducing the Time-Related ‘Workload’

Developing a Modern, Contextual Monitoring System

Developing Trust – Messaging Correctly

Chapter 12Critical Moments of Match Play

Evolution and Analysis of Peak Match Demands

Critical Moments and the Key Concepts

Intermittency and Peak Match Demands

Critical Power Concept in Football

Chapter 13Performance Analysis and the Artificial Intelligence Teammate

Data Collection in Football

Maximising Game-Related Data Sets

Artificial Intelligence and Performance Links

Artificial Intelligence and Injury Analysis

Chapter 14Football Periodisation

Periodisation Theory

Traditional Approach to Periodisation

Block Periodisation in Football

Systemic Football Periodisation Models

Contextual Periodisation Models in Football

Chapter 15Strength and Conditioning in Elite Football

Strength and Conditioning Requirements of the Game

Understanding the Outcomes of S&C

The Importance of Postural Strength

Football-Specific Strength Movements

Introducing Power Movements

Programming Strength Work

Off-Season: Developing Strength Foundations

In-Season: Micro-Dosing Strength and Power to Develop Competitive Advantage

Chapter 16Game-Based Training Interventions

Various-Sided Games as a Training Tool

Acute Effects of Various-Sided Training Games

Adaptation Effects From Training Games

Practical Interventions and Coaching Perspectives

Match Play and SSGs Comparison

SSGs for Technical and Tactical Development

Chapter 17Football-Specific Endurance Training

Energy Demands in Football

Endurance Training Methods: Traditional vs. Modern

Endurance Evaluation

Considerations for the Practice Design

Chapter 18Speed and Agility Development in Football

Understanding Football Speed

Understanding Speed and Agility

Understanding Acceleration and Deceleration

Maximal Velocity (Vmax) Running

Changing Directional Mechanics

Chapter 19Developing a Football Training Methodology

Microcycle Tapering and Periodisation in Football

Microcyle-Tapering Strategy

Application of an Integrated Coaching Process

Chapter 20Training and Technical Load Monitoring in Football

Technical Actions in Professional Football Match Play

Technical Load Monitoring Within Football Conditioning

Incorporating Technical Actions Into Training Performance

Chapter 21Developing a Tactical Strategy in Football

Tactical Systems and Principles of Football

Understanding the Game Moments

Analysis of Success (I)

Analysis of Success (II)

RECOVERBody and Mind for Football – Fuel to Fly

Chapter 22Football Nutrition for the Elite Player

Football Physiology for Nutritional Understanding

Understanding Macronutrients for Performance

Fluid Balance and Football-Specific Hydration

Nutrition for the Female Football Player

Vegetarian and Vegan Considerations for Football Players

Football-Specific Supplementation and Ergogenic Aids

Nutritional Periodisation

A Pragmatic Individualised Performance Nutrition Approach to Football

Chapter 23Recovery Training and Strategies in Elite Football

Football Fatigue and Application of Recovery

Using Recovery Strategies in Football

Future Directions of Recovery Strategies

Recovery Periodisation

Chapter 24Fixture Congestion in Professional Football: How Much Is Too Much?

Understanding the Impact of Fixture Congestion on Performance

Technical and Tactical Performance

Recovery Kinetics

Injury Risk

Practical Applications and Strategies to Maximise Performance

Chapter 25Injury Analysis in Football

Injury Occurrence – Effect of Gender and Age

Injuries and Potential Consequences

Rehabilitation and Return to Play After Injuries

Injury Prevention in Football

Chapter 26Rehabilitation in Football

The Neuromuscular Consequences of Injury, Immobilisation and Disuse After Injury

Principles of Rehabilitation and Retraining Strategies

Strength Assessment and Monitoring in Rehabilitation

Pain and Load Management in Football

Chapter 27Tactical Integration in the Return to Play Process

Understanding the Game Demands for RTP

Return to Play (RTP) Considerations

Practical Interventions for RTP

Positional Demands of the RTP Process

Return to Play Periodisation

Practice Design Process of the RTP Stage

About the Editor

About the Contributors

FOREWORD

Throughout my career in the game as a coach, assistant manager and manager, one of the greatest shifts within the game itself has come through the integration of sport science. The influence it has in the game across many areas and club departments is significant. Increasing performance and exploring the finer details to gain a competitive advantage is something towards which every coach aspires. The education aspects of football science are fundamental and, in some cases, still underdeveloped and under-utilised; however, with every passing season, it becomes more evident within the top teams’ preparation, performance and recovery.

This book brings together many different components of high-performance coaching and, as a result, provides readers with an insight into how the game is evolving – not only from a training perspective, but also from the influence on competition. Understanding the tactical demands of the game is significant to all individuals wanting to improve their work in the game; however, how we train or coach players to perform these tactical details in the best possible state should be the key target of all practitioners in the future.

Technical coaches, performance staff, medical practitioners and directors within the game will enjoy the content of this book and be able to integrate many components of it into their daily coaching or educational roles. Maximising the holistic link between the technical, tactical and physical details of the game has not only led to increased technology, analysis and specific personnel utilised within the game from a performance aspect, but additionally has ensured player injury is minimised. This book perfectly blends the research and development with practical, integrated coaching detail and provides a great coaching resource for all individuals wanting to develop their knowledge of the game.

Steve McClaren

Assistant Head Coach of Manchester United FC

Former Head Coach of Middlesbrough FC, England National Team, FC Twente, VfL Wolsburg, Newcastle United FC

FIFA Technical Advisor

PREFACE

Throughout the last few decades, the sporting landscape has seen many changes, notably the inclusion and professionalization of sport science and coaching. With football being the most participated and viewed sport throughout the world, the financial revenue generated within the game has led to significant demand and popularity for football science–based research. Not only has this research led to the improvement in player development, performance and further analysis over time, but it has also led to the development of new theories and methodology across all elements of the game. As a result of various investigations into training methodology, nutrition, psychology, testing and monitoring of players, head coaches, performance coaches and technical support staff are able to justify working practices with greater efficiency. Bringing together some of the fundamental aspects of football science and performance coaching within this book, I feel it is possible to engage all individuals with a thirst to evolve on a practical, or academic, level. The primary aim of this book is to provide a unique blend of modern football-specific research trends with innovative coaching theory and methodologies implemented at the elite level. Over time, many individuals within the game have questioned the implementation of sport or football science; however, as the players’ ever-growing educational level of sport science, and their own understanding of what is required to prepare, perform and recover, has grown substantially over the past decade, being able to justify decisions, interventions and methods to enhance player development has never been greater. As a technical or performance coach, sport scientist or medical staff member, evolution through growth mindset is vital in order to remain ahead of the competition. The flow of the book is based on a holistic approach to coaching science with a very applied and scientific overview of many practically linked, justified developmental training areas of football.

Having worked across many clubs, countries, continents and levels of the game from youth academy to elite UEFA Champions League and International level, within various high-pressure roles over a sustained period of time, I am delighted to bring together an incredible group of collaborators, highlighting the excellent football science work performed across these multidimensional but practically linked areas. Harnessing the academic and research side of the game and directly underpinning it with a successful and high-level practice-based approach is exactly what this book was constructed for.

I hope you enjoy reading it as much as I enjoyed the development of the project.

Also thank you to the excellent contributors for their time and effort in bringing the book to life in a very applied way.

Dr. Adam Owen, (PhD, MPhil, BSc, HONS)

UEFA Professional Coaching Licence

@adamowen1980

INTRODUCTION: APPLYING SCIENCE IN COACHING

When discussing the roles of coaching, performance or medical practitioners within football, it is possible to generally define the process across three main focus areas: PREPARE – PERFORM – RECOVER. As a result, one of this book’s priorities was to take the readers through interesting and modern training sections, highlighting the novel coaching approaches researched and used throughout the footballing world and delivered by some of the most innovative leaders in their specific areas of expertise surrounding performance coaching and football science.

Before diving into the first section, the cultural and societal impacts of football have been stressed alongside the game’s progression from its origin to the now globally unrecognizable sport loved by millions of fans. Within this introduction, the focus was to expose the reader to the sporting evolution of the game and how the financial strength of its attraction has not only professionalized football to a higher level, but how it has driven a sporting media explosion around the world. This section not only covers the game’s colossal socio-cultural development, but correspondingly how the changes have influenced the player development process along the way.

The reader then moves into the first key segment of the book, PREPARE. It is here that all individuals involved within the game – be they fans, players, coaches or performance practitioners – should understand the actual processes involved with the preparation of football athletes from a physiological, technical, tactical and psychological perspective. Furthermore, understanding the actual demands imposed on the players both within the training environment and competitive match-play is something that is of paramount importance to adequately PREPARE to PERFORM. The PREPARE section will investigate and cover the game demands in significant detail, revealing difference across both male and female game aspects while exploring further the hormonal and biochemical outcomes associated with high-level football performance. Having attended to the foundations and targets of what is required to PERFORM and the demands endured by players physically, the book moves into the psychological and mental skill developmental areas from a preparation perspective.

Described by many within the game as one of the most untapped, or under-utilised, areas of sporting performance, especially football, how leading practitioners in this specific area are researching, investigating and subsequently preparing their players across the world is fundamental to the reader in order to enhance their knowledge and practical capability thereafter. Bringing a unique look at psychological training intervention to maximise the development of creative players is something that all coaches, irrespective of their specialist area, crave within the game. The PERFORM section suggests in great detail not only how future talent is developed from a creative mind perspective, but also how incorporating visual perception and specific cognitive behaviour may identify the next generation of elite-level players and enable better coaching processes. From a PREPARE perspective, the PERFORM section includes a chapter on an extremely hot topic: long-term athletic development. Within all sporting contexts, especially within current elite football settings, never has there been such an investment into academy-based structures and talent management or identification. By presenting an improved insight into maximising skill development while embedding a long-term athletic development process within the talent phase of the player pathway, the book provides a modern and successful working process in this key area.

Having gained an insight into the preparation of players through a broad but modern, innovative spectrum, moving towards the second key section of the book, PERFORM builds on the PREPARE foundations already discussed. This segment highlights and exposes exactly what it takes to PERFORM at the top level of the game and how practitioners or coaches can provide the platform from which to progress the performance level of the players. Gaining a better or complete understanding of player capability through testing and monitoring in order to maximise performance, manage health and wellbeing, as well as stimulating enhancement through specific adaptation training is covered in this section of the book. Exposing the readers to the areas of training load management and invisible monitoring will provide a detailed overview of what coaches or performance practitioners can do to ensure their players remain in the best state to optimise performance, while at the same time reducing the injury risk to players. Chapters in the PERFORM section cover key topics that are fundamental to the development and management of players in a ‘high-performance’ environment. This section also introduces how artificial intelligence (AI) and data science in the football world can assist the ever-growing data management processes used by industry specialists. Describing the monitoring and assessment tools used within the game on a daily basis, plus the use of AI in decision-making aspects, the next section, and arguably one of the most important factors when it comes in the form of preparing to PERFORM, is training methodology. As a result of many contemporary research studies investigating performance markers and injury rates in elite sport, it is compelling to suggest that if the daily training content is poorly managed through an insufficient methodological approach, inadequate training session design or underconditioned players, then not only subsequent poor performance prevails, but also significant rates of injury. In order for both individuals and teams to reproduce a high-performance level and PERFORM continually through regular and congested periods each week for multiple seasons across a career, significant cohesive elements must align.

Individuals involved with the development of football players (coaches or support staff) have seen the understanding, progression and implementation of strength and conditioning, speed development and high-intensity football–specific endurance training exponentially over the last decade. Furthermore, developing their knowledge of where these components fit within the methodology of training, how to maximise specific training games in the weekly microcycle program, as well as periodising a training phase or understanding the benefits of tapering strategies in assisting their players to arrive on a match day in optimal condition may be of equal or more importance. Optimising the physical profile and status of players is only a part of the performance target, as from a coaching, performance and practitioners’ viewpoint, where the physical outcomes fit into the tactical and technical development of the player or team as a whole is fundamental to performance progression. The end of this PERFORM section is dedicated to the intricacies of monitoring the technical and tactical loads across the training week and further exposure to the tactical strategies used within the game at the elite level. This section was developed with the thought of providing a clearer view for how the tactical elements of the game may enhance practitioners’ decision making and strategy when it comes to designing specific multifunctional training sessions or drills to fit a specific game model or tactical plan.

The last section of the book is RECOVER. This part of the book outlines in greater depth the nutritional requirements of the sporting demands in order to maximise performance and PREPARE, PERFORM and RECOVER the players. This section highlights in a very practical way key nutritional theories and interventional strategies that are currently used at the very top level of play, while detailing the importance nutrition plays across all aspects of performance coaching. Optimizing the fuelling and recovery of training and competitive match-play is of great significance if players are to ever reach the performance goals set. The impact of nutrition on physical exertion, psychological decision-making processes while recovering the body between training and competitive match-play, emphasise its fundamental role as a key concept of football science. As nutrition is covered within the RECOVER section, it is vital that all individuals within the sporting world have a sound understanding concerning specific recovery modalities available to football athletes and how the research concerning this area can be used to maximise the efficiency and recovery of players.

As the book takes the readers through this latter section focused on elements of the game that fall under the RECOVER theme, based on the exponential growth of fixture demand imposed on players, the subject understood as fixture congestion is currently under the microscope and debated not only within clubs themselves, but very prominently discussed by technical staff members within the media. Fixture demand is becoming a fundamental aspect of elite-level football and a topic that, as a result, requires clear strategies to not only develop robustness in players, but also to navigate a squad through the demands faced. Based on new research findings in this area, it is vitally important to understand the physiology and biochemical aspects that come as a result of fixture congestive periods. Provision of recent research and focused areas to consider when faced with periods of fixture congestion in football are included here. The very last chapter within the RECOVER section of the book addresses the incidence and rehabilitation of injury in the football world and research supporting these topics. In addition to recovery from injury phases, this part of the book covers the area known as the return to play period, which includes football-specific rehabilitation processes that focus on all key stakeholders involved with this process, understanding the need to return the players safely to full training and competitive match-play while reducing the risk of re-injury.

CHAPTER 1

THE WORLD THROUGH FOOTBALL

Dr. Jožef Križaj

Modern football is rapidly evolving in all components of the game. According to the literature in this area, continued evolution of tactical demands, such as increased high-speed and intense pressure and counter-pressing in terms of ball recovery techniques, require players to have improved physiological, physical and general motor skills than previous years (Križaj et al., 2019). It is common knowledge that football is now played at a faster pace, with many more high-intensity periods during the game (Mohr et al., 2003). Within the English Premier League, for example, high-intensity running distance increased by 30% and action frequency by 50% in the time period from 2006 to 2013 (Barnes et al., 2014). Research has also contributed to the knowledge that high-speed running distinctly varies between playing levels (Bangsbo, 2014).

The main focus for any type of coaching is to provide the best possible platform for players to develop to the best of their ability, which subsequently leads to the best possible planning and preparation of training content ensuring they grow with the modern and innovative approaches within the game. The complex nature of football in terms of motor, technical skills and tactical abilities – psychosocial alongside cognitive skills – places a huge requirement of a strategic and multi-dimensional approach to planning and the training session design phase. Throughout the season, football coaches and performance practitioners are constantly searching for answers in justification of what to train, when to train and how to train in terms of weekly tapering strategies and periodised training programmes. When it comes to providing the answer to these questions, it is imperative that a holistical approach is taken and digested to make the best decisions for performance development. When discussing a holistic approach within the game and maximising performance as a coach, medical or performance practitioner, it is necessary to continually expand the understanding of the game using ‘football science’ as a way of making better decisions, justifications and improving expertise.

picture alliance/dpa | Lino Mirgeler

Due to the aforementioned complexity of football, the scientific monitoring of the game should incorporate findings from both the natural and social sciences. As a coach, it may be worthwhile to study research findings from the fields of sports training (physical and physiological diagnostics, physical training and conditioning), sports medicine (injury prevention and rehabilitation), motor learning, methodology (methods of football training in relation to tactics and technique), methods of match analysis, sports psychology, sports sociology, game and training demands specific to women’s football, youth and talent development. An overview of the main research findings in each focus area would enable coaches to provide an enhanced training session design to bring the overall training and playing ability to a higher performance level. The point is to put various pieces of information together like a puzzle in order to generate a meaningful and manageable systematisation of the most important developmental and progressive cornerstones of football.

Moreover, applied scientific research in the area of football science provides reliable data and identifies the important factors influencing performance levels. Scientifically sound and justifiable training strategies in football are essential for the continued development of match performance, but integration of the scientific research must be understood on a practical level to be of use. Simply producing a vast amount of data from different diagnostic areas in football can confuse coaches and have no impact on the coaching process. The research data should present the core areas of performance in a simple manner. As you will read throughout this book, applied scientific theory is important for player development and the creation of successful and modern training strategies. In almost all cases, the creation of a meaningful football training strategy requires a hybrid approach with broad and specific knowledge of all areas.

FOOTBALL – JUST A SIMPLE GAME?

From a socioeconomic perspective, modern football is a mega-media event due to it being one of the most profitable global sports markets, with finance and money the main drivers in the management process of the game at the elite or professional level. Transfer fees, player salaries as well as broadcasting rights for matches are constantly increasing. In this context, it is clear that global football could not develop independently without the overall social context of modern society. The multidimensional construct of sport, in our case football, is shaped, changed and reshaped by its relationship with society (Heinemann, 1983).

Today’s professional football in all its manifestations has a much more complex structure than the simple basic idea of the game. Modern football is a multidimensional construct, composed not only sociologically but also politically, economically and legally in very different ways. These factors have had and continue to significantly impact on the popular team sport, resulting in the fact that football is in a constant process of transformation due to these internal and external factors.

picture alliance/dpa/AFP/Pool | Ina Fassbender

As a result, it is not surprising that modern football has undergone many changes through its historical development. Rule changes can be observed during the evolution of the game, such as the modern offside rule and the back-pass rule, etc. Broadcasting technology (digital technology) and the sports broadcasting market have significantly changed since the mid-1990s, kickstarting the globalisation process of sports marketing. Nowadays, social media platforms increase the relationship between football players, clubs and fans while stimulating modern and innovative opportunities for revenue. In addition, there are improvements in technical support equipment for the officiating and conduct of football such as goal-line technology and video assistant referee systems.

picture-alliance /dpa/dpaweb|Tobias Heyer

Figure 1 Edgar Davids became one of the first and most high-profile Bosman transfers when moving from Ajax to AC Milan

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It is vitally important to understand from an external perspective where the legal changes within the game have significantly changed the face of football. The infamous Bosman ruling changed the conditions for player transfers between clubs, which fundamentally changed the contractual relationship between players and football clubs in Europe (free transfer at the end of the professional contract period). The Bosman ruling was, and still remains, one of the most important factors for the increase of football migration within the European continent. It appears that ‘push-pull’ factors in the form of better economic and social conditions (Magee and Sudgen, 2002; Lee, 2010) are mainly responsible for the migration of football players.

In this context, Maguire (2009) explains how modern sport is embedded in global networks of interdependent chains consisting of global flows and unequal (economic) power relations. Migration to a foreign (richer) football club can be described as a successful step in a player’s career. The transnational mobility of football players appears to be ongoing processes based on their own achievements and the aforementioned unequal power relations between the local place of origin and the international place abroad (Engh and Agergaard, 2015). In this context, Poli (2010) characterises international football migration not only as the creation of economic opportunities but also as a process inextricably linked to the biographies (qualities) of individual players. In general, football migration can be considered as an essential part of the globalisation processes in the sports industry (Taylor, 2007).

It can be suggested that the basic organisational form and structure of football in today’s modern society is subject to the constant influence of this society, and all technological, political, economic and legal developments can be considered a source of social change in the globalised field of football.

picture alliance/dpa | Omar Zoheiry

SOCIO-CULTURAL FACTORS ON PLAYER DEVELOPMENT

Following the general findings outlined earlier about the influence of society on the game, the question arises how socio-cultural or environmental factors influence the development of the individual football player. Many young players have the vision and desire to play at the highest level possible, but talent alone is certainly not enough to become a professional footballer. In this particular case, a major dilemma can arise for coaches: is the young player’s goal too high? Maybe, but if not, what can be done to move forward and make that desire a reality?

Maybe the young footballer is lucky enough to be in the right place at the right time, and a scout from the right club where that player fits the profile takes notice. But to be honest, that’s the best-case scenario, and it rarely happens. There is still no magic formula to becoming a professional footballer, with only a small percentage of young players selected to play at the highest level possible. Luck cannot be planned, but it is possible to identify the factors that lead to a successful football career.

Coutinho et al., (2016) claim that the development of a player in terms of their football career is a complex process that is difficult to explain due to the large number of influential factors. Forming a meaningful master plan for player development requires a holistic approach with a broad understanding of all these possible influencing factors. This is where the discussion about the right methodological learning approach for talent development begins, which, of course, is not always easy to define. Ultimately, not forgetting that coaches and practitioners are always dealing with individuals who have their own and specific predisposition (talent) for a particular sport. At the beginning of the talent development process, no one knows which methodological approach will fit the specific predisposition of an individual sports talent to develop the individual talent in the best possible way.

In this context, it should be noted that observation of the player on the field (scouting) in combination with functional diagnostics may not be sufficient to identify all influencing factors with regard to further player development. The main goal of physical and physiological diagnostics by measuring basic motor skills, such as strength, endurance, coordination, speed and agility, is to obtain some information about the specific performance profile of the individual. Feichtinger and Höner (2014) claim that social circumstances should also be considered when assessing a player. This statement is quite logical and understandable. Results of physical and physiological partial diagnostics of strength, endurance, coordination, speed and agility performances are always an expression of a certain reaction to a certain physiological task. The information obtained from diagnostics does not fully represent the performance level of football players in the overall context. This explains why football coaches often do not rely purely on diagnostics (science) in selection processes, but rely primarily on their coaching experience and a ‘good eye’ for perspective football players.

However, the level of performance in football is determined by many influencing variables. The process of player and talent development should include physical, physiological, sociological and psychological aspects, as the performance level of a young football player is influenced by all these aspects (Williams and Reilly, 2000; Zuber et al., 2016). For example, Gagné (2010), in his theoretical model, ‘Differentiated Model of Giftedness and Talent (DMGT 2.0 framework)’, defines social influences as ‘environmental catalysts’ that have a significant impact on an individual at both the macro- and micro-theoretical levels.

Figure 2 Adapted from Gagné (2010) theory ‘Differentiated Model of Giftedness and Talent (DMGT)

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The development of a football player seems to be a comprehensive process, however, during their developmental stages, the player learns not only motor and tactical skills but also socio-psychological skills that are important for successful interaction with their teammates on the field. In addition, they are also constantly learning behavioural strategies in their relationships with teammates, coaches and parents during daily life and leisure time (Križaj and Doupona, 2017). From a sociological perspective in relation to social learning and development, Coakley (2015) calls this environmental influence the ‘internalisation model’, which sheds light on the importance of these factors during a player’s developmental process.

To conclude, the development of a football player is a multidimensional and interdisciplinary process that requires the coordination and promotion of the various technical, tactical, physical, mental and socio-cultural skills of the individual.

From a sociological point of view, it could be said that the explanation of success in football cannot be based only on the notion of talent and individual physical abilities. It seems that social forces shape lives (Collero, 2013) and, consequently, level of performance, so it’s vitally important to grasp this notion for all practitioners within the game as a starting point when working with a group of individuals.

Coaches, performance practitioners and key medical staff in professional football should consider the socio-cultural and psycho-social background of each footballer to facilitate a high level of performance and working relationship. Such an assessment method would also significantly complement scouting and applied diagnostics by providing a holistic overview of a player and create ‘conditions for success’ in football player development (Križaj et al., 2016).

COACHING CONSIDERATIONS

•Applied scientific research in football provides reliable data and identifies the important factors that influence performance levels.

•Scientifically sound and justifiable training strategies in football are essential for the continuous development of match performance.

•Professional football, in all its manifestations, has a much more complex structure than the simple basic idea of the game.

•The basic organisational form and structure of football in today’s modern society is subject to the constant influence of that society, and all technological, political, economic and legal developments can be seen as a source of social change in the globalised field of football.

•The development of a player in terms of their football career is a complex process under the influence of various off- and on-pitch factors.

•The process of player and talent development should include physical, physiological, sociological and psychological aspects.

REFERENCES

To view the references for

chapter 1

, scan the QR code.

PREPARE

Football Demands – Ready or Not?

CHAPTER 2

DEMANDS OF THE GAME

Dr. Nikolaos Koundourakis | Dr. Adam Owen

Interest in the physiology of football and the competing players has grown exponentially throughout the last decade; however, the integration of physiology within football has been evident since the early 1970s (Reilly and Thomas, 1976). Subsequently, this key integration has significantly contributed to more understanding of football training, competition and the overall performance through the decoding and breakdown of the sports influence on the function and structure of the player’s body. As a result, the key identification and determinants of football performance have been created, contextually providing great insights into training optimisation, injury reduction and comprehending optimal performance.

Understanding the demands imposed on players through training and competitive match play, discussed later in this chapter, will hopefully enable a key insight into where football science and performance components evolution begins. This chapter profiles the specific energy demands of match play, the requirements of players physiological characteristics, while reviewing competitive contextual factors that affect performance demands and subsequent outcomes.

picture alliance/dpa | Angelos Tzortzinis

FOOTBALL CHARACTERISTICS AND GAME DEMANDS

Football as a sporting contest is characterised by alternating or intermittent bouts of work and recovery across various intensities and speeds, and is defined as a team sport of mixed aerobic and anaerobic activities (Stølen et al., 2005). During match play, players are required to execute random movement patterns of a multifaceted nature including explosive, maximal and near-maximal activities in multidirectional and linear natures (Di Mascio et al., 2015). These specific high-powered and exerting movements are also frequently interspersed with low-intensity jogging, walking, shuffling and standing actions. As highlighted from research surrounding the time-motion analysis of football athletes, activities occur across varied durations within the 90-plus minutes of match play, but are influenced by an array of factors, such as environment, opposing players, tactical requirements, technical and psychological capacity. Match play induces many complex physiological demands that highly tax all three energy systems: aerobic, lactic and alactic anaerobic (Figure 1) (Dolci et al., 2020). Due to the well-reported intermittent and acyclic nature of football, the in-play or dominant system at any given time point in a competitive game will depend upon the intensity of the performed activity (Figure 2). Typical characteristic football drills or activities performed in training sessions are generally dominated by each of the three energy systems and evolved as a result of the ‘Training Session Design’ phase, which will be discussed later in the PERFORM section of the book. Figures 3A–C highlight examples of specific drill types that elicit a predominantly different energy system when preparing the football athlete.

Figure 1 Energy demands of football. (Data adapted from Gastin et al. 2021 and Dold et al. 2020.)

Figure 2 Energy System interaction during exercise depending on activity intensity and its duration

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Figure 3A Football-specific drill dominated by each energy systems.

Figure 3A

shows players sprinting to receive the ball and shooting into the relative goal before walking to join the back of the group near the red box. On the coach’s command, players then sprint through the cones and compete in a 1v1 situation before jogging to the beginning (2 sets of 6 repetitions)

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Figure 3B

Game-based anaerobic lactic training:

2 vs 2 with goalkeepers, 90 seconds duration, 1/1 work-rest ratio, 4–8 repetitions, 1–2 blocks, 3 minutes rest between blocks, 3 touches, field dimensions 15 × 20 m

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Figure 3C

Game-based aerobic training:

6 vs 6 with goalkeepers, 5 minutes duration, 4–6 sets, 1–2 minutes rest between the sets, dimensions 30

×

40 m, free play

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Figure 4 Factors or constraints affecting competition energy expenditure

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Diving a little deeper into the energy demands of the game, it has been reported that during football match play, estimated energy expenditure can vary between the range of 1,200 and 1,500 kcal/game (Osgnach et al., 2010). However, higher mean values have been reported above 1,540 (Coelho et al., 2010; Shephard, 1992) and at times even >1,700 kcal/game (Stølen et al., 2005). These discrepancies are suggested to be as a result of several factors that affect match-play demands as shown in Figure 4. According to relevant literature in this key topic area, 80%–90% of competition is spent during low-to-moderate running speeds, whereas the remaining 10%–20% is covered within high-intensity running (HIR) and sprinting thresholds (Bloomfield et al., 2007). The provision of energy for this 80%–90% is predominantly derived from aerobic metabolism with this cost estimated via oxygen consumption (VO2) (Gastin et al., 2001). Since direct estimations of maximal oxygen consumption (VO2 max) require portable analysers, which has a limiting practicality during training or match play (Stølen et al., 2005), the employment of heart rate (HR) and core temperature metrics due to their clear association with VO2 have been used (Stølen et al., 2005). Further analysis into this area of research has suggested difficulties when assessing anaerobic energy provision of the 10%–20% covered in HIR and sprinting (Bloomfield et al., 2007) due to the employed methodologies for assessing match-play anaerobic contribution being limited to blood lactate (BLac) levels, or measurements of muscle phosphocreatine (PCr)1 concentration. Research in this area suggests muscle lactate values generally range between 2 and 12 mmol/L with ranges of PCr being between 30% and 60% of resting levels during competition (Bangsbo et al., 2007). However, both methodologies face practical difficulties and specific limitations (Figure 5) questioning their estimation capacity (Moxnes and Sandbakk, 2012).

Figure 5 Limitations of the employed methodology for anaerobic energy cost of match play

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PLAYER ANTHROMPOMETRY

Football players’ anthropometric, morphological as well as body compositional characteristics (e.g. somatotype type, age, height, weight, body fat and BMI) are believed to play a significant role in competitive performance output (Spehnjak et al., 2021). In general, football players have been found to have a somatotype2 (Figure 6) dominated by the mesomorphic category, with mean values of age, height, weight, BMI and body fat around 23–26.8 years (Bekris et al., 2021; Bloomfield et al., 2005; Joksimović et al., 2019); 1.73–1.83 m (Malone et al., 2018; Bloomfield et al., 2005); 71–83 kg (Slimani and Nikolaidis, 2019); of 22–24 (Cavia et al., 2019; Spehnjak et al., 2021); and 6.3%–11.9% (Slimani and Nikolaidis, 2019; Owen et al., 2018), respectively. Additionally, percentage fat values >15% have been reported within the literature for high-level individual players; however, the recommended levels for elite football players tend to be <10% (Cavia et al., 2019). This observed wide range of values has been found to be related to several parameters including player position, playing level, seasonal variations, different methodologies employed, and ethnicity (Figure 7). The importance of acknowledging this variability is that anthropometrical and body composition variables have been reported to be related to several factors related to success in competitions (Table 1).

Figure 6 Somatotype classifications

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Figure 7 Anthropometric characteristics per position in professional football players. GK: goalkeepers; DF: defenders; CD: central defenders; LD: lateral defenders; MD: midfielders; CM: central midfielders; LM: lateral midfielders; FR: forwards

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Table 1.

Anthropometry and body composition: implications for performance

ANTHROPOMETRY / BODY COMPOSITION

PERFORMANCE IMPLICATIONS

FACTORS RELATED TO ANTHROPOMETRY /BODY COMPOSITION INDICES

REFERENCES

Somatotype

Affecting Talent Selection Procedure

Talent Selection

Reilly et al., 2000

Height

Defining parameter of success in specific positions

Talent selection

Player level

Player position

Reilly et al., 2000,

Slimani and Nikolaidis, 2019

Joksimovic et al., 2019

Weight

Negative association with:

Work-rate profile

Energy expenditure

Player level

Player position

Reilly et al., 2000

Rienzi et al., 2000

BMI

Negative association with:

Work-rate profile

Muscle power outputs

Energy expenditure

Player level

Player position

Slimani and Nikolaidis, 2019

Body Fat

Negative association with:

Work-rate profile

Aerobic and anaerobic performance capacity,

Speed, power and agility performance,

Durability and physical dominance,

Competition-induced and residual fatigue levels

Energy expenditure

Player level

Player position

Ethnicity

Reilly et al., 2000

Slimani and Nikolaidis, 2019

Rienzi et al., 2000

CARDIOVASCULAR FITNESS AND AEROBIC CAPACITY

The significance of cardiovascular efficiency and aerobic capacity in football is highlighted based on the fact energy provision during match play is mainly produced by aerobic metabolism (Garcia-Tabar et al., 2019). Its importance is further highlighted by its reported association with various markers of aerobic capacity and the total, as well as high-intensity distance covered during match play, (Aquino et al., 2020) and the maintenance of competition high-intensity activities (Tomlin et al. 2001; Bradley, 2020; Altmann et al. 2018; 2020).

Linear associations with players’ capacity to limit lactate spikes through improved hydrogen buffering qualities (Jones et al., 2013) and subsequent energy-saving processes through glycogen sparing at given intensities link directly to improved aerobic function of footballers (Da Silva et al., 2008). Furthermore, the direct relationship between these improvements and accelerated recovery processes from training and games should not be underestimated by coaches working at the elite level of the game (Slimani and Nikolaidis, 2019). When assessing aerobic and cardiovascular function of athletes, VO2 max is generally accepted as the gold standard testing marker; VO2 max is defined as the highest work rate at which oxygen can be taken up and used by the body during maximum exercise (Stølen et al., 2005). In addition to this test, parameters such as the anaerobic threshold (ventilatory or lactate), running economy and the velocity at VO2 max (vVo2 max) are elicited as key markers of physical performance (Stølen et al., 2005). Regarding the latter, as described within the literature, VO2 max testing velocity (vVO2 max), apart from being employed as a measure of aerobic fitness, is also used in designing successful aerobic training programmes (Table 2 – Figures 8A, 8B, 8C, 8D) (Buchheit and Laursen, 2013).

In football, VO2 max values have been found to be within a mean range of 48–75 mL/kg/min (Schwesig et al., 2019; Slimani and Nikolaidis, 2019) with a proposed minimal threshold of ~60 mL/kg/min for elite level players (Helgerud et al., 2001). The observed variability in VO2 max is the result of several factors inclusive of the training stimulus, competitive phase of the season (Koundourakis et al. 2014), playing position (Boone et al., 2012) and the quality of player level (Bekris et al., 2021; Koundourakis et al., 2014) (Table 3). Although some evidence indicates variability per position, with midfielders generally shown to have higher levels of VO2 max (Sporis et al., 2009), recent data reveals that apart from the goalkeepers (i.e. lowest levels), no additional difference exists between outfield players (Modric et al., 2020). This suggestion is supported by the similar VO2 max levels observed in starters versus non-starters, suggesting the training session to be the most influential factor for VO2 max adaptations rather than accumulated competition time per se (Modric et al., 2020). Figure 9 highlights the importance of VO2 max for football players, and it shows how it is directly related to several factors enhancing performance during match play.

Table 2.

vVO

2

max association and training application

VELOCITY AT VO

2

MAX %

ACTIVITY TYPE

DURATION

90%–110%

Long-interval exercises

2–6 minutes high-intensity effort with passive recovery of 2–3 minutes

110%–130%

Short-interval exercises

10–60 seconds high-intensity effort with various work-rest ratios (2:1, 1:1, 1:0.5, 1:3)

130%–160%

Repeated sprint trainings

<10 seconds all-out efforts rest with recovery periods lasting generally less than 60 seconds and work-rest ratio of approximately 1:3

>160%

Sprint interval trainings

20–45 seconds all-out effort with 1–4 minutes passive recovery periods

Adapted from Riboli et al., 2021; Buchheit and Laursen, 2013.

A)

Game-based training for long-interval exercises:

4 vs 4 ball possession without goalkeepers, 3 minutes duration, 4–6 series, rest <2 minutes, field dimensions 20 × 30 m, 3 touch rule

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B)

Position-specific short-interval training:

Full-back (FB) starts dribbling and at the same time forward (FR) makes a very high intensity run over the manequinn where he receives a pass from FB. FB sprints on space receiving a pass near the corner from FR who makes a sprint towards the post receiving a cross from FB aiming to score. Immediately after the cross, FB sprints towards the 1 vs 1 area to defend while, after the attempt to score, FR receives a pass from the coach (C) and dribbles with maximal speed to the 1 v 1 area aiming to overpass FB and score. Two blocks of 8 repetitions of 20-second duration with 60 seconds rest (initially with jogging to the starting position)

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C)

Football-specific repeated sprint training:

Players work in couples, they sprint after C signals towards the mannequin, at mid distance where the C passes in one side and the player of this side finishes the action with a maximum of 3 touches while the other player is defending. The duration of each repetition is 4 seconds with approximately 20 seconds passive recovery periods. Players perform 2 blocks of 4 minutes each one (4 minutes each drill [drills A & B]), with field dimension 15 × 30 m. In drill A, players either jump over hurdles or perform 4 single leg jumps on rings. In drill B player perform a 6 m (3 m + 3 m) of a 45-degree change of direction and then sprint towards the mannequin

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D)

Football-specific sprint interval training:

Two groups of players compete for the highest scores. Players compete in couples for 20 seconds to score the highest possible goal numbers. With the signal of C, they sprint with the ball and, after passing the middle line in the shooting area, they shoot, then sprint back take another ball from the starting position and so on until time limit is reached. Players perform 1 block of 6–10 repetitions of all-out 20 second duration sprints, with 120 seconds rest

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Figure 8 vVO

2

max variations through football-specific drills

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Table 3.

Parameters related to VO

2

max variability in football

PARAMETER

VARIABILITY EFFECT

REFERENCE

Player Level

Higher VO

2

max at higher vs lower competitive level

Slimani and Nikolaidis 2019; Bekris et al., 2021; Koundourakis et al., 2014

Playing Position

Lower level at GK vs all outfield players

Slimani and Nikolaidis 2019; Bekris et al., 2021; Modric et al., 2020

Period of the season

Lower values at the beginning of the preseason

Values are increasing towards the mid-season

Increases are evident at the end of the season

Koundourakis et al., 2014

Koundourakis et al., 2014

Koundourakis et al., 2014

Figure 9 Cardiovascular fitness importance

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ANAEROBIC THRESHOLD AND RUNNING ECONOMY

Anaerobic threshold (AT) is defined as the highest exercise intensity presenting a balance between lactate production and clearance (Stølen et al., 2005). Its importance is based on the theory that players with better AT levels can maintain a higher average intensity, at higher velocity during match play (Helgerud, 1994) without the onset of BLac accumulation (Figure 10). AT has been suggested to be a more sensitive indicator of changes in aerobic training status versus VO2 max (Hoppe et al., 2013) due to the fact that there are periods where VO2 max is stable, AT values show significant variations (Clark et al., 2008). The AT cut-off point in football has been suggested to be around the running speed of ~4 m/s (14 km/h) situating itself around the 4 mmol/L lactate threshold (Foehrenbach et al., 1986). In football players, AT velocity value varies between 3.4 and 4.7 m/s (12–17 km/h) according to reports in this area (Chmura et al., 2015; Schewig et al., 2019). Discrepancies within the literature surrounding this topic revolve around research describing different player levels and position, periods of the season, substrate availability and environmental factors, as previously described (Schwesig et al., 2019).

Figure 10 Representation of aerobic and anaerobic metabolism contribution to performed activity based on AT values at different lactate thresholds

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As previously mentioned, running economy is another vital indicator of aerobic capacity. As a measure, it represents the aerobic energy cost to exercise at that current given submaximal velocity (Dolci et al., 2018). Several factors play a significant role in this monitoring method, such as different composition of muscle fibre type, predominant training type characteristics, genetic potential and capacity, and age of the football athlete (Santos-Silva et al., 2017a). It has been reported to be a very sensitive training or performance assessment marker, and to discriminate elite versus non-elite athletes even with similar VO2 max levels (Table 4). Research suggests that running economy values can be significantly altered with increases in lower body strength as a direct link between neuromuscular outcomes, and additionally, its value is partly limited during activities that involve changes of direction that are frequently performed at high effort in football (Dolci et al., 2018; 2021).

Table 4.

Factors affecting running economy levels

FACTORS AFFECTING RUNNING ECONOMY

Muscle fibre composition

Training characteristics

Change of direction within the performed activity

Genetic endowment

Age

Player level

Dolci et al., 2018, 2021; Santos-Silva et al., 2017a

STRENGTH AND POWER DEMANDS

Team sports, such as football, that encompass large intermittent physical demands rely significantly on player strength and power capabilities because those are essential factors influencing competition success (Kobal et al., 2017). Research in this area has reported the association of strength and power levels with the most decisive skills or match-winning movements during match play (Hammami et al., 2017). These movements include jumping to head the ball, explosive jumping to make a save, attempting to sprint past a defender or perform an explosive recovery run to perform a defensive action. Diving deeper into the question of strength and power, Brewer, (2017) suggests that the most common method for the determination of this physical attribute in football is using the 1–5 Repetition Maximum (RM) back squat or trap bar deadlift, use of isokinetic dynamometry or explosive jump test capacity (these methods and exercises are discussed in further detail in chapter 15, Strength and Conditioning for Football).

Repetition maximum (RM) and isokinetic testing is a very well researched, well-documented and widespread methodology to assess strength metrics in team sports. The 1–5RM assessment is one of the most commonly discussed tests employed in football through the half-squat (Wisløff et al., 2004), with reported values ranging significantly between cohorts assessed (Table 5). Within and among practitioners, there seems to be a proposed rule of being necessary to back squat or deadlift at least 1.5–2 × body weight for 1RM, which is commonly referred to in the strength and conditioning literature (Haff and Nimphius, 2012) as sufficient for player robustness and high-performance levels.

Moving to describe isokinetic strength testing within this section, it should be noted that significant amounts of research and literature promote its formal use within high-performance sports as a monitoring method to assess strength, injury risk assessment, injury-reduction tasks and techniques, alongside both identification of bilateral asymmetries and strength ratio imbalances (Sliwowski et al., 2017). Although its practical application has been questioned in football due to the strength association of its use with functional performance measures, the significance of research in this area from both the conventional3 and the functional4 hamstring-to-quadriceps (H/Q) ratios to identify injury risks cannot be disputed. Moreover, in recent research, interest has emerged for the mixed eccentric 30° H/concentric 240° Q due to the observations showing higher prognostic values for football injury, especially in players with untreated imbalances (Croisier et al., 2008). The main characteristics of 1 RM and isokinetic testing are described in Tables 5, 6 and 7.

Table 5.

1 Repetition maximum (1RM) characteristics

1RM

CHARACTERISTICS/FINDINGS

REFERENCE

Definition

•Maximal weight an individual can lift for only one repetition with correct technique through a full range of motion used

Rontu et al., 2010

Range of reported values in football (half-squat)

•Absolute values: 100–215 kg

•Relative values: 1.66 kg lifted/kg body weight to 1.96 kg lifted/kg body weight

Rønnestad et al., 2008;

Andersen et al., 2018;

Style et al., 2016;

Rodríguez-Rosell, 2017

Contextual factors

•Player level: lowest absolute in non-elite vs elite players

•Training age: result of training adaptation

•Period of the season: result of training adaptation

•Different equipment used: affect accuracy of the results

•Proper execution technique: affecting testing outcome

Requena et al., 2009;

Slimani and Nikolaidis, 2019;

Rønnestad et al., 2016;

Grgic et al., 2020;

Rodríguez-Rosell, 2017

Table 6.

Isokinetic testing main characteristics

KEY POINTS OF ISOKINETIC TESTING

PARAMETERS

COMMENTS /REFERENCES

Type of contraction assessed

Concentric

Eccentric

During concentric contractions, the force values decrease with increasing angular velocities (Gür et al., 1999) – a parameter that affects the functional H/Q ratio

During eccentric contractions, the force values is either the same or even increased with increasing angular velocity (Baroni et al., 2020) – a parameter that affects the functional H/Q ratio

Common examine measures

Peak torque

Average torque

Total work

Side-to-side asymmetry

H/Q conventional and functional ratios

Defined as the maximum torque generated at a single point of the entire range of motion among all test repetition either of concentric or eccentric actions (Osawa et al., 2018)

Refers to the average of the highest values obtained during testing (Sliwowski et al., 2017)

Defined as where the sum of repetitions the athlete performed during the test occurred, and is mainly employed for the measurements of muscle endurance capacity of the player (Sliwowski et al., 2017; 2020)

Asymmetries greater than 15% may demonstrate a strength imbalance and increased injury risk (Sliwowski et al., 2017; 2020).

H/Q conventional (concentric H/concentric Q; cut-off values 0.6) and functional ratios (eccentric H/concentric Q; cut-off values 1.0) (Sliwowski et al., 2017)

Testing velocities spectrum

30°, 60°, 120°, 180, °320°, 360°

Slow speeds are considered ‘strength speeds’ (60º/sec to 120º/sec) and fast speeds (180º/sec to >300º/sec) are considered ‘endurance speeds’ (Freund et al., 2016)

Lower speeds are better indicators of muscle deficits while higher speeds better reflect sport-specific functional demands (Eustace et al., 2017)

Torque measurement unit

(Newtons), torque (Newton/Meters), range of movement (degrees), angular velocity (degrees per second) and duration (seconds) of the muscle action

Absolute values in Newtons and Newtons per min, Body-weight normalised in Nm/kg

Nm/kg takes into consideration the anthropometric characteristics of the players even if marked discrepancies in body size are evident, allowing more accurate comparisons (Delvaux et al., 2020)

Reference values

Concentric Q and H: Great variability is observed per velocity. Lower angular speed results in higher values in concentric actions while those do not show significant variations in eccentric actions

Eccentric Q and H: The isokinetic eccentric torque-velocity curve in humans appears to remain essentially constant

Example in same players:

Peak torque concentric Q and H at 60°: 280 and 160 N m

Peak torque concentric Q and H at 300°: 155 and 125 N/m

Example range at 60° from the literature: 256–419 N/m

Concentric Q and H at 60°: 260 N/m and 160 N/m

Example in same players:

Peak torque eccentric Q and H at 30°: 293 N/m and 174 N/m

Peak torque concentric Q and H at 300°: 299 N/m and 185 N/m

(Nunes et al., 2018; Dvir, 2004)

Deficits

Are mainly eccentric in nature

The majority of the deficits are observed in eccentric-related actions although these findings are not universal (Sliwowski et al., 2020; Fousekis et al. 2010)

Bilateral asymmetries

Were observed at lower speeds 60 vs higher speeds

Higher accuracy when examining asymmetry in lower speeds (Menzel et al., 2013)

H/Q ratio cut-off values

H/Q conventional

H/Q functional

H/Q conventional and H/Q functional at different velocities

Concentric values of both hamstring and quadriceps ratio

Ratio of eccentric hamstring value to concentric value

Modification is needed according to different angular velocities at slow to intermediate angular velocities test (12–180°·s−1). The H/Q conventional ratio score should be close to the typical reference landmark of 60%; at fast angular velocities (240–360°·s−1) it should be close to 70%–80% (Baroni et al., 2020).

The suggested 100% is never reached for slow angular velocities. The H/Q functional ratio score should be around 80% or within the range of 100%–130% at 60°·s−1 and tests performed at intermediate to fast angular velocities (120–300°·s−1) respectively, and near or above 130% in tests with mixed angular velocities (eccentric hamstring < concentric quadriceps) (Baroni et al., 2020)

Table 7.

Contextual factors affecting isokinetic testing outcome

PLAYER POSITION

Goalkeepers (GK) and central midfielders (CM)

GK vs central defenders (CD) and external midfielders (EM)

GK vs CD, CM and EM

GK and centre-backs (CB)

GK and forwards (FW)

Players in these two positions possess lower strength levels of extensors and flexors compared with other field positions

Total work of quadricep for GK were observed lower than for CD and EM

Total work of hamstring for GK were lower vs CD, CM and EM

Players in these two positions have higher hamstring strength for both dominant and non-dominant legs than players in almost all field positions

Players in these two positions have higher quadriceps strength (Carvalho and Cabri 2007; Sliwowski et al., 2017)

Competition level

Higher levels of competitions are associated with better isokinetic assessments (Sliwowski et al., 2017; 2020)

Player experience (training age)

Variability with age has been reported and players with a higher football training age have better isokinetic strength values (Fousekis et al., 2010)

Training-induced adaptations

Content/type of training programmes followed by the players (Silva et al., 2015)

Period of the season testing has been performed

Early season lower values have been reported (Sliwowski et al., 2017)

Injury history

Affects its levels in a series of ways (Sliwowski et al., 2017).

Different equipment (dynamometer type)

Values from different equipment affects comparison accuracy (Sliwowski et al., 2017)

JUMPING POWER AND EXPLOSIVE ABILITY

The most common field tests for the determination of lower limb explosive power are squat jump (SJ) and countermovement jump (CMJ) (Koundourakis et al., 2014). The SJ assesses concentric leg-extensor power while CMJ includes the dynamic muscle action known as the stretch-shortening cycle (SSC)5, which is characterised by a rapid eccentric action followed by concentric muscle contraction, which is one of the most common muscle actions performed during human movements (Heishman et al., 2019). The significance of assessing both SJ and CMJ is well demonstrated and documented in football (Table 8). Apart from their apparent relationship with jumping actions, a linear relationship with sprinting capacity, acceleration, decelerations and changes of direction ability is also clear and evident (Hader et al., 2019). In addition, CMJ can serve well as an indicator of residual neuromuscular fatigue, with even further analysis provided through the single-leg test variation (slCMJ), which highlights or identifies bilateral asymmetries (Heishman et al., 2019; Hader et al., 2019). From the SJ and CMJ values, players’ SSC ability can be assessed (Suchomel et al., 2016) through calculating factors such as the pre-stretch augmentation-percentage (PSA [%]), the eccentric utilisation ratio (EUR) and reactive strength index (RSI),6