Science and Football II

Jan Clarys, Thomas Reilly, A. Stibbe

• Publisher: Taylor & Francis
• eBook ISBN:
  9781135827694
• Year: 2003

This book includes all the papers presented at a second World Congress of Science and Football (Liverpool 1987) (Eindhoven).

PART ONE

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Science and Football:
Opening Address

SCIENCE AND FOOTBALL : AN INTRODUCTION

T. REILLY

Centre for Sport and Exercise Sciences, The Liverpool Polytechnic,
Liverpool, England.

1 Introduction

This overview of science and football provides an opportunity of articulating the philosophy of the Congress of Science and Football, and of forging a link between the First World Congress at Liverpool in 1987 and the present event. It presents also a personal perspective of achievements so far in research applied to football in its various codes. The Congress is geared towards representatives of all the football codes — American, Australian Rules, Gaelic, Rugby League and Union, and soccer. Indeed the inaugural Congress at Liverpool in 1987 was the occasion when formal representatives from all the football codes came together for the very first time.

The audience at such a meeting is inevitably varied in background. The sprinkling of academics and practitioners includes scientists, statisticians, teachers, medical, paramedical and engineering expertise on the one hand and managers, coaches, trainers, players, game officials and supporters on the other. A major objective is to effect a bridge between theorists and practitioners so that there is dialogue and debate between them.

This formula for cross-fertilisation is endorsed by the International Council for Sport, Science and Physical Education and also the Vorld Commission of Sports Biomechanics. Their programme of scientific conferences allied to specific sports started with swimming and its inaugural meeting in Brussels in 1970. Meetings are held every four years, the sixth symposium for biomechanics and medicine in swimming having been held at Liverpool in 1990. The most recent addition to the calendar was the First World Scientific Conference of Golf, held prior to the 1990 British Open at St. Andrews. In the normal schedule of events the Third World Congress of Science and Football will take place in 1995.

Football, in one or other of its forms, is unique in its universal appeal. It can give national identity an expression for both developing countries, such as Cameroun in its 1990 World Cup performances, and space-age nations. It reflects also common themes and origins among the football games, rugby as legend has it having sprung from a foul play in soccer and then developing into separate codes and Australian Rules evolving from the version of Gaelic football imported by Irish immigrants. Hany skills and tactics are common to two or more of the football codes and there are many instances of top players switching to alternative football codes without undue difficulty.

Before proceeding to a scientific description of football, I wish to underline the important role that football has in contemporary culture. I can do so by referring to observations at a qualifying match for the 1970 World Cup for soccer between Nigeria and Cameroun. The game was held in Douala in ambient temperatures exceeding 30°C. At this time the Biafran War was still unresolved whilst civil disturbances were being crushed in the countries neighbouring on Cameroun. Yet life according to the conventions of competitive soccer went on; these have a logic which sometimes supercedes analysis.

2 Behaviour Analysis

The first hallmark of science is rigorous observation. This provides data which allow description of events in progress and ultimately some inferences that afford insight into the events being observed. This process is illustrated by some of our early observations on professional soccer on Herseyside.

Soccer practitioners are mainly concerned with performance. A scientific approach towards analysing the game can employ an ergonomics perspective as a broad thrust. This can operate on a number of fronts by studying:-

i) work-rate during matches;

ii) severity of training;

iii) fitness of players;

iv) psychological stress;

v) physical stress and injuries;

vi) daily energy expenditure

In this paper consideration is restricted to the performance aspects and the physiological investigations. The detailed findings have been reported elsewhere (Reilly, 1979; Reilly, 1986; Reilly, 1990).

In one of the first applications of motion analysis to professional soccer, the premise was that work-rate could be expressed in gross terms as total distance covered in a game, since this determines the energy expenditure. Obtaining work-rate profiles required careful observations of specific activities of individual players throughout a complete game. Co-operation with the club groundsman vas necessary to devise a grid of the pitch in 1 m bands and visual cues both on the pitch and alongside the sideline were used. The method of coding the type and intensity of behaviour onto a tape-recorder from a vantage point overlooking the half-way line was cross-checked using film analysis and stride characteristics of players. The work-rate profiles indicated the nature of game demands, implicated fitness requirements for play and generated the reference data for devising training programmes.

The main categories of activity were classed as jogging, cruising, sprinting, walking and moving backwards. On average there is a change in intensity every 6 s, a burst of effort every 30 s and an all-out sprint every 90 s. The overall distance covered, including that by the goalkeeper, is about 9 km, most of the activity being sub-maximal and aerobic. The distance covered in possession of the ball is about 2% of the total. So, put another way, if you merely

Fig. 1. Distance covered (m) for classes of activity in soccer.

watch the ball you miss 98% of the activity! This is evident on inspection of pie diagrams of the breakdown (Figure 1). Of course superimposed on this profile are the frequent accelerations, decelerations, angled runs, moving backwards and game-related actions such as jumping and tackling that add to the demands of match-play.

Average values may disguise differences between playing positions. In soccer, for example, the greatest distance is covered by midfield players, the least among outfield players by the centre-backs. The positional role may be reflected also in discrete activities e.g. the greater call on midfielders and strikers to sprint. Overall the game is essentially aerobic, as evidenced by the cruising and jogging profiles of players, the highest work-rate being associated with the highest V0 2 max. The specificity of demands on the defenders who spend a lot of time back-pedalling is noted. Similar profiles of other games can be built up so that appropriate training programmes can be formulated. Gaelic football, for example, is played on a pitch 40% longer than soccer or rugby but has 15 a-side. The profile of activity is very similar to soccer when one player is followed. Game-related activity accounts for 1.3% of the total work and in the main players are exercising submaximally with occasional sprints mostly “off the ball” (Figure 2).

Indeed when we look at the work-level in distance covered per minute, Australian Rules and soccer are the most demanding, Rugby Union and American Football the least (Figure 3). This is reflected in the values at top level of VO₂ max which show the games players

Fig. 2. Relative time spent in various categories of activity in four football codes.

Fig. 3. Work-rate in match-play for the various football codes.

that are highest in ft) 2 max. It is offset by the strength and muscle power needed for American football and Rugby League in particular (Figure 4).

The distance covered in various activities underlines this. Much of the striding and sprinting in Rugby Union, for example, is to support the player on the ball.

Time in activity categories related to total time shows that except for game-related activities the profiles for soccer, Australian Rules, Gaelic football and Rugby Union are comparable — mostly low-level aerobic exercise. The high game-related activity in Rugby is dictated by the time spent in scrummaging, an activity that is the subject of biomechanical and medical considerations.

Of course there are extreme anaerobic demands on all games, whether these are the jumping and timing skills of Australian Rules players or the sprints of the Rugby and American football games. These show that the activities in the game cannnot be directly extrapolated from isolated running. An example is seen in dribbling, which it is possible to simulate in laboratory conditions. The protocol required a player to dribble on the treadmill, with the ball being returned to him via a rebound box at a rate compatible with what is done in the game (Reilly and Ball, 1984).

The data showed that there is a linear increment in both oxygen consumption and blood lactate at each speed of dribbling. One of the implications is of course that it might be best for players to train with the ball. One of the contributing factors to the added energy cost is the change in stride rate, the best dribblers using the change in stride rate to deceive opponents.

Additional physiological costs are also evident when players move backwards or sideways. This is reflected both in oxygen consumption and perception of effort (Reilly and Bowen, 1984). It suggests also that these features need to be built into the training programme.

Fig. 4. Typical values of muscle strength (arbitrary scores based on strength data reported in the literature) and VO2 max of players at high levels of competition in the various football codes.

3 Training

It was possible to look at the training programme of First Division players using long-range radio telemetry (Reilly and Thomas, 1979). During training the elements may be classified into warm-up, calisthenics, fitness (weight-training or running), skills, drills, games; the programme started with warm-up and flexibility work, and fitness work. Most emphasis was placed on games either short-sided or full-sided simulations of match-play. The latter has allowed us to compare work-rate and heart rates during real play and calculate energy expenditure levels.

The heart rate data indicate that players work hardest during their games. When figures include goalkeepers, the average heart rate is 157 beats/min : otherwise the values are about 160 beats/min. It was estimated that on average outfield players operate at 75–80% V0₂ max, which is comparable with high standard marathon running. The calculation is achieved by obtaining HR-V0₂ max regression lines in the laboratory and both HR and work-rate in friendly matches.

It is common practice for coaches to use performance tests during training to monitor fitness. The argument is that they are more user-friendly than laboratory tests such as V0₂ max. Such tests tend to have poor reliability with professional players. This gets worse the longer the duration of the test. Players want to show improvement when it is important and so underperform on the first test.

4 Habitual Activity

The training of footballers is varied sensibly from day to day, showing a cycle of energy expenditure during the week. The mid-week peak is followed by a lowering in preparation for mid-week competition. This preparation is enhanced if the training is supplemented by a dietary programme.

Reilly and Thomas (1979) examined how professional players do expend their energy once outside their occupational context. They spend very little energy other than during training and playing. Most of their activity is sedentary or lying resting and so it appears justifiable to describe the professional footballer as “homo recumbans”.

The highest rate of energy expenditure is during competition and this leads to fatigue as reflected in a drop in work-rate in the second half of soccer. This is related to reduced energy stores in the form of gly...

Table of contents

• Cover
• Science and Football II
• Other TitIes Available
• Full Title
• Copyright
• Second World Congress of Science and Football
• Contents
• Preface
• Introduction
• PART ONE Science and Football: Opening Address
• PART TWO Physical Fitness Profiles of Footballers
• PART THREE Physiology of Training
• PART FOUR Physiology of Match-play
• PART FIVE Match Performance Analysis in Football
• PART SIX Match Analysis: World Cup Soccer 1990
• PART SEVEN Psychological Aspects of Soccer Skills
• PART EIGHT Paediatric Science and Football
• PART NINE Biomechanics
• PART TEN Medical Aspects of Football
• PART ELEVEN Managing and Coaching
• Index