The science of football

From bending balls and the ultimate shin pads to diet and the perfect excuse for goalies - it seems that science is involved in the beautiful game every bit as much as stressed managers and cheering fans

Science and football. Not - you might think - ideal partners, but in the midst of World-Cup fever, Laboratory News can reveal that to bend it like Beckham you need to rely on more than just a cracking right foot. So here is our run down of the best bits of science that could make all the difference if football is to really come home this year.

The potential of understanding the science behind the game is now gaining weight among the football fraternity – so much so that football science is big business, making an impact on everything from training regimes to ball design. Indeed, Sir Clive Woodward, director of football at Southampton, has become one of the first to recruit a club science advisor in the form of Dr Ken Bray – a ball bending expert and author of How to Score, a book that promises players an ‘unstoppable’ free kick. But more on bending later, right now we need to start at the beginning – the ball itself.

What a load of balls

The game of football generally flourished in England from around the 8th Century onwards. Games were normally violent and disorganised affairs with any number of players – the Millwall fans among you may argue that not much has changed, but in fact it was not uncommon for 1000 people to play in a single match. Something approaching the game we know today, with rules and regulations we might recognise, originated in the 19th century in English schools and universities.

The first purpose-made balls were simply pig or sheep bladders inflated by the payers and knotted at the end. It was the invention of a rubber bladder in 1862, along with a pump to inflate it, which meant that a round ball which retained its shape could be easily produced. Today, footballs are made from leather patches sewn together in a design based on the Buckminster ball – a design well known to science. The modern football is essentially a Bucky Ball consisting of 20 hexagonal and 12 pentagonal surfaces – when sewn together and inflated they make a near perfect sphere.

Once you have your near perfect sphere, you need to know how to kick it. Sounds simple enough. But of course – and this may come as a surprise to Sol Campbell - there is more to the game than randomly kicking a ball around a pitch. This is where the skill comes in, and, as it turns out, science has a prominent role in nurturing this skill.

Give ‘em the finger!

Some players just seem naturally gifted, and some work hard at their game to improve. But is there such a thing as a natural footballer? Could it really be genetic?

Research from the UK seems to suggest that good footballers could indeed have a genetic advantage. Dr John Manning from the University of Liverpool has published findings that suggest a link between the length of a footballer’s ring finger and their ability as a player. He measured the difference in length between the ring and index fingers of top players and found that elite player’s have longer ring fingers compared to their index fingers. Players found to be in this ‘long finger club’ include Bryan Robson, Sir Stanley Matthews and Gazza. Dr Manning offers an explanation for this unlikely linkage: “There is evidence that our fingers tell us how much of the male hormone testosterone we have been exposed to before birth. Early exposure to testosterone is important in males for the formation of the heart and in determining ability in spatial judgment.”

So it is possible that some players have a genetic predisposition for good spatial awareness, a vital skill for world-class footballers. Maybe this is why the tradition of shaking hands with the opposing team before a big game has grown up. They may claim its good sportsmanship but maybe, just maybe, it is in-depth scientific analysis of finger length. Although, readers beware, if you catch Gazza bragging about the size of his digit, it is unlikely he is referring to his football skills. Or his ring finger for that matter.

A genetically programmed footballer or not, the one thing they all need is rigorous training, and once again the coaches and trainers have looked to science for the answers.

Well fit

In the course of an average match a midfield player will run seven miles, so fitness is a must. But it is not only stamina that players need, but also power. In the 1960s scientists in the Soviet Union were tasked with turning their athletes into powerhouses and came up with plyometric training. This technique is now widely used in football training programs and is based on the fact that footballers tend to use their muscles in two different ways. Concentric contractions that shorten muscles and eccentric contractions that lengthen and hold them under tension.

Both these contractions are vital if footballers are to run, stop and jump in quick bursts. Plyometrics are designed to train a footballer to switch between the two very swiftly, and not only targets the muscles but also the nerve fibres controlling the muscles.

This alternating muscle usage may be good for winning games, but it bad for muscle energy stores. During the course of a match a footballer’s activity is adequate to empty leg muscles of most of their glycogen, and just six seconds of all-out sprinting can trim muscle glycogen by 15%.

This is where nutritional science can help out.

Isotonic or gin and tonic?

Diet plays a huge role in the performance of most sportsmen and women, and footballers are no different, as the Spurs team knows all too well.

Dr Barry Drust, programme leader of the Science and Football course at Liverpool John Moores University, told Laboratory News: “Science now plays an increasing role in professional football at the elite level, and a lot of this expertise is based on diet and nutrition.”

Carbohydrate is the key. In recent research carried out with an English football team, players consumed a glucose-containing sports drink during 10 of their games but swallowed only an artificially flavoured, coloured-water placebo during 10 other competitions. When the players used the glucose drink, the team conceded fewer goals and scored significantly more times, especially in the second half. When the placebo was ingested, players were less active and reduced their contacts with the ball by 20-50% during the final 30 minutes of their games.

Research suggests that 12-14 ounces of sports drink, which usually provides about 30 grams of carbohydrate, 10-15 minutes before a match begins, with the same amount at half-time, is ideal for a 90 minute match.

So that just leaves the traditional after match tipple. Alcohol, whether used to drown sorrows or boost a win, is a big no-no. Its diuretic properties mean that players will lose more fluid in urine than they can drink, and as they can lose up to seven pints of fluid during a match that is bad news for recovery. Damaged joints and muscles can’t be repaired as efficiently if the body is dehydrated, so the post-match tipple has to be isotonic – a delicate balance of energy and salts that enables swift re-hydration - rather than a gin and tonic – a delicate blend of spirit and mixer than enables swift inebriation. Even after all the advanced training and perfected diet, there is always room for a little tweaking, and once again science can help out.

A materials science company from the UK – d3o – has teamed up with sports wear specialists Sells to develop smart clothing that is both flexible and rigid. This means that goalkeeper’s gloves can flex when stretching to save that vital penalty but immediately stiffen when the ball strikes. This “intelligent” material gets its qualities because of the way the material works on a molecular level. The molecules are free flowing under normal circumstances as they have time to move over each other, allowing the material to be soft, flexible, and malleable. However upon impact, the molecules form temporary cross links with each other, transforming the material into a stiff state, in addition to absorbing the energy from the impact. As soon as the impact is over however, the molecules unlink, returning them to their original free flowing state.

The material has also been used to make shin pads that can reduce the amount of force transmitted to a player’s leg by up to 70%. Some say this means that Italian players will have fewer reasons to writhe around on the floor when an opposing player comes within 5 meters of them, while others have pointed out that even the ultimate shin pads can’t change the habits of a lifetime. Spin doctors and the perfect excuse

Many have wondered what must go through Beckham’s mind when he is lining up for one of his famous free kicks. Defensive walls often mean that he has to bend the ball to be in with a chance of scoring.

So could it be that he is pondering the effect that the Magnus force and the Bernouilli principle will have on his strike? Could he be quietly deriving FD = CDrAv²/2 as he places the ball?

Unlikely, but if he did it would serve him well, for these are the forces and derivations that describe how a ball swerves when spin is put on it. The upshot if it is that if the ball is kicked hard enough the airflow over the surface will become turbulent and the drag force – which slows its flight – will remain low allowing the ball to travel very fast. Then, when it slows a little and the airflow becomes laminar, any spin on the ball will cause it to swerve according to the physical laws known as the Bernouilli principle and the Magnus force. The trick is to hit it with just the right amount of power and spin so that the turbulent (and therefore fast) flight lasts until the ball passes the defenders in the wall, with the ball slowing into laminar flow (where the ball will curve most) before the goal keeper gets to it.

Dr Ken Bray, science consultant to Southampton FC, explains: “The movement – and the spin producing it – are so complex that we have only recently had computers powerful enough to model them. Beckham, however, understands it intuitively. That is what makes him such a clever player.” If Beckham does launch a curve ball, then don’t blame the keeper if it goes in. Dr Cathy Craig, a psychologist at Queens University Belfast, has shown that humans are just not equipped to block balls struck with sidespin. She told Laboratory News: “As spinning balls are not naturally occurring phenomena, it is not surprising to discover that nature has not equipped us with a visual system that is adapted to such fast moving and unpredictable trajectories.”

Dr Craig was inspired to explore the visual system’s ability to handle swerving shots after witnessing some Brazilian magic on the pitch. “What sparked my interest in the area was seeing Roberto Carlos score a stunning goal for Brazil back in 1997 that looked like it was going wide. At the last moment though, it just curved in and completely caught the keeper unaware.”

After testing 11 players and nine goal keepers using free kicks simulated on a head-mounted virtual reality unit it was clear that those struck with spin were unpredictable - even to experience professional players.

Even though it has provided the perfect excuse for down hearted goalies the world over, some say that science is playing too large a role in modern sport and that it is replacing traditional values that make sport what it is. Science can help an athletes bend, or even break the rules and new genetic engineering technologies may offer performance enhancing drugs and therapies that will be undetectable. However, the potential legitimate advantages that it can provide are undeniable, and the scientists behind the work are finding valuable academic rewards in their chosen field.

Dr Bray explains: “It seems to me that the swerving free kick was as legitimate a topic for theoretical physics as a problem in quantum mechanics.”

By Phil Prime, assistant editor, Laboratory News