The A - Z of Sports Vision - Umpires

I was recently one of the tutors on a course for aspiring cricket umpires. There was a discussion about where the bowler’s end umpire should stand so that he can see the bowler’s feet land (making sure it’s not a No Ball) as well as the flight of the ball.

They were given the standard advice that they should keep their head still and flick their eyes down to see the landing of the feet, and then flick them up to watch the ball and where it pitches so they can adjudicate for LBW and other decisions. It was assumed that I, as an optometrist, would back this up. It was a little awkward when I had to say that conventional wisdom was actually wrong. It is true that batsmen, for instance, should keep their head still at the moment of contact. You’ll see many batsmen lift their head when they go for a big shot and either miss the ball or sky it into the air. I used to think that this was due to over-anticipation of where the ball was going to go, or just some kind of “red mist”. But I’ve now come round to the idea that it’s our old friend balance. If you’re moving forward and you’re not well balanced, you’re likely to fall flat on your face. In order to prevent this, your brain brings your head up so that your centre of gravity moves backwards. You don’t execute the task very well but at least you don’t fall over. If your rugby scrum half is firing the ball over the fly half’s head, it’s for the same reason. Anyway, I digress. None of this means that keeping your head still is the best way to track a moving object. Hold a finger in front of you and move it slowly from side to side. Follow your finger with your eyes only, keeping your head still. Gradually increase the speed of your finger. You’ll very soon find that you’re losing focus. Now try again, this time moving your head and eyes together. You’ll probably start to get dizzy before you lose focus on your finger. It’s one of those lovely examples when conventional wisdom – everything you thought was right – turns out to be wrong. David Donner

The A - Z of Sports Vision - Tau

Hofsten (1983) videotaped infants between 34 and 36 weeks as they reached out towards a brightly-coloured object travelling in a circle. In 144 reaches, they only missed 17 times, and the mean timing error was just 4.4ms when the object travelled at 45cm/second. McLeod, McLaughlin & Nimmo-Smith (1986) asked non-games players to hit vertically-dropping squash balls towards a target with a bat. They were extraordinarily consistent, with standard deviations of just 10ms in 90% of trials, and only 5ms in 50% of trials. So “ordinary people” can demonstrate fine timing even without any particular practice. How do we manage these extraordinary calculations? The answer is that we don’t calculate them. Suppose you are a fielding on the boundary in cricket and the ball has been hit in the air towards you. To calculate the balls arrival (Time-to-Contact or Tc), you’d have to estimate the distance the ball has to travel and its speed, and then divide one by the other. This doesn’t seem a likely method for adults, let alone infants. Lee (1976) proposed that the time to contact could be assessed by using changes to the size of the image that an object creates on retina as it approaches. For our fielder in the deep, the ball approaches him at a fairly constant speed. But when it’s far away, the size of image it forms on the retina doesn’t change much. As it gets nearer, however, the image size gets larger at an increasing rate. The ratio between the image size and the rate of expansion of that image size is known as tau (it’s actually the ratio of visual angle of rate of change of visual angle, but you get the idea). Tau can be used to predict the time at which an object travelling at a constant speed will reach us, and therefore the time at which we need to instigate a movement to intercept it. In a brilliant experiment, Savelsbergh et al (1991) got subjects to catch a ball one-handed. But the ball actually consisted of a small ball 5.5cm in diameter surrounded by an inflatable balloon 7.5cm in diameter. As the balloon approached the catcher it was mechanically deflated without he catcher’s knowledge, so by the time it reached the catcher’s hand it was the same diameter as the small ball. The ball was travelling at a constant velocity, so if the catchers were using that velocity to judge when the ball would arrive, they should still catch it. But because the ball was deflating, the ball’s image on the retina did not expand at the expected rate, so the catchers were late in their attempts to intercept the ball. This proved that the catchers were using tau when catching. Of course for the fielder on the boundary the ball isn’t coming in a straight line, it’s in a parabola, and the fielder may well have to run laterally to get to it. There are other visual strategies that can be used for successful catching, but that’s for another blog. David Donner

Following In The Footsteps of Cricketing Giants

I once met a cricket master at a local public school who, some years previously, had taken a team of boys to India. He told me that one of his opening batsmen had asked his opposite number, by way of conversation, what their highest opening partnership had been. “664” was the reply. This partnership, between Sachin Tendulkar and Vinod Kambli, was made in Mumbai’s inter-school Harris Shield, and Tendulkar made 326, not out.

In the past three seasons, three cricketers have broken Tendulkar’s record in the same competition. Remarkably, they all played for the same school team – Rizvi Springfield in Mumbai. Sarfaraz Khan made 439 at the age of just 12. Earlier this year, and still only 15, he smashed a century for India Under-19 against South Africa in just 66 balls. Armaan Jaffer scored 473 at the age of 14, having previously scored 498 in another tournament two years previously. Now, Prithvi Shaw has eclipsed them by making 546 shortly after his 15th birthday. Pritvi’s story is quite remarkable. When he was just 4 years old his mother died, by which time he had already enrolled in the local cricket academy. At the age of 8 he started commuting to Rizvi Springfield School in West Mumbai with his father. Speaking on the BBC’s “Outlook” programme, this is how he described his day: “It was quite hard to travel. So we wake up at 4 o’clock, get the train at 6 o’clock….my school starts at 8.00 so it was a quite busy schedule. After my school from 8.30 to 2.30 I was having MIG practice (his cricket club in Mumbai). The practice was from 3 o’clock to 6.30. And then go to tuition at 8 o’clock, and then coming back at 11/11.30, and then eating then sleeping”. And it’s not just in Mumbai. Krishna Narayan from Kerala has become a YouTube sensation after his father posted videos of him batting form the age of 4. He’s now 9 years old. These kids generally have fathers who are somewhere on the spectrum from very supportive to extremely pushy to living their dreams through their kids. And therein lays the danger. In fact there are two dangers. Firstly, the father’s anxiety for the son to succeed transmits itself to the child who therefore loses the enjoyment of just playing. And the second danger is that the child believes that he is naturally supremely talented and doesn’t develop the mental strength to deal with setbacks. For an excellent article on this, see: http://thetalentcode.com/2010/09/08/how-to-raise-a-prodigy-and-how-not-to/ At least they are unlikely to suffer the date of probably the greatest batting prodigy of all. In 1899, 13-year old AEJ Collins scored 628 not out playing for Clarke’s House, Clifton College, Bristol. This remains the highest score ever made in a competitive cricket match. Although he batted over four afternoons, he actually spent less than seven hours at the crease. Born in India, he was already an orphan by the time he began at Clifton, where he held a scholarship. A sporting all-rounder, he played half-back for the rugby XI, and won a bronze medal for boxing at a public school competition in 1901. He never played first class cricket, but joined the Army. In 1914, at the age of 29, he was killed in the First Battle of Ypres. David Donner

The A - Z of Sports Vision - Sleep

The importance of a good night’s sleep is often underestimated in sport. Mah et al (2011) studied the effect of giving college basketball players an extended sleep (between about 80 and 110 extra minutes). They found that the players were able to sprint faster, and were 9% more accurate in their free throws. By contrast, Winter (2013) found that the higher the level sleepiness of a Major League Basketball player, the less likely he would still be in the league three seasons later. And all this has more to do with the eyes than you might think. Many with be familiar with the two light receptor cells in the eye – the rods and cones. But here’s another group of cells known as photoreceptive retinal ganglion (prg) cells. The existence of these cells had first been proposed in 1923 by a Harvard graduate called Clyde Keeler, who noticed that the pupils of mice reacted to light even when they had no rods and cones. The idea lay dormant until the 1990s, when Oxford Professor Russell Foster was studying circadian rhythms, the daily cycles of our bodies, which appeared to be related to light levels. It was known, for instance, that if people live in the dark for days on end, their circadian rhythms drift, so they might end up sleeping in the day rather than at night. In 1999 Foster found that mice who had eyes, but no rods and cones, kept the same circadian rhythms as sighted mice. Then, in 2002, Berson et al found that these prg cells contained a photosensitive pigment called melanopsin, showing that this was the mechanism that’s used to set our daily cycles, including our sleep cycles. This explains why there are some completely blind people who are able to tell whether or not a light is on in the room, even though they don’t know how they do it. When melanopsin is stimulated, we become more alert and wakeful. And it’s most stimulated by blue light. So if you want a really good night’s sleep, you need a dark room, but you can have some red light as this doesn’t stimulate melanopsin. Leaving your curtains slightly open may give enough blue light to get you going in the morning, so you can start preparing for your sporting endeavours of the day. David Donner

The A - Z of Sports Vision - Reaction Times

Research into reaction times goes back more than a hundred years. In 1911 Ladd & Woodworth produced average reaction times for visual, auditory and kinaesthetic (touch) stimuli as 189.5ms, 146ms and 150ms respectively. Since then, other researchers have found similar figures, although improved technology has shown reaction times for kinaesthetic stimuli to be the quickest, at between 120 and 140ms (Vickers 2007). You can actually break reaction times down into different phases. Firstly, the stimulus has to be recognised and an appropriate response prepared. Then there’s a phase where the muscles begin to contract (as measured by electromyography – EMG) but there’s no movement. Finally there’s a phase where the movement response can be observed. Although the average auditory response time is 140-160ms, the threshold for Olympic sprints is lower because reaction time can be decreased with training (Carlton 1981). When Linford Christie was disqualified (see J is for jumping the gun) the threshold was 100ms, but it’s since been raised to 120ms. A group led by Joan Vickers looked at the reaction times of baseball player Mark McGwire. In his career McGwire averaged a home run every 10.61 at bats, the best at bats home run ratio in baseball history (Babe Ruth is second). They looked at videos of his record-breaking 1997-98 season, measuring his reaction time (the time between the release of the ball from the pitcher and the movement of the bat towards the ball) and his movement time (the time between the first forward bat movement and contact with the ball). They found that McGwire waited longer before moving his bat than other great players, and swung his bat faster than any other player in history. This fits in with research by Bahill & LaRitz (1984) who found that college players tracked the ball until it was around 2.75 metres from the plate while Major League players kept up with the ball until it was almost 1.5 metres form the plate. McGwire’s performances don’t appear to have been because of exceptional vision – he actually had poor acuity in one eye and wore contact lenses when playing. This suggests that his ability was more due to anticipation as a result of practice than an innate ability. For instance, batters do anticipate at least partly on the basis of previous balls and strikes against them. Laboratory-based research has found that batters’ decision-making processes were 60ms faster when they had this “count information” compared with when it wasn’t available (Farrow & Kemp, 2003). McGwire may have had one advantage, however: in 2010 he publicly admitted to using performance-enhancing drugs throughout his career. David Donner

The A - Z of Sports Vision - Quantum Biology

“Q” should really be for the Quiet Eye, but as I've already talked about that, it’s an opportunity to talk about a sport that’s rarely mentioned in terms of sports vision – pigeon racing. The term quantum biology was first coined by Edwin Schrödinger (of Schrödinger’s cat fame) in 1944. It’s always seemed miraculous that birds are able to navigate so accurately over such long distances. It’s been assumed that they do this by using the earth’s magnetic field, but it’s only recently that our understanding of quantum physics has enabled us to speculate on how they actually do it. As soon as one enters the world of quantum physics, things start to get seriously weird pretty quickly. For instance, in quantum superposition, particles can have different states such as a particle or a wave, until you observe them. To take the idea to an absurd level, Schrödinger suggested that a cat in a sealed box could be both alive and dead until the box was opened. There is also the phenomenon of “entanglement” in which unconnected particles influence each other, so that measuring one affects the measurements of the other. It’s this process of entanglement that is thought to take place within the bird’s retina that enables it to navigate. The idea is that a photon entering the bird’s eye releases a pair of molecules, each with an unpaired electron. Each of these electrons has an angular velocity, or spin, that can be altered by a magnetic field. Under quantum entanglement, the spin of one electron will affect the spin of the other, no matter how far apart they are. The birds might even have an image of the magnetic field that overlaps the visual image. So far, the only suggested use of quantum biology in humans is that it may explain how we are able to distinguish different smells. But it’s early days; who knows what we may find out in the future? David Donner

The A - Z of Sports Vision - Paralysis by Analysis

Take something you do every day without thinking about it – brushing your teeth, for instance, Next time you brush your teeth try and think about the precise movements that you are making with your hand. If you manage to keep this up for a while, you’ll find that brushing your teeth is no longer the simple process that it was on the previous occasion. If you start thinking about the mechanics of a routine process that we normally do sub-consciously, the result is that our performance deteriorates: “paralysis by analysis”. This is particularly common in sport: when something goes wrong, it’s very tempting to start analysing the mechanics of what happened, with the result that a blip becomes a catastrophe. Jackson & Beilock (2008) asked skilled soccer players to dribble the ball through a series of pylons while paying attention to the side of their foot that most recently contacted the ball. Their performance was worse in terms of being slower and having more errors compared with when they were given no instructions. Similar results have been found in baseball where skilled university-level players were asked to perform a hitting task. They heard a randomly presented noise and were told to indicate whether their bat was moving up or down at the instant they heard the noise. Biomechanical swing analysis revealed that the resultant deterioration in performance was at least in part due to a disruption in the sequencing and timing of the components of their swing. The more complex the skill, the greater is likely to be the loss of performance when the player concentrates on the step-by-step components of that skill (Masters et al 1993). It’s also more likely to occur in a high pressure situation, such as hitting a golf putt to win a golf championship (Masters et al, 1993). And it’s golf, and in particular Tiger Woods, that has given us an example of how paralysis by analysis can be overcome. Tiger’s father Earl taught him to putt when he was just a toddler. He told him to rotate his head and really look at the hole, then come back to the ball. He repeated this two or three times until he built up a picture in his head. All he had to do now was to “putt to the picture”. In other words you want to tell your subconscious brain, in as much detail as possible, exactly what you want it to do. But don’t tell it how to do it. David Donner