Wednesday, 16 October 2013

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