Reaction Time
Reaction time refers to how quickly one can respond to a given stimulus. Success in many sports depends on an athlete’s ability to react and make split second decisions. There are plenty of examples that illustrate the importance of an athlete's ability to react.
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a swimmer needs to be quick off the starting blocks.
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how a sprinter reacts to the start gun could make the difference between winning or losing a race.
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a cricket batsman needs to react quickly to a ball that can be bowled over 150 kph.
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a goalkeeper has to make a quick decision on whether to come out to catch a cross or stay on the goal line.
Sleep deprivation studies on reaction time
Taheri and Arabameri (2012) conducted a study where participants completed a reaction test which involved a computer that was connected to two joysticks (one for each hand). Two empty squares were shown horizontally on a monitor.
When one of the squares filled with red, the participant had to tilt the appropriate joystick as quick as possible to signify whether it was the left or right square that was filled red. Participants were tested after at least three nights of regular sleep, and then after sleep deprivation (they were kept up overnight and completed the test at 9am the next morning).
When participants were sleep deprived, their reaction time slowed by 15%.
Suppiah, Low, and Chia (2013) looked at the sleeping patterns of 29 male high school athletes. They discovered that during weekdays, the students incurred a sleep debt, i.e., they slept on average for just 5.5 hours per night. However, over the weekend, students extended their hours of sleep, probably due to the fact they did not have to get up early to attend class.
On reaction time tests, the athletes performed faster on Monday compared to the end of the week (Thursday and Friday). The hypothesis was, the reason athletes performed worse at the end of the week was because of the sleep debt they incurred, in contrast to Monday when they were better rested from the weekend.
Vedaa, Saxvig, Wilhelmsen-Langeland, Bjorvatn, and Pallesen (2012) conducted a similar study with Norwegian junior school students. The students started their day at 9.30am on Monday (1 hour later than normal). Their start time was 8.30am for the remainder of the school week. The researchers wanted to learn whether the opportunity of extra sleep on Sunday night would affect performance in a reaction time test.
Sleep duration was checked and the students achieved at least an additional hour of sleep on Sunday night in comparison to the control group (which was a group of different junior high school students who started at 8.30am, Monday to Friday). The results of the reaction test showed that the students from the school who received the additional sleep on Sunday night, performed better on Monday compared to Friday, relative to the control group.
Van Dongen, Maislin, Mullington, and Dinges (2003) showed that cumulative sleep loss (sleep debt across multiple days) also has a negative effect on a reaction time task. Participants were randomly assigned to one of the following groups where their sleep was restricted to either:
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4 hours per night for 14 days
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6 hours per night for 14 days
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8 hours per night for 14 days
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3 nights without any sleep
The results showed reaction time erroded for the 4 and 6 hour group (worst for the 4 hour group) relative to the 8 hour group, and performance fell to a level that was equivalent to those that were totally sleep deprived for 1 to 2 days! So sustained sleep restriction even over a short period of time seems to impair reaction times.
Would you compete intoxicated?
Hopefully the answer to that question was no. It's widely accepted that alcohol consumption impairs our concentration, reaction, coordination, and decision making. If you are of drinking age, it's quite likely that you have some personal experience in these matters.
A study by Williamson and Feyer (2000) showed that a lack of sleep produces a similar decline in reaction time to that of being intoxicated. The study involved 30 participants (aged 30-49), who completed reaction time and hand eye coordination tests, when sleep deprived and again while intoxicated.
For the alcohol test condition, participants woke up at 6am, and were given doses of alcohol at 4 hourly intervals starting from 8am, with the intention of increasing their blood alcohol concentration (BAC) level to .025%, .05%, .075%, and .1% after each dose. The participants completed a series of tests at the start, and then 30 minutes after consuming each dose of alcohol. For the sleep deprived condition, participants woke up at 6am, and completed 15 series of tests at varying times over the next 28 hours, without any sleep during that time.
BAC is an indicator of one’s intoxication, and refers to the percent of blood that is concentrated with alcohol. E.g. a BAC of 0.05% means you have 0.05g of alcohol in every 100ml blood. The legal driving limit for BAC in the UK is 0.08% (except Scotland which is 0.05%).
The researchers discovered performance decrements in both conditions. After 17-19 hours without sleep, the performance on most tests when sober (but sleep deprived) were similar to when they had a BAC level of 0.05% - the alcohol driving limit in Scotland!
The moral of the story
If reaction time is important in your sport, then managing your sleep could be of huge benefit.
Learn more.....
MODULE SLEEP
The impact on performance
References
Suppiah, H.T., Low, C.Y., & Chia, M. (2016). Effects of sport-specific training intensity on sleep patterns and psychomotor performance in adolescent athletes. Pediatric Exercise Science, 28 (4), 588-595.
Taheri, M., & Arabameri, E. (2012). The effect of sleep deprivation on choice reaction time and anaerobic power of college student athletes. Asian journal of sports medicine, 3 (1), 15–20.
Vedaa, O., Saxvig, I.W., Wilhelmsen-Langeland, A., Bjorvatn, B., & Pallesen, S. (2012). School start time, sleepiness and functioning in Norwegian adolescents. Scandinavian Jounral of Educational Research, 56 (1), 55-67.
Van Dongen, Hans P.A., Maislin, G., Mullington, & J. M., Dinges, D.F. (2003). The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology from Chronic Sleep Restriction and Total Sleep Deprivation. Sleep, 26 (2), 117–126. Web.
Williamson, A.M., & Feyer, A.M. (2000). Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occupational and Environmental Medicine, 57 (10), 649-655.