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Olympic Trials and the Olympics bring some of the most tension filled moments in sports: that endlessly quiet wait on the blocks anticipating the signal. The start of every race depends on how fast the swimmer reacts.

For analysis, we can break the start into two phases: reaction time and block time (the analysis will be almost identical for backstroke starts).

Reaction time: first movement of any kind after the signal. It is a tiny fraction of all races, but every fingernail counts in championships. Although false starts are less common in swimming than in track and field (whose shortest event is roughly half the time of the 50 free), you can’t discount the mental advantage in an evenly matched race. Further, relay disqualifications are not uncommon, even in big meets.
Block time: how long to get off the block. Block time is a measure of reaction time, start mechanics, and physical capacity. You can have the best reaction time in the field, but if your mechanics are poor, you could still be last in the water. Likewise, if you have great mechanics, the field may leave you behind if you react slowly. Block time is followed by flight time.

Our focus here will be on reaction time. (See Omega Track Start Tragedies Parts I and II for ways to improve block time) One challenge is training reaction time: how do you train reaction time efficiently and effectively, other than simply practicing starts more often? Unless you have a permanent timing system at the pool, racing is the only time you receive objective feedback on reaction time from the blocks.

Mark Russell of USA Swimming offers a dryland drill of clapping your hands after a start cue. This can easily be done in a group and does not require using an entire lane, and allows for high quantity of repetitions. However, one drawback is the lack objective feedback. Just because you practice reaction time doesn’t mean it will improve. Anecdotally, we might expect that ball sports at a young age may also cultivate reaction time (See Reactive Animal ). If all else fails, let swimmers practice reaction time on their iphones!


Another overlooked tactic is to simulate race conditions with the same start cue. Waiting on the blocks for a gun in a deathly silent arena is different than the coach yelling “Go!” over the cacophony of aqua aerobics music and noise from the learn-to-swim class in the kiddie pool. Frequent racing allows many reps in competitive settings, but not all timing systems show reaction times in the results. Ideally, for each start we’d have a number for reaction time and a number for water entry time, which can isolate how long it took to leave the blocks.

USA Swimming conducted informal research and found that men in their sample averaged 0.69 seconds reaction time compared to women with 0.73 (We can assume this data was pulled from international meets). US men had the best average reaction time of countries with more than 20 swimmers in the sample, but the women trailed Sweden and Great Britain. They offer no theories to explain these results, and the results may be statistically insignificant if exposed to more rigorous analysis, but the data is interesting nonetheless.

One factor possibly affecting reaction time is the nature of the start cue, whether a gun or a buzzer. Brown (2008) analyzed 100m and 110m track and field events at the 2004 Olympics and found that sprinters in lane 1, closest to the starting gun, had significantly decreased reaction times compared to competitors in outer lanes. As with swimming, track and field places fastest qualifiers in the middle lanes. Authors also performed experiments on trained and untrained sprinters modifying the signal intensity, from 80dB, 100dB, and 120dB. Subjects recorded significantly reduced reaction times with increasing signal intensity. Interestingly, reaction time was further reduced when authors provided the signals as a startle, suggesting the more reactive and less conscious thought involved, the shorter the reaction time.

Many theories exist on how to affect reaction time. Static stretching is often maligned in the modern sporting world, but the evidence is mixed on whether static stretching actually harms reaction time. Many athletes stretch before the race behind the blocks, often for anxiety relief. Is this practice potentially harmful, given the explosiveness of the swim start?

Behm (2004) put sixteen subjects through an acute bout of lower limb static stretching and measured several qualities, including reaction time and movement time. After the control condition (no stretching), reaction time and movement time both decreased (5.8% and 5.7%) while both qualities increased (4.0% and 1.9%) after stretching. However, Alpkaya (2007) also looked at the effect of static stretching on reaction time and found neither a positive nor negative effect. It’s important to note that these two studies employed different stretching protocols, with the Behm study using 45 seconds and the Alpkaya study using 15 seconds, which may or may not explain the conflicting results.

Another variable often linked to starts is the warm up. Warm ups have been shown helpful for overall performance, but the effect on reaction time is questionable in the evidence. Balilionis (2012) had sixteen NCAA D-I swimmers perform three types of warmups before 50yd time trials: no warmup, short warmup, and normal warmup. Although the normal warmup yielded the fastest overall performances, there was no relation between type of warmup and reaction time.

McMorris (2006) had similar findings, but with some interesting twists. After several types of warmups and a no-warmup condition, subjects performed psychomotor tasks including a reaction task, a slalom course, and soccer ball kick. Type of warmup (static, dynamic, or no-warmup) predicted overall performance, but was not related to reaction time. However, post-event heart rate was predictive of reaction time, indicating that general arousal may improve reaction independent of physical warmup strategies.

To improve reaction time, there is evidence caffeine may help. Duvniak-Zaknich (2011) studied team-sport athletes in a simulated team game and a reactive agility test. Subjects were given either caffeine or placebo. Authors noted a decrease in reactive agility time by 3.9% after caffeine ingestion and also observed improved decision-making accuracy. Additionally, authors tracked performance throughout the game to estimate whether the effect of caffeine changed during fresh versus fatigued states. Because the results were consistent throughout the game, they concluded caffeine ingestion may be helpful for reaction time under both conditions.

Feeling a bit hung over on the blocks? Sorry, a caffeinated energy drink was not able to reverse impaired reaction time caused by alcohol consumption at 0.04 and 0.08 breath alcohol concentrations. (Alford 2012)

Reaction time is a small detail, but every fraction of a second counts. Reaction time should be just that: reactive. There are several tactics to improve reaction time without getting on the blocks, but when the time comes to race, nothing can match preparing under the same start conditions as the goal meet.


  1. Brown AM, Kenwell ZR, Maraj BK, Collins DF. "Go" signal intensity influences the sprint start. Med Sci Sports Exerc. 2008 Jun;40(6):1142-8.
  2. Behm DG, Bambury A, Cahill F, Power K. Effect of acute static stretching on force, balance, reaction time, and movement time. Med Sci Sports Exerc. 2004 Aug;36(8):1397-402.
  3. Alpkaya U, Koceja D. The effects of acute static stretching on reaction time and force. J Sports Med Phys Fitness. 2007 Jun;47(2):147-50.
  4. Improving Your Reaction Time off the Blocks, Mark Russell/USA Swimming
  5. Reaction Times Across the World, Lisa Wemhoff/USA Swimming
  6. Balilionis G, Nepocatych S, Ellis CM, Richardson MT, Neggers YH, Bishop PA. Effects of Different Types of Warm-Up on Swimming Performance, Reaction Time, and Dive Distance. J Strength Cond Res. 2012 Jan 10. [Epub ahead of print]
  7. McMorris T, Swain J, Lauder M, Smith N, Kelly J. Warm-up prior to undertaking a dynamic psychomotor task: does it aid performance? J Sports Med Phys Fitness. 2006 Jun;46(2):328-34.
  8. Alford C, Hamilton-Morris J, Verster JC. The effects of energy drink in combination with alcohol on performance and subjective awareness. Psychopharmacology (Berl). 2012 Mar 29. [Epub ahead of print]

By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.

Dr. John Mullen, DPT, CSCS world-renowned physical therapist and strength coach.
  1. June 19, 2012

    Measured reaction time in swimming is almost worthless. The actual reaction time (time taken between perceiving the starting signal and onset of movement) is much less significant than the speed of the start itself. The measured ‘reaction time’, using pressure sensors, records the time taken before the feet leave the blocks. The time it takes for the signal to travel up the sensory neuron to the brain and the brain sending a signal through the motor neuron, is comparatively very short. On the other hand, the time it takes for the body to move through the start motion is much longer. So lowering a swimmer’s measured ‘reaction time’ would be more about making the start motion itself faster and more efficient. (e.g. grab start vs track start.)

  2. June 19, 2012

    Thanks for your comment Kenneth.  The difference between actual reaction time and overall start time was discussed, but maybe I wasn’t clear so I’ll repost that excerpt right here (“Reaction time: first movement of any kind after the signal.; 
    Block time: how long to get off the block….
    See Omega Track Start Tragedies Parts I and II for ways to improve block time “).
    Agreed that mathematically speaking, reaction is a relatively small portion of the entire start, but if it was entirely worthless, we’d never a false start or relay DQ.

  3. June 19, 2012

     Whoops. Sorry for skimming through the article. xP

  4. December 5, 2012

    Just curious – are there available data for reaction and block time at World/Olympic Champs similar to what is available (RT at least) for athletics. There are also a number of biomechanical projects carried out at past World Champs in athletics – does this also exist for swimming



  5. December 6, 2012

    As far as I know, there is not any data on this in swimming.

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