Relationship Between Exercise and Reaction Time: Research

EXERCISE AND REACTION TIME

RESEARCH QUESTION:

How, and to what extent, do varying intensities of aerobic exercise affect the visual and auditory reaction times of males between ages 15-20?

INTRODUCTION:

The field of reaction time has been one with much interest and study over the past few years, especially given its pertinence and applicability in things ranging from athletics and sport science to motor skills and road safety. Looking at the fluid, almost unnaturally effortless movements of world-class sportsmen leads one to question whether or not the rapid decision making needed for optimal athletic performance is in any way affected by their overall fitness.`

But at this juncture, let us try to usher in some clarity. Reaction time is defined to be the time lapse between the presentation of a sensory stimulus and the initiation of the subsequent muscular motor response. It is an external indicator of the ability of the central nervous system to receive process and respond to incoming stimuli. These stimuli travel to the brain through electrical impulses and reach the brain as sensory information. The brain then makes a decision, and neural transmissions start to generate a motor response. The measurement of one’s reaction time is a common method used to evaluate one’s psychomotor performance and fitness.

A typical reflex arc in vertebrates is shown below:

Stimulus  Sensory neuron  Spinal cord or Brain  Motor neuron  Response

It has been proven, Shelton and Kumar (2010) that auditory reaction times are generally faster than visual reaction times. Pain and Hibbs (2007) showed that it takes only 8-10 milliseconds for an auditory stimulus to reach the brain whereas it takes 20-40 milliseconds for visual stimulus. The average visual reaction time is about 250 milliseconds whereas the average auditory reaction time is roughly 170 milliseconds.

Now, it’s been further well documented that there are numerous factors that affect reaction time. Excluding factors like stimulus intensity or type of stimulus, factors that can have a significant affect include:

• Arousal– The state of arousal of a person greatly affects his reaction time. It has oft been suggested that the slowest responses are when the subject is too tense or too relaxed and that the fastest reaction times were found at a state of moderate arousal, resulting in a bell-shaped curve.
• Importance of stimulus– A life threatening situation, for example, is more likely to elicit a fastest response than a more mundane situation.
• Age– A study conducted by Der and Deary (2006) shows that Reaction times usually deteriorate as a person grows older. This can be attributed to the fact that older people have a much slower nervous system and so they generally take more time to make decisions.
• Fatigue– Tiredness slows down reaction time drastically, especially mental fatigue. Mental fatigue can be caused by sleep deprivation, which is why you should not drive when you are tired or sleepy.
• Practice– Practiced responses tend to have faster reaction times, for example people playing a certain sport may have fast reaction time for that particular sport. Discontinuing the practice may cause reaction times to worsen.

There are 3 main types of reaction time, however only simple and choice reaction times were measured in this study.

• Simple reaction time: This involves the individual being subject only 1 stimulus, to which there is only 1 possible response. Simple reactions tend to be the fastest of the 3 because there is no time spent by the brain making decisions.
• Choice reaction time: In such an environment there are multiple stimuli, with each having a designated response. This reaction time is generally longer, because the brain has to associate a certain stimulus with its corresponding response.
• Recognition reaction time: This type of reaction time test involves multiple stimuli, to which there is only 1 correct response. This sort of reaction is much slower than simple reaction time because the brain must distinguish between the distracting, misguiding set of stimuli and the correct response.

The reaction time pioneer Donders (1868) found that simple reactions are the fastest, recognition reactions are slower and choice reactions tend to be the slowest of them all.

All this is abridged in the table below, with an example of a basic, preliminary experiment that could be used to consider each type of reaction.

Now, exercise has been proven to enhance physiological functioning as well as various other aspects of mental functioning such as self-esteem, mood, cognitive abilities and general psychological well-being. Regular exercisers also sustain much lower risk of developing mental disorders in comparison to their more sedentary counterparts.

Cardiovascular, or aerobic, exercise refers to activity performed at a moderate intensity undertaken for a medium to long duration. Cardiovascular exercise involves exercising at an intensity that is roughly around 50-80% of the individual’s maximum heart rate.

This study was, ergo, carried out to determine the effect, if any, of various intensities of exercise on visual and auditory reaction times.

PROCEDURE:

1. 5 people, who did not exercise regularly, or at all, were chosen to be part of the control group and 5 people who were regular exercisers formed the experimental group.
2. Each of their resting heart rates were recorded using the in-built heart rate sensor in the treadmill.
3. All visual reaction time experiments were conducted in a well-lit room and all auditory reaction time experiments were performed in a quiet, unperturbed room.

VISUAL REACTION TIME: SIMPLE

4. The subjects were made to sit down on a chair and were instructed to catch a ruler that was going to be dropped between their fingers, as fast as possible.
5. Any readings below 5cm were considered as anticipated responses and were discarded.
6. The ‘0’ cm mark of the ruler was placed just above the gap between the thumb and index finger and, without warning, the ruler was dropped. The subjects caught the ruler as fast as they could. They were each allowed 3 test trials.
7. This was repeated 5 times and a mean was calculated.
8. Each subject’s individual maximum heart rate (MHR) was then calculated by subtracting their age by 220.
9. They were then made to exercise on a treadmill until 50% of their MHR was achieved.
10. Steps 4 and 5 were repeated.
11. Step 7 and 8 were then repeated at 60% and 70% of the MHR of each subject.

VISUAL REACTION TIME: CHOICE

12. The subjects were instructed to open both their hands similar to in the simple reaction time test and plant their elbows firmly to their sides.
13. This time, 2 rulers were used, one over each hand.
14. Readings below 10cm were considered as anticipated responses and were discarded.
15. Enough test trials were conducted, until the subjects were familiar and comfortable enough to not completely miss the ruler.
16. The subjects were instructed to catch only the one that is dropped, without squeezing the other hand.

NOTE: It is vital that only one hand is closed and not both, since squeezing both hands would defeat the purpose of this choice experiment.

17. Without any warning whatsoever, one of the rulers was dropped and caught by the subjects.
18. This was repeated 5 times and a mean was calculated.
19. Using the calculated MHR, the subjects were made to exercise at 50% of their MHR and steps 10-15 were repeated.
20. This entire process was performed again with 60% and 70% of the subjects’ MHR

AUDITORY REACTION TIME: SIMPLE

21. The subjects were made to wear a blindfold to cut off all visual stimulus so that they can focus solely on the sound stimulus.
22. The set up was identical to the simple visual reaction except that the stimulus in this test was the word “Catch”.
23. Readings below 5cm were considered as anticipated responses and were not counted.
24. With the blindfold on, the ruler was placed just above the thumb and index finger and the word “Catch” was spoken. Simultaneously, the ruler was dropped and the subjects closed their hands as soon as they heard the word.
25. After 5 trials each, a mean was calculated.
26. This process was repeated with 50%, 60% and 70% of their MHRs

AUDITORY REACTION TIME: CHOICE

27. Wearing a blindfold, the subjects were made to sit with their arms placed firmly at their sides with both their hands open in the pre-determined position.
28. The two rulers were placed, one above each hand, and the subjects were instructed to close only one hand in response to the stimulus.
29. The words “left” and “right” were the two stimuli corresponding to which hand they should close.
30. Readings below 10cm were considered as anticipated responses and were not counted.
31. Without warning, either “left” or “right” was called out and the corresponding ruler, dropped. The subjects responded by closing the hand that was called out.
32. This was repeated 5 times and a mean was calculated.
33. The full process was then repeated at 50%, 60% and 70% of the subjects’ MHR.

DATA COLLECTION:

DATA PROCESSING:

The reaction time, in seconds, was calculated using the formula:

t =

where t is time, in seconds, d is the point on the ruler that was caught, in cm, and g is the gravitational force that is 980, measured in cm/s²

SAMPLE CALCULATION:

If the subject caught the ruler at the 20cm mark, inputting that value in place of d in the formula we get:

t =

= 0.2s

Since reaction time is commonly measured in milliseconds and not seconds, the values were simply multiplied by 1000:

0.2 x 1000

= 200ms