Abstract
Reaction time (RT) is the time needed for perception and evaluation of a stimulus and the time needed for a response. This study was designed to compare simple and choice reaction times in athletes and non-athletes at different levels of BMI. Forty-eight university students were selected as the sample of the study (24 athletes and 24 non-athletes) and were divided into three groups based on their body mass index (BMI). All participants performed simple and choice reaction time tasks alternatively. Results of independent T test indicated that athletes had shorter reaction times than non-athletes. The results of one-way ANOVA and follow-up tests showed that there was no significant difference between reaction time of athletes in three levels of BMI. Nevertheless, non-athletes with low level of BMI had shorter reaction times than the other groups (p=0.004). The findings of this study demonstrate that individuals with low BMI have a shorter reaction time.
Keywords:
Simple Reaction Time, Choice Reaction Time, Body Mass Index, Athletes and Non-athletes
Introduction
Reaction time is one of the most commonly used measures of the motor/mental performance in researches, influencing the performance of a motor ability (9). An important part of differences in speed of motor responses is attributed to reaction time. Therefore reaction time is an effective factor in success in many sports (9, 22, 25). A reaction to only a single stimulus and always that same stimulus, requiring an identical method of response is referred to as simple reaction (17). In a choice reaction, on the other hand, there are a few possibilities provided during the experiment to choose from i.e., such as the generation of a different stimulus requiring a different response (13). The results of many studies indicate that a complex stimulus (e.g., several letters in symbol recognition vs. one letter) elicits a slower reaction time (12). Then it is hypothesized that a reaction to a simple stimulus is shorter than a choice reaction time in both athletes and non-athletes.

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Many researchers seek to identify the factors that distinguish athletes and other individuals to take correct and immediate decisions. Authors such as Schmidt, Wrisberg and Magill believe that athletes with experience in a specific sport develop a greater potential in the cognitive activities (10, 21). Nakamoto(2008) and Mori (1989) found that university students who played basketball and baseball had faster reaction times than sedentary students(14, 11). At least in baseball players, the more they were experienced, the faster they reacted to baseball-specific stimuli. Fontani et al. (2006) showed that in karate, more experienced practitioners had shorter reaction times, but in volleyball, the inexperienced players had shorter reaction times (and made more errors too)(4). Mero (1989) reported no significant difference in simple reaction time between novice and expert tennis players(11). Not only with baseball or tennis players, but also with clay shooters (1), basic visual functions, including simple reaction time, were not a limiting factor to performance in sports.
These non-conclusive indications about the relation between experience in sport and motor time reaction direct us to compare the results of test of reaction time in athletes and non-athletes in this study. On the other hand, there are some contradictions in the literature in terms of the relationship between body physique and RT in healthy participants (22). Henneberg et al. (1998) and Stamm et al. (2005) emphasized the importance of examining the relationship between body physique and functional variables such as RT(7, 24). Although several studies reported significant correlation between physique and RT (e.g. Janoff et al., 1950; Smith and Boyarsky, 1943), there is still a lack of published data relating reaction time to body mass index (7, 23). Jette et al. (1988), however, working with healthy young adults found no difference in RT between different groups classified in relation to percentage of body fat(8). Therefore, this study aimed to compare athlete and non-athletes in three groups of BMI in the way they respond to simple and complex stimuli.
Method
Participants
Forty eight participants (24 athletes and 24 non-athletes) took part in the study. Athletes were selected from male university students with at least 2 years of experience in their specific sport and non-athlete participants were university students without professional sport experience. The WHO Technical Report Series, 854 (1995) defines the range of BMI from 25 to 30 as high or overweight, from 20 to 25 as mid-weight, and below 20 as low or underweight(27). Sampling was done based on participants’ BMI; therefore, based on the three BMI levels in both athlete and non-athlete groups, we had six sub-groups. Hence, we assigned 8 participants to each sub-group.
Instrument
The instrument used in this study to calculate BMI was In Body 3.0 body composition analyzer (by Bio Space Company). This instrument also can provide information about the body fat, fluids, muscles, etc. Reaction time was measured by reaction time apparatus (Model Y1000 – by Takei Company). It is consisted of a screen and a keyboard with three buttons. The screen was in a distance about 80 centimeters from the participants.
Procedure
The participants were seated on a chair in front of a screen displaying three visual signals: Yellow, Red and Blue under a resting condition. The subjects responded to visual stimuli, as quickly and accurately as possible, by pressing related buttons with the thumb. The simple RT task consisted of responding to a visual red-colored stimulus. Also, three response signals were randomly presented on the display for measuring choice reaction time. Each signal corresponded to a specific response. The first 10 trials were performed by the participants in order to become familiar with the test conditions and the results of these trials were not included in data analysis (3, 9). Then, 40 trials performed into two blocks of 20 trials(22). A five-minute rest time was given to the participants between the two blocks. Each trial started at random intervals (2-4 seconds) as recommended by the previous studies (3, 9).
Data analysis
The statistical analysis was performed using SPSS 15. Independent t-test was used to compare RT in athletes and non-athletes. The data were analyzed for significant differences using an analysis of variance (ANOVA). Tukey follow-up analyses were conducted on all significant interactions at P<0.05 levels.
Results
In table 1 the scores of participants (athletes and non-athletes) in simple and choice RT has been presented. The results of t-test indicates significant differences in simple reaction times between the two groups (P=0/008), but no significant difference was found in choice RT (P=0/250).
Table 1 – scores of participants in simple and choice reaction times
Participants
Mean
d.f
F
Sig
Simple RT
athlete
0/213
58
0/859
0/001
non-athlete
0/232
Choice RT
athlete
0/453
58
0/355
0/155
non-athlete
0/480
Simple reaction time:
Table 2 depicts the results of a 2-3 ANOVA on reaction time. As indicated in this table, there was significant difference between the 6 sub-groups (P=0/004). Tukey analyses also were performed to reveal the differences between sub-groups (see table 3). Results of the follow-up analyses can be listed as following:
Tukey follow-up test did not show any significant difference in RT between three BMI levels in athletes; however, there were negligible differences.
By analyzing the RT of athlete participants in three different levels of BMI, significant difference between high and low BMI groups was found (P=0/024). Also high and mid BMI groups of non-athletes showed significant difference (P=0/008). But the difference between mid and low BMI groups was partial (P=0/456).
The Results of comparison between the two groups of participants (athletes and non-athletes) indicated that athletes with mid and high BMI were statistically different (P=0/462).
Table 2 -one way analysis of variance (ANOVA) results for simple RT
variable
sum of squares
Mean of squares
d.f
F
Sig
within group
0/009
0/002
5
3/983
0/004
between groups
0/025
0/000
54
overall
0/035
59
Table 3 – follow up test results for simple RT
participants
comparison groups
mean differences
sig.
level of expertise
level of BMI
athlete
low
mid BMI athlete
high BMI athlete
low BMI non-athlete
-0/008
-0/006
-0/008
0/940
0/989
0/976
Mid
low BMI athlete
high BMI athlete
mid BMI non-athlete
0/008
0/001
-0/029*
0/940
1/000
0/002
High
low BMI athlete
mid BMI athlete
high BMI non-athlete
0/006
-0/001
-0/022*
0/989
1/000
0/040
non-athlete
low
mid BMI non-athlete
high BMI non-athlete
low BMI athlete
0/008
-0/029*
-0/030*
0/462
0/008
0/024
Mid
low BMI non-athlete
high BMI non-athlete
mid BMI athlete
0/029*
0/029*
-0/008
0/002
0/008
0/456
High
low BMI non-athlete
mid BMI non-athlete
high BMI athlete
0/022*
0/030*
-0/008
0/040
0/024
0/456
Choice reaction time:
The choice reaction time in athletes and non-athletes was measured in the same was as simple reaction time. As indicated in table 4, there was significant difference between groups (P=0/049), but follow-up analyses revealed that only the difference between high BMI sub-groups was statistically significant [(P=0/021), see table 5].
Table 4 -one way ANOVA results for choice RT
variable
sum of squares
Mean of squares
d.f
F
Sig
within subject
0/053
0/011
5
2/40
0/049
between subject
0/238
0/004
54
overall
0/291
59
Table 5 – follow up test results for choice RT
participants
comparison group
mean differences
sig
level of expertise
level of BMI
athlete
low
mid BMI athlete
high BMI athlete
low BMI non-athlete
0/011
0/055
-0/0001
0/999
0/561
1/000
Mid
low BMI athlete
high BMI athlete
mid BMI non-athlete
-0/011
0/044
0/016
0/999
0/609
0/990
High
low BMI athlete
mid BMI athlete
high BMI non-athlete
-0/055
-0/044
-0/109*
0/561
0/609
0/021
non-athlete
low
mid BMI non-athlete
high BMI non-athlete
low BMI athlete
0/0002
0/028
0/053
1/000
0/957
0/592
Mid
low BMI non-athlete
high BMI non-athlete
mid BMI athlete
-0/016
-0/028
-0/081
0/990
0/957
0/154
High
low BMI non-athlete
mid BMI non-athlete
high BMI athlete
0/109*
0/053
0/081
0/021
0/592
0/154
On the other hand, the results of Body Composition analysis revealed that athletes at all BMI levels had higher levels of muscular tissue and lower levels of fat tissue, but participants in the non-athlete group with low BMI had less fat tissue rather than the two other BMI levels in their group.
Discussion and Conclusion
This study was an attempt to explore the differences between athletes and non-athletes in reaction times. In previous studies, subjects were mostly athletes, but in the present study subjects consisted of athletes and non-athletes. The findings of indicated that athletes had faster reaction time than non-athletes and the difference between the two groups was statistically significant. These findings confirm the effect of physical activity and doing sports on improving reaction time which is supported by the results of previous studies in this area (2, 16). Plesnicar (2004) in a study on two groups of participants, showed that experimental group after 8 weeks of physical practice, had faster simple and choice RT than the other group which had had no physical practice (16). Besides, Ramos and Santos (2005) found that there was a high negative correlation between RT and training experience (2). Magill (2000) believes that more experienced athletes develop an ability in cognitive activities and information processing. This development of abilities is because athletes adapt themselves to unstable environmental conditions and different stimuli, which can cause faster RT and accurate problem solving abilities. The first part of RT (pre-motor period) is related to cognitive functions which are affected by experience in physical activity and sport. As Schmidt and his colleagues (1990) noted, participation in sports-related activities enhances the cognition and consequently leads to an increase in the speed of information processing which can shorten the RT (19).
Moreover, it has been declared by researchers that RT is consisted of pre-motor and motor periods and the difference between athletes and non-athletes is primarily related to motor period. Davranche, morales and Maciel (2009) in an electromyographic study on athletes and non-athletes found no difference in pre-motor time between athletes and non-athletes, but motor time was significantly shorter in athletes than non-athletes (3). As skurvydas and his colleagues (2008) discussed, whereas athletes benefit from a higher degree of fitness and bulk of muscles, they are faster in overcoming the initial inertia of the body and starting the movement. Physical activity also enhances the transmission of neural impulses (22). Thus, highly trained athletes have faster neural transmission in their peripheral system which results in shorter motor time and shotter overall reaction time. The results of the present study along with previous studies confirmed the existence of a great difference in motor time between athletes and non-athletes.
As noted earlier, the difference in reaction time between athletes and non-athletes was statistically significant only in simple RT. In choice RT, however, athletes had a faster reaction time but the difference was not significant. Barcelos and colleagues (2009), comparing elite and novice volleyball players, found that experienced athletes were faster in recognition RT, although there was no significant difference in simple RT (2). Miller and Low (2001) determined that the time for motor preparation and motor response was the same in all three types of reaction time test, implying that the differences in reaction time are due to processing time. Therefore, regarding the result of the present study, we can conclude that even if body physique, because of its effect on motor preparation, has a role in delaying reaction time, it does not cause any differences in the way individuals respond to simple and choice stimuli.
This study demonstrated that athletes in three BMI levels had no significant difference in simple reaction time. An important factor in measuring the reaction time is acceleration, which means overcoming the primary inertia of the body. According to Newton’s second law, the more the mass is, the less the acceleration () will be. In other words, individuals with lower weights overcome the body’s inertia faster and have more acceleration in their movements. Naturally, they have faster reaction times (5, 8, 18). As the results of body composition test showed, athletes in all BMI levels had more musculature. Therefore, the muscle bulk of athletes in high BMI level group compensated for their excessive mass because the muscles generate force. There was no difference in the reaction time of the athlete participants with all BMI levels and their reaction time was shorter than non-athlete participants.
Chen and Hallett (1999) indicated that the reaction time is affected by participants’ level of awareness and individuals with overweight and high level of BMI have lower levels of awareness (22). This is consistent with the results of our study showing that there was a positive relation between level of BMI and RT. The findings show that participants with high BMI levels in both groups had longer reaction times. It means that overweight individuals have lower awareness level and, as a result, they have shorter reaction times.
To summarize, the results showed that anthropometric characteristics have important and effective role in simple reaction time. These findings suggest that anthropometric factors plays an important role in the specialized movement phase in the specific sports individuals play, especially in sports with high importance of reaction time.