Reaction Times to Light Stimulus Before and After Exercise

Brian Head, Justin Busch, Tyler Bies

CU Boulder, Fall 2007

         A study conducted by the department of human physiology at the University of Brussels found that physical exercise influences neurotransmitters in the brain3. It is also known that exercise increases blood flow and oxygen levels throughout the body.  Our experiment was designed to test whether these physiological changes had any effect on reaction times. Reactions can be thought of as an information pathway: information is received by a sense, in this case visual, and is immediately sent to the brain where it is processed.  Then an appropriate response signal is sent via neurological pathway to the muscles causing a reaction. For this experiment it is presumed that physiological changes in the brain caused by exercise are indicated by a raised heart rate1. We hypothesized that the physiological changes induced by exercise would have an effect on reaction times.

            We selected 5 different subjects who were college-aged (18-25) and in visibly good health. For each trial, the subjects reacted to 10 random lights, before and after exercise, by pressing the button that corresponded to the appropriate light stimulus. To limit some variation all subjects were instructed to place their hand on the table rather than Reaction Timer (RT) prior to the stimuli. The mode of exercise used to increase blood pressure was 20 consecutive jumping jacks. To confirm that physiological changes had indeed taken place, we measured heart rate in Beats per Minute (BPM) before and after exercise.

            The results of our experiment showed that the reaction time after exercise (mean = 0.498 seconds) was significantly shorter than the reaction time before exercise (mean = 0.545 seconds); (t = 2.242, P = .0114 < .05).

            After comparing both means we found that they were statistically different, and thus support for our hypothesis. However, a problem with our experiment may have been caused by using random lights. Through experimentation, it became apparent that sometimes the subject missed the light that he/she was reaching for, resulting in an inflated reaction time. In other words, hand-eye coordination was being tested along with reaction times. The best way to fix this problem would have been to use only one light, and let the subject rest his/her finger on the button, thus eliminating the hand-eye coordination variable. While there were no other experiments that resembled ours on the CABLE web site, a study by Sanchez et al.2 , confirmed our results by showing a significant decrease in reaction times with exercise. It is clear that reaction times are improved by exercise, but do they directly correlate to better choices made by an athlete? For example, does a NFL running back make better choices because his reaction times are decreased? Are the faster reaction times a benefit or a detriment to his choices, directions, or routes to the end zone? This is no doubt an intriguing question for sports sciences and would offer a compelling area for further study.

1.              Filipovsky J, Ducimetiere P, Safar ME: Prognostic significance of exercise     blood pressure and heart rate in middle-aged men. Hypertension 1992,         20:333–339

2.              Shanchez X, Barnes K.J., Jones M.A.: The effect of exercise intensity on        visual choice reaction times performances.(Part V. psychology).       Journal of Sports Sciences. Feb 2005, 23.2:156


3.              Mueensen R, Meirleir K: Exercise and Brain Neurotransmission. Journal

Of Sports Medicine. Sep 1995, 3:160-188