The Effect of Aerobic Exercise on Human (Homo sapien) Short-Term Memory
Yousif Astarabadi and Hannah Ogren
Department of Biological Science
Saddleback College
Mission Viejo, CA 92692
Blood glucose has been shown to have a great impact on the enhancement of short term memory in humans. In this study, glucose was used as a variable to test the hypothesis; short term memory will increase after aerobic exercise. The hypothesis that exercise increases short-term memory was assessed by testing subjects with a short term memory test, each before and after exercise, recording the amount of number sequences they recalled before and after exercise. By measuring glucose as a variable, the investigators were able to test blood glucose levels of the participants before and after taking memory tests; both, before and after exercising. The average number of number sets remembered in the initial memory test prior to exercise was 4.6 ± 0.476 (±SEM, n=10) and 7.3 ± 1.27 (±SEM, n=10) in the post exercise memory test.A one tailed, paired t-test revealed that the number of sets remembered after exercise is significantly greater than without exercise (p=0.003). The average blood glucose level in the first blood glucose test was 86.6 ± 3.1 mg/dL (±SEM, n=10), 89 ± 3.7 mg/dL (±SEM, n=10) in the second test, 95.8 ± 6.1 mg/dL (±SEM, n=10) in the third test and 86.6 ± 4.1 mg/dL (±SEM, n=10) in the final test. An ANOVA test revealed that there was no significance in the differences between the glucose levels (p=0.417). There was significant evidence to support the claim that exercise increases short-term memory in humans.
Introduction:
Whether it is doing homework, studying, or taking a test, many news outlets report that students should exercise because it will boost their concentration, memory, and performance on everyday school tasks. Short term memory is the ability to retain a small amount of information for a brief period of time. This can be important in studying because it allows one to access the learned information while still allowing them to input new information. This study will investigate whether exercise will have a significant impact on short term memory.
One reason that exercise is believed to increase short term memory is due to the fact that exercise naturally increases blood glucose levels. Wahren et al, confirmed this in their study by finding that “peripheral glucose utilization increases in exercise despite a reduction in circulating insulin levels…” In fact, a study conducted by Colombani et al (1996), found in their placebo test that glucose levels increase after exercise. And “glucose… can improve aspects of cognitive performance…” (Scholey et al. 2004) Therefore, by having the subjects exercise before taking a test, the results should show that there was an increase in short term memory.
In order to prove that memory increased the subjects had to take a test and see if their results increased after exercise. When a memory test was conducted by Benton and Owens, the results were as follows. “There was a significant correlation between blood glucose values and the number of words recalled. Those whose blood glucose levels were increasing remembered
significantly more words than those whose blood glucose levels were falling.” This proves that the glucose had a significant impact on the test outcomes.
Materials and Methods:
The study was done on November, 7, 2009, at 10:30 am. The study was preformed in Laguna Niguel, California. Ten participants were used in this study,five male and five female, ages eighteen to twenty-two. They were chosen based on their GPA’s of the previous semester and their current study habits. All of the participants fasted prior to participating and all of the participants were hydrated before the study was started.
During this study, the participants took an initial memory test with out having exercised or eaten prior. Their blood glucose levels were taken and recorded prior to the start of the memory test with a Bayer One Touch Glucose Monitor. The area where the blood was taken from was first sterilized with an alcohol wipe. The first drop of blood was wiped away with a cotton ball to prevent contamination. The memory test consisted of a random number sequence of twenty numbers, between two and four digits in length, and was generated from a random number generator. The participants had five minutes to memorize the test, and after they finished studying they waited for five minutes and then wrote down as many numbers as they could recall for four minutes. After the test was taken the participants blood glucose levels were retested in the same manner and the results were then recorded in the lab notebook.
After the first portion of the study, the participants waited for five minutes before beginning the treadmill portion. During this portion the participants jogged for fifteen minutes on the treadmill, at a speed of 7.1 kilometers per hour. They then waited for five minutes and had their glucose levels retested. The participants then took a different memory test with the same format, and studying time. After the participants wrote down as many numbers as they could recall, their blood glucose levels were retested and recorded.
Results:
Memory Tests
The average amount of number sets remembered after exercise was significantly greater than the initial test prior to exercise. The average number of number sets remembered in the initial test prior to exercise was 4.6 ± 0.476 (±SEM, n=10). The average number of number sets remembered after exercise was 7.3 ± 1.27 (±SEM, n=10). A one tailed, paired t-test revealed that the number of sets remembered after exercise is significantly greater than without exercise (p=0.003)(Figure 1).
Blood Glucose Levels
The blood glucose levels did not change significantly throughout the testing period. The average blood glucose level before the initial memory test was 86.6 ± 3.1 mg/dL (±SEM, n=10). The average blood glucose level after the initial memory test and before exercise was 89 ± 3.7 mg/dL (±SEM, n=10). The average blood glucose level after exercise and before the second memory test was 95.8 ± 6.1 mg/dL (±SEM, n=10). The average blood glucose level at the completion of the experiment, after the second memory test, was 86.6 ± 4.1 mg/dL (±SEM, n=10). An ANOVA test revealed that there was no significance in the differences between the glucose levels (p=0.417)(Figure 2).
Figure 1: The average number of sets remembered after exercise are 58.6 percent greater than before exercise. A one tailed, paired t-test revealed that the number of sets remembered after exercise is significantly greater than without exercise (p=0.003).
Figure 2:Between all four glucose tests there was no difference in average blood glucose levels. An ANOVA test revealed that there was no significance in the differences between the glucose levels (p=0.417)
Discussion:
The overall outcome shows that exercising before a task that requires concentration and memorization will indeed increase memory on the participating subject. There was a significant difference between the pre-exercise memory test and the post-exercise memory test (Paired T-test). This conclusion came from extensive study on the effects of exercise on memorization in participants.
Blood glucose levels in participants did not significantly change throughout the experiment at the four glucose test points (four-way ANOVA test). These results conflict with those found by Wahren, Felig and Ahlborg, which stated that blood glucose levels increase significantly after exercise (1974). This could be possible due to the fact that in order to perform a glucose test, the participant must be pricked with a lancet to have access to the blood. This can cause some discomfort in the participants, as well as cause them to be nervous or stressed. Korol, and Gold found in their study that memory can be enhanced through the release of epinephrine, which can be released in subjects when they are stressed. And since the subjects being tested fit in to this category, this could explain the findings.
Also, it is possible that with a more stressful exercise test, that blood glucose would increase more significantly due to glucose being released by the liver because of stress.
Due to the results, there is no evidence from this study that supports the connection between blood glucose and memorization. However, the study does suggest that exercise increases memorization. There are many factors involved that may link exercise and memorization such as: increased blood flow which would bring more oxygen to the brain, epinephrine production during exercise which would increase alertness, and various hormone productions during exercise. The results of the current study, due to the significance shown in an increase of memory due to exercise, suggest that this is an area of study that would greatly benefit from further research.
Acknowledgements:
The investigators in this study would like to acknowledge Dee Conger jr. for his donation of a Bayer One Touch Glucose Monitor, test strips, and lancets. They would also like to acknowledge the Astarabadi’s for use of their treadmill. In addition, the investigators thank Pavilions Pharmacy for donation of test strips and alcohol wipes. Finally, the investigators would like to thank the participants of the study for their time and patience.
References:
Benton, David and Owens, Sarah S. 1993. Blood glucose and human memory. Psychopharmacology 113:83-88.
Colombani, Paolo; Wenk, Caspar; Kunz, Iris; Krahenbuhl, Stephan and Kuhnt, Martina. Arnold, Myrtha. Frey-Rindova, Petra. Frey, Walter. Langhans, Wolfgang. 1996. Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double blind crossover field study. European Journal of Applied Physiology73: 434-439.
Korol, Donna L and Gold, Paul E. 1998. Glucose, memory, and aging. American Journal of Clinical Nutrition 67: 764S-771S.
Scholey, Andrew B, and Kennedy, David O. 2004. Cognitive and physiological effects of an “energy drink”:an evaluation of the whole drink and of glucose, caffeine and herbal flavouring fractions. Psychopharmacology 176: 320–330.
Wahren, John; Felig, Philip and Ahlborg, Gunvor. 1971. Glucose Metabolism during Leg Exercise in Man. The Journal of Clinical investigation 50: 2715-2725.