THE EFFECT OF SINGLE BOUT OF ACUTE EXERCISE ON WORKING MEMORY PERFORMANCE Affiliation

Results The percentage correctness of 2n back task of working memory was found to be 64.36% for baseline res ng condi on, 78.01 % for immediately a er 3-minute step test and 80.70% for 5 minute a er the exercise. In both exercise session (i.e. immediately a er exercise and a er 5 minute of exercise), significant improvement (p value <0.05) in working memory was seen as compared to the baseline res ng session while no such significant beneficial improvement was seen when compared between immediately a er exercise and a er 5 minute of exercise.


Objec ve
The goal of the present research was to study the outcome of single bout of acute moderate-intensity exercise on working memory.

Methodology
Twenty two male subjects were asked to perform working memory task by 2n back task in baseline res ng, immediately a er exercise and a er five minute of exercise session.3 minute step test procedure was used as a moderate intensity exercise interven on.

Results
The percentage correctness of 2n back task of working memory was found to be 64.36% for baseline res ng condi on, 78.01 % for immediately a er 3-minute step test and 80.70% for 5 minute a er the exercise.In both exercise session (i.e.immediately a er exercise and a er 5 minute of exercise), significant improvement (p value <0.05) in working memory was seen as compared to the baseline res ng session while no such significant beneficial improvement was seen when compared between immediately a er exercise and a er 5 minute of exercise.

INTRODUCTION
Retaining op mum brain well-being and func on all over life is a key goal of public health.Extensive research establishes that exercise and fitness are neuroprotec ve 1 and employ a progressive influence on cogni ve func on.Cogni ve func on is the intellectual ac vity that comprises mental processes like learning and memory, a en on, processing speed, execu ve func on and working memory.Working memory includes short-term storage and handling of informa on, expected essen al for an extensive range of complex cogni ve events.Working memory is supposed to play an important role in numerous cogni ve processes and other characteris cs of execu ve func on.Deficits in working memory will extremely impair decision-making 2 process, learning and memory.As a result, working memory has fascinated growing research a en on and has become a center of recent research.
The effect of exercise on different realms of cogni ve func on con nue as vigorously explored area in scien fic research like cogni ve neuroscience, sports science and 3 many other fields.Past analysis shows that long term par cipa on in physical exercise is allied with be er a en on, cogni on and memory; though the outcomes are unreliable when working memory is related to single bout of acute exercise with few studies presen ng favorable effects, no effects, or even nega ve effects.The outcomes differed with form of memory, exercise strength and the 4 extent of exercise.There are different measures available to assess the working memory out of which 2n back task is extensively used in cogni ve func on research as a gold standard measure.Therefore, the present study makes an effort to replicate the previous studies in our popula on and laboratory setup and to correlate the effect of acute moderate-intensity single bout exercise on working memory performance using 2n back task.

METHODOLOGY:
Par cipants: Twenty two medical students of Birat Medical College and Teaching Hospital (mean age = 23.35 ± 1.42 years) were recruited in the study.Informed consent was taken from all the contestants before the experimental protocol.An inclusion criterion was assessed through a detailed history to conform that there was no any poten al risk of cardiovascular, respiratory and other health related disorders in the par cipants to perform a single bout of aerobic acute moderate intensity exercise and working memory task.This study was conducted in Department of Physiology, Birat Medical College and Teaching Hospital from dura on of February, 2017 to July, 2017.

Acute Aerobic Exercise Protocol
The subjects were asked to perform 3 minutes step test on bench of 12-inch height for three minutes in up-up and down-down fashion at the rate of 96 steps per minute.
The test was demonstrated to the subject with alterna ng stepping rhythm.The rhythm of stepping with the beat was carried as follows: step one foot up on the bench (1 beat), step up with the second foot (2ⁿ beat), step down with one foot (3 beat), and step down with the other foot (4 beat.) The subject was asked to prac ce the stepping on the metronome rhythm, which was set at 96 beats per minute (4 clicks = one step cycle) for a stepping rate of 24 steps per minute.The subjects stepped up and down on the pla orm at the given rate for a total of 3 minutes.Immediately a er 3 minute of exercise the subject was asked to stop and sit down and remain s ll.

Working Memory Task
The n-back test is an uninterrupted performance test that is frequently used as a valua on in cogni ve neuroscience to measure working memory and working memory capacity.The subject comes across with a sequence of s muli, with the task consis ng of indica on when the current s mulus matches the one from n steps earlier in the sequence.The s muli factor n can be adjusted to make the task less or more challenging.For example, 1n-back one has to remember the posi on of the item, one turn back likewise 2n-back means that one has to remember the posi on of the item two turns back, and so on.
In our present study, 2n-back test was performed to assess working memory task using www.cognivefun.netprogram.In this task, ten pictures (e.g., car, cake, cat, fish, ball, book heart, shape, pencil, boot, and spoon) appeared on the computer screen randomly and par cipants were asked to click on the target box when the current picture was a repeat of what they had seen or picked 2 pictures ago.Therefore, the target had to be hit if the same picture was repeated in the third place as shown in figure 1.A er end of the task, results with correct percentage were displayed.Each 2n back working memory task was of sixty second dura on where around 32 items were displayed.

Experimental Procedure
A er obtaining informed wri en consent, the subject's informa on regarding history and anthropometric data was recorded in the structured performa.The subject was then instructed for complete bed rest for five minutes to get accustomed to the laboratory environment.A er all paperwork, 2n-back task training for assessment of working memory was done for every subject repeatedly for mul ple number of mes ll the maximum percentage of correctness was a ained during res ng.This was done to exclude the learning effect on working memory performance.It was noted that the subjects understood 2n-back task well.Now, in the formal experiment, the subject was asked to perform first round of working memory task in baseline res ng session.The percentage correctness of the 2n-back test was noted.It was followed with the exercise session by 3 minute step test at the rate of 96 steps per minute and immediately a er the exercise session second round of working memory task was performed.Again, the percentage correctness of 2n-back test was recorded.Then at last, the subject was asked to sit idle for 5 minutes and then the next third round of working memory task was performed.Final recording of percentage correctness was noted.All the subjects' heart rates were recorded during baseline res ng session, immediately a er exercise and 5 minutes a er the exercise session.

Sta s cal analysis
To compare working memory performance differences between baseline and post-exercise sessions, a paired t-test was used to for tes ng the significance.The alpha value was set to 0.05 for the difference to be sta s cally significant.The working memory performance was also correlated with age, gender, BMI or the academic level of the subjects using Spearman's correla on.The sta s cal analysis was done using Sta s cal Package for the Social Sciences (SPSS).

Exercise Intensity
The baseline res ng and exercise session heart rate was 38.12 % and 70.42%, respec vely, of the projected maximal heart rate.The differences in percentage of heart rate during baseline res ng session and exercise session of the projected maximal heart rate recommends the 3 minute step test to be a moderate-intensity exercise.The heart rate of subject a er 5 minute of exercise was found to be returned to that of the baseline res ng condi on.

Working Memory Performance:
Figure 2 presents detailed working memory performance based on the three sessions of 2n back task with exercise interven on.To explore the working memory performance difference between baseline and exercise sessions, a paired t-test was used to for the test of significance.The percentage correctness of 2n back task of working memory was found to be 64.36% for baseline res ng condi on, 78.01 % for immediately a er 3-minute step test and 80.70% for 5 minute a er the exercise.The both exercise session (i.e.immediately a er exercise and a er 5 minute of exercise) showed significant improvement (p value <0.05) in working memory as compared to the baseline res ng session while no such significant beneficial improvement was seen when compared between immediately a er exercise and a er 5 minute of exercise.The working memory performance in our study did not significantly differ in respect to age, gender, BMI or the academic level from which the subjects were enrolled.

DISCUSSION
This research studied the impacts of single bout of acute moderate exercise on working memory performance.The exercise session was correlated to a baseline session of working memory.It was hypothesized that an associa on would be present between those parameters, and the current study supported this hypothesis.The core finding of our study was that even a very short period of three minute moderate intensity exercise test is good enough to a ain posi ve impact on working memory.An increasing bulk of literature by Erickson  Visual Memory Span tasks of Wechsler Memory Scale.In our study, we concluded that working memory performance is enhanced with 3 minute of moderate intensity exercise.Through, a series of literature review we could not find sa sfactory result on the op mum intensity and dura on of exercise which a ains a peak level of enhanced working memory performance as it is noted that even increase in the dura on and intensity of the exercise more than op mum level would decrease the working memory performance.Therefore, we feel that further study needs to be carried out in this direc on.
The exact neurophysiological mechanism that is affected by acute exercise is s ll unknown but it is es mated that exercise may intensify the courses of neuroplas city at 12 molecular and cellular level.Thus, further work in future is an cipated to explicate the specific mechanisms by which the exercise affects the human cogni on.Few studies argue that the changes in the working memory performance is es mated due to enhanced ac vi es of the brain including bilateral parietal cor ces, le hippocampus, and the 13 bilateral cerebellum elicited by acute aerobic exercise.Also, exercise-induced varia on in regional cerebral blood flow has also been proposed as a probable mechanism for 14 increased cogni on level.Some studies also states that rise in central and peripheral accessibility of neurotrophic elements, energy substrates and signaling molecules are 15 reason behind beneficial memory performance.Some researchers using animal model have revealed that exercise Original Research Article shows beneficial influence on cogni ve func on because it brings some changes in brain structure such as hippocampus 16,17 and cerebral cortex.

CONCLUSION
The current findings support our hypothesis that moderate intensity exercise is related to improve processing task that assessed working memory performance in healthy young adults.It also suggests that acute bouts of exercise may be tremendously useful for those whose cogni ve performance is low.Thus it is concluded that even single bout of acute exercise has beneficial effect on working memory and ul mately overall cogni ve func on.Therefore, acute exercise can be important in decision making, learning and memory process.

RECOMMENDATIONS
We found that even three minute of acute exercise improves working memory and cogni ve func on.Therefore, it is recommended to develop moderate exercise as a daily habit to all age groups to boost memory, improve concentra on, improve mental health, enhance crea vity and retard cogni ve decline with age.

LIMITATIONS OF STUDY
The present research is not devoid of limita ons.The overview of our results is constricted by less number of sample sizes.Further research in future with greater number of sample size might be more reliable to explore the result of acute single bout exercise on working memory.Also, in the experimental procedure, we es mated working memory performance only up to five minutes of exercise, therefore, we could not follow up the me limit up to which the significant beneficial effects of acute exercise exists.Likewise, besides n-back task, even other different measures of working memory capacity like complex span tasks (C span), working memory upda ng tasks (Upda ng) and tasks of temporary bindings (Binding) could have been tested simultaneously to increase the reliability of the working memory performance.

Figure 2 :
Figure 2: Change in percentage correctness of 2n back text in rela on to exercise interven on.The percentage correctness of 2n back task of working memory was found to be 64.36% for baseline res ng condi on, 78.01 % for immediately a er 3-minute step test and 80.70% for 5 minute a er the exercise.The both exercise session (i.e.immediately a er exercise and a er 5 minute of exercise) showed significant improvement KI et al, Chang YK et al. and Drolle e ES et al shows that acute aerobic exercise improves working memory performance and our results are also in agreement 6-8 with these previous research findings.Similarly, a study by Hillman et al revealed that an acute treadmill workout was correlated to improved working memory performance while carrying out a visual a en on task by Eriksen flanker 9 test.Also, a study by Sibley et al revealed that acute exercise of moderate-intensity on a treadmill led to enhanced Stroop test performance which is one of the important measure of 10 cogni ve func on.A similar study by Simazach et al revealed that volleyball training interven ons increased the working memory performance measured by Digit span and 11