'Effects of Exercise Intensity and Duration on Working Memory Capacity'

Omar Matoo 313SPO – Psychology Dissertation Word Count: 5257

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THE EFFECTS OF EXERCISE INTENSITY

AND DURATION ON WORKING MEMORY

CAPACITY

OMAR MATOO

A report published in the Faculty of Health and Life Sciences, Coventry

University, towards the degree of Bachelor of Science with Honours in

Sport and Exercise Science, March 2014


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CONTENTS

1. Abstract…………………………………………………………………….. ..page 4

2. Introduction…………………………………………………………………..page 5

3. Aims, Objective and Hypotheses………………………………………….....page 10

3.1. Aims……………………………………………………....page 10

3.2.Objectives……………………………………………….....page 10

3.3.Hypotheses……………………………………………........page 11

4. Materials and Methods…………………………………………………….....page 12

4.1. Participants………………………………………………..page 12

4.2. Measures………………………………………………….page 13

4.2.1. Physiological………………………..page 13

4.2.2. Psychological……………………….page 14

4.3. Procedure………………………………………………....page 14

4.4. Testing Period………………………………………….....page 15

4.4.1. Pilot Study…………………………..page 15

4.4.2. Session 1…………………………….page 15

4.4.3. Session 2…………………………….page 16

4.5. Statistical Analysis……………………………………….page 17

5. Results……………………………………………………………………….page 18

6. Discussion…………………………………………………………………...page 26

7. Conclusion…………………………………………………………………...page 32

8. Limitations and Suggestions for Further Work……………………………...page 34

9. References…………………………………………………………………...page 37

10. Appendices…………………………………………………………………..page 39

11. Acknowledgements………………………………………………………….page 44


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TABLES AND FIGURES

Tables

4.1 - Descriptive results of mean group WM scores across exercise intensities and

testing conditions……………………………………………………………..page 21

4.2 – Descriptive results of mean group WM score differences between B – IAE and B

– R testing conditions across exercise intensities…………………………….page 21

FIGURES

4.1 - Mean WM scores across exercise intensities and test conditions………page 22

4.2 - Mean WM score differences between B - IAE and B – R testing conditions across

exercise intensities……………………………………………………………page 23

4.3 - Individual WM test scores for 50% HRR exercise protocol…………...page 24

4.4 - Individual WM test scores for 90% HRR exercise protocol……………page 25


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1. ABSTRACT

Working memory (WM) is the ability to temporarily store and recall information (Baddeley,

1992). In regards to sports psychology, effects of submaximal intensity and high intensity

exercise have been investigated (Coles and Tomporowski, 2008; McMorris et al. 2011;

Sibley and Beilock, 2007; Dustman et al. 1984) to find if these have any significant effects on

WM capacity. Working memory is assessed using a number of methods, including the Digit

Span test (Weschler, 1945).This study aimed to investigate the effects of acute bouts of

aerobic exercise undertaken at 50% heart rate reserve (HRR) and 90% HRR on WM capacity

in a group of twelve male Coventry University Team Phoenix football players. Each

participant completed baseline Digit Span tests, succeeded by a two-minute period of

exercise at respective exercise intensities on treadmill apparatus (h/p/cosmos Mercury

treadmill and Woodway treadmill). Ratings of perceived exertion (RPE) (Borg, 1998) were

taken alongside heart rate (HR) as secondary measures of physical exertion. Digit Span tests

were administered following exercise cessation and again following a 20-minute recovery

period. Repeated-measures ANOVA and Tukey post-hoc statistical analysis tests were

performed to determine where any significant statistical differences lay within the dataset (P

< 0.05). Working memory test scores improved across exercise intensity and durations, but

statistical analysis demonstrated that such changes were statistically insignificant for 90%

HRR testing protocol as opposed to50% HRR. Further research should be focussed on

looking into the effects of high exercise intensity on WM capacity in more detail so as to find

conclusive evidence of such effects. The present study supports the findings of current

literature regarding the effects of moderate intensity exercise on WM capacity.


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2. INTRODUCTION

The concept of working memory (WM), which is the ability to temporarily store and recall

information, has evolved from the idea that an exclusive unitary short-term memory

system exists for the processing of information that is necessary for learning and reasoning

(Baddeley, 1992). This is especially true for the acquisition of language (Gathercole and

Baddeley, 1993), where working memory was found to influence the development of

vocabulary, and both verbal and physical action (Baddeley 2007). However, the ability for

individuals to utilise working memory suffers from a limited capacity, which means that

information can only be stored for short periods of time (Baddeley and Hitch, 1975). A three-

dimensional model outlining the components of WM was created by Baddeley and Hitch

(1975). This model consists of the phonological loop (information received and retained

through sound, constantly refreshed cognitively through the individual’s ability to remember

the information given), the visuo-spatial sketchpad (information taken in and retained

visually) and the episodic buffer, which integrates the former two components, but can

additionally store and retain information these components cannot, such as rhythm. These

three components are supervised by the central executive, which delegates information to

these components (Baddeley and Hitch, 1975; D’Esposito et al. 1995).


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Working memory can be assessed using a number of different cognitive tests, one of which is

the Digit Span test (Wechsler, 1945). However, as WM capacity is limited, research has been

undertaken in order to find interventions which can be used to enhance this function.

In the context of sport psychology, WM capacity has been researched with relation to how

exercise affects an individuals’ ability to utilise WM (Pontifex et al. 2009; Sibley and

Beilock, 2007). It has been believed that physical activity has a beneficial impact on WM

performance and capacity (Coles and Tomporowski, 2008; Pesce et al. 2009; McMorris et al.

2011; Sibley and Beilock, 2007; Dustman et al. 1984)). For example, Dustman et al. (1984)

investigated the effect of an aerobic exercise training programme implemented over a four

month period within sedentary 55-70 year old individuals. Working memory was assessed

using a neuropsychological test battery, consisting of a series of Digit Span tests. Compared

with a control group, aerobically trained individuals demonstrated an improvement after

exercise on baseline Digit Span scores, thus indicating that exercise has an enhancing effect

on WM (Dustman et al. 1984). Although this study provides a basis that there is a beneficial

effect of aerobic exercise on WM capacity, the study does not account for effects on younger

adults and children. Therefore, the study cannot be generalised to a younger population. It is

important, then, that literature related to the effects of aerobic exercise on WM capacity in


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younger adults is considered also.

Sibley and Beilock (2007) aimed to analyse the effects of exercise on WM using 48

undergraduate American college students. The participants were subjected to baseline

exercise sessions, with the main testing session administered one week after. Exercise was

conducted using treadmill apparatus, in which the participants engaged in maximal intensity

training. Following exercise, the participants were then administered with WM tests. From

the results attained, the participants were split into four quartiles: high WM, middle-high

WM, middle-low WM and low WM groups. The results demonstrated that the use of a

VO2max exercise session preceding WM tests significantly improved results of the low WM

group (P < 0.01), with mean WM test scores rising from 24 to 28. For the other three groups,

however, no such enhancement was seen (P = 0.48). It was concluded, therefore, that

exercise is beneficial to WM function for those with an initial low capacity to utilise working

memory, thus providing a basis that individual difference is a key factor in determining how

efficient exercise is in enhancing WM capacity.

An additional study by Pontifex et al. (2009) investigated the effects of three different

modes of exercise (acute aerobic exercise [VO2max], acute moderate aerobic exercise and


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acute resistance training) on WM capacity of 21 undergraduate students. Pontifex and

colleagues administered a modified version of the Digit Span test, known as the Sternberg

task (Sternberg, 1966), which uses letters in place of numbers, before, immediately after and

30-minutes following exercise for each training condition to compare differences in result

variance. Results revealed that WM test results following acute aerobic VO2max exercise bouts

were significantly lower when compared with results from baseline tests. Working memory

tests administered following acute bouts of resistance training had no significant effect on

results, whereas following moderate intensity aerobic exercise bouts seemed to enhance WM

capacity, improving results compared to baseline administration. Pontifex et al. (2009) thus

conclude that a pivotal factor that determines the ability to utilise WM effectively, and in

some cases to enhance WM performance, is the type of exercise that is undertaken.

Furthermore, the results also seem to indicate that exercise intensity may also be a key factor.

As can be seen, maximal aerobic training and resistance training, which are forms of high

intensity training, were responsible for drastic decreases in WM test scores (Pontifex et al.

2009). Moderate aerobic exercise, on the other hand, facilitated an improvement in WM

performance and capacity, which supports the findings of the studies mentioned previously

(Dustman et al. 1984; Sibley and Beilock, 2007). However, differences in WM test scores as

a result of changes in exercise intensity were found to be less significant (P > 0.05) than the


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effect that mode of exercise had on WM capacity (Pontifex et al. 2009), and consequently

further research is required in this area. This study will be undertaken in with the aim of

expanding on the current literature with relation to whether exercise intensity does have a

significant effect on WM capacity.


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3. AIMS, OBJECTIVES & HYPOTHESES

3.1 Aim

The aim of this study was to investigate the effects of two different exercise intensities (50%

heart rate reserve [HRR] and 90% HRR) on WM capacity.

3.2 Objectives

To measure heart rate reserve (HRR) during rest, and to monitor changes of

resting HRR during exercise for both intensities.

To assess WM capacity using the Digit Span (Weschler, 1945) test before exercise,

immediately after exercise and following a 20 minute recovery period succeeding

exercise.

To perform statistical analysis of results to see if any differences that exist from

exercise on WM test scores are significant.


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3.3 Hypotheses

Hypothesis 1: Acute moderate-intensity aerobic exercise (50% HRR) will increase

WM capacity immediately after exercise and following a 20 minute recovery period.

Hypothesis 2: Exercise undertaken at 90% HRR will decrease WM capacity

immediately after exercise, but not after a 20 minute recovery period.


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4. MATERIALS & METHODS

4.1 Participants

Fifteen male footballers (n = 18-24 years old; mean age = 20 ± 1.48 years) who are members

of the Coventry University Team Phoenix football club were recruited. All participants were

recruited via the president of the football club, a formal collaborator within the project. Prior

to experimentation and in keeping with the ethics policy set by Coventry University, consent

forms (see Appendix 2) and Standard Departmental Health Screen forms (see Appendix 4)

were signed by each participant to ensure suitability for testing; in addition, these documents

were approved by a moderator. Participants were notified of the nature of the study via

participant information sheets and verbal instruction, and were made aware that they had the

right to withdraw from participation. An ethics form was completed, sent to and authorised

by the Coventry University Ethics Committee,

As this study involved the use of treadmill apparatus, physical harm and injury posed a

potential danger. In order to avoid unnecessary injury or accidents, participants were briefed

on how to use the equipment properly at the beginning of each session.


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4.2 Measures

4.2.1 Physiological

Heart rate reserve (HRR) is the difference between an individuals’ predicted maximal heart

rate and their resting heart rate (Swain and Leutholtz, 1997). This was calculated for each

subject for both exercise protocols using the following equation:

220 – age – resting heart rate (RHR) x (HRR percentage) + RHR (Tanaka, Monahan and

Seals, 2001).

Polar heart rate monitor apparatus was used to track HR. Changes in these readings were

monitored during and after exercise in order to observe the effect that exercise on HRR had

on working memory capacity.

Ratings of perceived exertion (RPE) are used as an indicator of physical activity intensity,

and according to Borg (1998), RPE values serve as an estimate of heart rate during physical

activity, and so may correlate with changes in HRR that may be demonstrated during

exercise. RPE was measured using the Borg scale, which incorporates a scale of 6 (no

exertion) to 20 (maximal exertion) (Borg, 1998).


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4.2.2 Psychological

Working memory capacity was assessed using the Digit Span test (Wechsler, 1945) (see

Appendix 3). This test involves reading out a sequence of three, five or seven numbers

consecutively, which the participant would attempt to remember and recite thirty seconds

following the recollection phase. Each number sequence condition consisted of two trials (see

Appendix 3). Following an incorrect recitation of one number sequence trial, WM test

administration ceased.

4.3 Procedure

The study was undertaken in a laboratory setting. To ensure the environment was suitable for

testing, the laboratory was checked for hazards prior to each session. Health screen checks

(see Appendix 4) were performed on each participant to ensure suitability for

experimentation. The study involved each participant partaking in two separate sessions, each

following different protocols so that the effects of exercise intensity and duration on WM

capacity could be seen across two separate trial conditions.


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4.4 Testing Period

4.4.1 Pilot Study

A pilot study was conducted one week prior to the commencement of the testing period for

familiarisation of equipment handling and usage, and protocol administration. One member

of the research group undertook 90% HRR testing protocol. Problems were experienced with

Polar heart monitor apparatus. This was promptly addressed in order to avoid similar

occurrences during the course of the data collection period. Pilot studies are seen as an

effective measure in terms of reducing human error as a result of test implementation prior to

undertaking preliminary data collection (Reason, 2000.)

4.4.2 Session 1

Baseline HRR was recorded using Polar heart monitor apparatus. Immediately following

this, a Digit Span test was performed to determine baseline (B) WM capacity. A

two minute period of acute aerobic exercise at 50% HRR aerobic exercise was then

undertaken by participants using treadmill apparatus (h/p/cosmos Mercury treadmill and

Woodway treadmill) . RPE was taken using the Borg scale (Borg, 1998) at every two minute

interval during exercise before 50% HRR was reached, where participants then trained at a

constant intensity for two additional minutes. Immediately after this period (within one

minute following exercise), the Digit Span test was administered (IAE). A final Digit Span


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test was administered following a 20-minute recovery period (RAE).

Prior to the commencement of session 1 testing protocol, three of the 15 participants

withdrew their consent for participation in the study.

4.4.3 Session 2

Baseline Digit Span tests were administered prior to the undertaking of acute aerobic exercise

at 90% HRR. Ratings of perceived exertion, as for the previous session, was taken alongside

HR at every two minute interval of exercise until 90% HRR was reached, where participants

again trained at a constant intensity for an additional two minutes. Digit Span tests were

again, administered following the immediate cessation of exercise, with a final Digit Span

test administration following a 20-minute period of recovery after exercise cessation.


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4.5 Statistical Analysis

Descriptive statistics for means and standard deviations (SD) of group WM scores were

calculated using Microsoft Excel. IBM SPSS Statistics 20 (IBM; New York, USA) was

used to carry out two-way repeated-measures ANOVA tests to determine differences within

WM scores between the two different exercise intensities. Tukey Post-hoc tests were

conducted to determine if any significant statistical differences lay within the data sets in

regards exercise intensity, duration and trial condition.


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5. RESULTS

Descriptive statistics of WM test scores across exercise intensities and test conditions are

displayed in table 4.1, and descriptive statistics mean group score differences across exercise

intensities and testing conditions are displayed in table 4.2. Mean WM test scores across

exercise intensities and test conditions, and the mean test score differences between B and

IAE (B – IAE) conditions and B and RAE conditions (B – RAE) are displayed in figures 4.1

and 4.2 respectively. Individual test scores for 50% HRR exercise protocol and 90% HRR

exercise protocol are displayed in figure 4.3 and figure 4.4 respectively.

Mean group WM test scores across both exercise protocols increased with successive Digit

Span test administrations (see Table 4.1; Figure 4.1). During testing for 50% HRR exercise

protocol, IAE Digit Span test administration resulted in 58% of participants greater WM test

scores in comparison with B WM test scores (see Figure 4.1). Three participants, however,

achieved a lower WM score in the IAE condition as opposed to B during 50% HRR exercise

protocol (see Figure 4.3). Statistically significant mean group WM test scores were observed

between test scores in the B condition and RAE condition (P = 0.001) (see Table 4.1). Test

administration during the RAE condition demonstrated an increase of +2 in mean group WM

test scores in comparison with B WM test administration (see Table 4.1; Table 4.2), with 68%


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of participants achieving a greater WM score in the RAE test administration condition.

Further score improvements were observed between WM tests administered in the RAE

condition as opposed to the IAE condition (see Figure 4.1; Figure 4.2; Figure 4.3). One

participant in the RAE test condition, however, did achieve a lower test score as opposed to

IAE WM test administration (see Figure 4.3).

Working memory test scores at 90% HRR exercise protocol between B and IAE conditions

were higher as opposed to 50% HRR exercise protocol B and IAE WM test scores (see Table

4.1; Figure 4.1; Table 4.2; Figure 4.2), with an increase of +1 for both test conditions. This

increase in mean group WM test scores across the B and IAE test conditions from 50% HRR

testing protocol to 90% HRR testing protocol as a result were statistically significant (P =

0.07). One participant, however, achieved a lower WM score in the IAE condition as opposed

to the B condition (see Figure 4.4). There was a small improvement in WM test scores

between the IAE test condition and the RAE condition (see Table 4.1). Only three subjects

within the R test condition during 90% HRR exercise protocol achieved higher WM test

scores as opposed to B and IAE test conditions. In addition, 90% HRR protocol mean group

WM test score in the RAE condition, interestingly, was significantly lower than 50% HRR

protocol mean group RAE condition WM test score (P = 0.02) (see Table 4.1; Figure 4.1).


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Standard deviation of results across test conditions and exercise intensity protocol were

consistent (see Figure 4.1).

A statistical significance was observed in group means for differences in B - IAE test

scores, and B - RAE test scores (see Table 4.2; Figure 4.2) (P = 0.08). Greatest improvements

in WM test scores across exercise intensities occurred between B - RAE test administrations

(see Figure 4.2). A significant increase in WM test scores between these two conditions were

observed for 50% HRR exercise protocol testing (see Figure 4.1) (P = 0.001). Improvements

in results for these test conditions for 90% HRR exercise protocol testing compared to 50%

HRR were statistically insignificant (P = 0.3). While differences between B – IAE WM test

score differences were exactly the same across both exercise protocols (see Table 4.2; Figure

4.2), the differences between B – RAE WM test scores were significantly higher at 50% HRR

protocol compared with 90% HRR (P = 0.03). (see Table 4.2; Figure 4.2).


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Table 4.1 - Descriptive results of mean group WM scores across exercise intensities and

testing conditions

Table 4.2 – Descriptive results of mean group WM score differences between B – IAE and B

– R testing conditions across exercise intensities

Baseline (B) Immediately after

Exercise (IAE)

20 minutes recovery

(RAE)

50% HRR 7.33 ± 1.78 8.17 ± 2.04 9.33 ± 1.78

90% HRR 8.33 ± 1.87 9.17 ± 1.99 9.25 ± 2.45

B - IAE B - RAE

50% HRR 0.83 ± 1.59 2 ± 0.94

90% HRR 0.83 ± 1.48 0.92 ± 1.24


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0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

Baseline Immediately After

Exercise

20 Minutes Recovery

Mea

n W

M S

core

Test Condition

50%

HRR

90%

HRR

Fig 4.1 Mean WM scores across exercise intensities and test conditions

Data shown as mean ± SD ( = significant value [P = 0.07], = significant value

[P = 0.02]), = significant value [P = 0.001])


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0.00

0.50

1.00

1.50

2.00

2.50

Baseline - Immediately After

Exercise

Baseline - 20 Minute Recovery

WM

Sco

re D

iffe

ren

ces

Condition

50% HRR

90% HRR

Fig 4.2 Mean WM score differences between B - IAE and B – RAE testing conditions across

exercise intensities

Data shown as mean ± SD ( = significant value [P = 0.08], = significant value

[P = 0.03])


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0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

1 2 3 4 5 6 7 8 9 10 11 12

WM

Sco

re

Participant

B

IAE

RAE

Figure 4.3 Individual WM test scores for 50% HRR exercise protocol


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0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

1 2 3 4 5 6 7 8 9 10 11 12

WM

Sco

re

Participant

B

IAE

RAE

Figure 4.4 Individual WM test scores for 90% HRR exercise protocol


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6. DISCUSSION

The aim of the study was to investigate the effect of exercise intensity on WM capacity.

Results demonstrate that mean group WM test scores for B, IAE and RAE test administrations

improved across both testing protocols (see Table 4.1; Table 4.2).

Working memory test administrations for IAE conditions at50% HRR and 90% HRR

testing protocols resulted in greater group mean WM test scores in comparison with B WM

test administration scores. While the results seem to concur with the findings of Pontifex et

al. (2009) with relation to the effects of acute bouts of moderate intensity aerobic exercise,

the findings seem to suggest the contrary in relation to the effects of acute bouts of higher

intensity aerobic exercise as opposed to the findings presented by Pontifex and colleagues. It

is important to note that the sample used by Pontifex et al. (2009) did not consist of athletes,

as was the sample used in this study, but rather undergraduate students. Smith et al. (2010)

observed that aerobically trained individuals as a result of exercise experienced

improvements in attention, processing speed, executive function and memory. Pontifex et al.

(2009) expand on this, stating that aerobic exercise facilitates the release of biochemicals,

such as serotonin, which aids in “neural proliferation”: the development of brain structure and

capacity (Kramer, Erickson and Colcombe, 2006; Wu et al. 2008). In addition, this

phenomena has been reported to occur especially as a result of undertaking exercise on a


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treadmill (Wu et al. 2008). Undertaking acute bouts of aerobic exercise on a cycle ergometer

has been found, in comparison with exercise undertaken on a treadmill, to have a much lesser

beneficial impact on WM capacity (Sibley and Beilock, 2007).Dustman et al. (1984)

supported Smith and colleagues findings, observing that the use of an aerobic exercise

training programme had a significant enhancing effect on WM capacity in a group of

sedentary 55-70 year olds in comparison to a control group. Furthermore, McAllister et al.

(2006) propose that in individuals with high levels of fitness, “executive functions” within the

hippocampus (site of neurogenesis and “neural proliferation”) can be more readily

maintained or enhanced, thus benefiting ability to utilise WM. The study therefore, along

with the findings of Smith et al. (2010), Dustman et al. (1984) and McCallister et al. (2006)

provides a basis that aerobically trained individuals benefit from an enhanced WM capacity

following bouts of acute aerobic exercise at various intensities. The study also demonstrates

that the use of exercise as an intervention in helping to enhance WM capacity does not only

work for the elderly population as shown by Dustman et al. (1984), but can also be used to

help improve WM capacity in young adults.

However, in the present study it was found that across both testing protocols, the highest

group mean WM test scores were achieved in RAE WM test administrations (see Table 4.1).

Significant improvements in group mean WM test scores were observed between these


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conditions for 50% HRR testing protocol (P = 0.001) (see Table 4.1; Figure 4.1), with test

scores increasing by +2 from B – RAE test administrations (see Table 4.2). These results are

supported through research carried out previously in this area (Pontifex et al. 2009), who also

found that bouts of moderate intensity exercise had an enhancing effect on WM capacity. The

results therefore provide evidence that undertaking acute bouts of aerobic exercise at 50%

HRR helped enhance WM capacity as opposed to B WM test administration. In addition,

WM capacity was further enhanced following a recovery period succeeding cessation of

exercise, thus hypothesis 1 can be accepted.

During 90% HRR testing protocol, mean WM group scores for B and IAE Digit Span test

administrations were significantly(P = 0.07) higher than mean group scores at 50%. (see

Figure 4.1) It has been established that aerobically trained athletes experience enhancements

in WM capacity following acute aerobic exercise regardless of the intensity it is undertaken

(Smith et al. 2010; Dustman et al. 1984). In the present study, mean group WM test scores

were again highest for RAE test administration. However, when compared with the change in

scores that occurred between IAE – RAE test administrations across exercise intensities, there

was a much more significant improvement in mean group WM test scores at 50% HRR

compared with 90% HRR (IAE – R test score difference at 50% HRR = +1.16; IAE – RAE

test score difference at 90% HRR = +0.08) (P = 0.02) (see Figure 4.1). Consequently, the


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results of this study demonstrates that recovery only results in significant WM capacity

enhancement when it succeeds an acute bout of exercise at moderate intensity. Although it

was observed that a 20-minute recovery period helped enhance WM capacity following acute

bouts of exercise undertaken at 90% HRR, the contrary was reported in relation to hypothesis

2 regarding the effects of WM capacity immediately following exercise, thus hypothesis 2

can be rejected.

However, the study did not account for possible occurrences of “learning effects” within

participants as a result of not implementing a testing protocol incorporating random

allocation of participants to testing conditions to avoid such effects (Gaito, 1961). It should

also be noted that the number sequences used for the Digit Span test across the two sessions

remained the same for each session, which may have also contributed to the improvement of

WM test scores as a result of “learning effects”, rather than as a result of changes in exercise

intensity and duration. Therefore, in order to truly see if exercise duration and intensity had

an effect on WM capacity, mean group score differences across B – IAE test administrations

and B – RAE test administrations were also analysed.


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Figure 4.2 shows that the difference between B – IAE test administration scores at 50% HRR

and 90% HRR remained the same (0.83), but significant differences can be seen between

50% HRR and 90% HRR for differences in B – RAE WM test administrations. Improvements

in WM scores across B – RAE test administrations at 50% HRR were significantly higher

when compared with WM score differences for B – R test administrations at 90% HRR (P =

0.03) (Figure 4.2). Pesce et al. (2009) compared the effects of submaximal intensity aerobic

circuit training and higher intensity exercise on WM capacity in pre-adolescents, and also

found that while higher intensity exercise did help enhance WM capacity, greater

enhancements were found following the completion of submaximal intensity aerobic circuit

training. It has been reasoned that while aerobic exercise does help enhance WM capacity via

the release of biochemicals promoting neurogenesis, increasing the intensity of aerobic

exercise can have a negative impact, by decreasing brain glucose uptake, forcing the brain to

take in lactate to compensate for this loss (Kemppainen et al. 2005). This occurrence has

been found to significantly hamper the ability to utilise WM, and can continue to occur

following exercise cessation depending on how excessive the rate of brain lactate

accumulation is in relation to rate of brain lactate removal (Dienel and Hertz, 2001; Zhao et

al. 2004). Excessive lactate uptake by the brain has been reported to contribute to the

“abolishment” of WM capacity, and in some cases where this occurrence is prevalent across


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the life course of an individual, can negatively affect long-term memory function, resulting in

the onset of psychological conditions such as amnesia (Suzuki et al. 2011).This may provide

an explanation for why differences between mean WM group score differences between B –

RAE test administrations at 90% HRR were minimal in comparison with the same conditions

at 50% HRR (Figure 4.2). This study, therefore, demonstrates that WM capacity is enhanced

more significantly as a result of recovery following an acute bout of aerobic exercise at 50%

HRR, whereas a recovery period following an acute bout of aerobic exercise at 90% HRR is

has a less significant positive impact on WM capacity. It has been noted, however, that there

is not enough literature focussing on the effects of high intensity exercise on WM capacity,

and thus more research is needed in this area (McMorris et al. 2011).


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7. CONCLUSION

The study investigated the effects of exercise duration and intensity on WM capacity and

performance. In conclusion, WM capacity improved across testing conditions for both

exercise protocols, but a key finding was that improvements in score differences across

testing conditions for 50% HRR testing protocol were more significant than the

improvements seen in WM capacity across testing conditions for 90% HRR testing protocol.

This may be due to the complex physiological interactions of biochemicals and metabolic

changes which occur in the hippocampal region of the brain - an essential component of the

brain with respects the development of brain structure and function (Galea et al. 2000;

McAllister et al. 2006) - as a result of increased exercise intensity. As stated previously,

however, there is a lack of existing literature to support the study’s findings that higher

exercise intensity facilitates a less positive effect on WM capacity as opposed to submaximal

aerobic activity (McMorris et al. 2011). This provides a platform, therefore, for further

research to be undertaken in this area to establish a definitive explanation regarding the

effects of high intensity exercise on WM capacity. The study, along with previous research,

also demonstrates that aerobically trained individuals may benefit from WM enhancement

after aerobic exercise due to enhanced cognitive function (Pontifex et al. 2009; Smith et al.

2010; Dustman et al. 1984; McAllister et al. 2006). It is also significant to note that, as


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previous research focussed heavily on the elderly population, this study provides a degree of

evidence that exercise can also help to facilitate enhancements in WM capacity within

younger adults.

There may be further applications, however, for future research to focus on

the effects that exercise intensity and duration has on older adults in comparison with

younger adults, to determine if there are any age-significant differences to exercise on WM

capacity, rather than just looking at these populations exclusively,


34

8. LIMITATIONS AND SUGGESTIONS FOR FURTHER WORK

The main limitation of this study was that “learning effects” were not taken into account, as a

protocol involving the random allocation of subjects to the two testing protocols was not

implemented (Gaito, 1961). As results centred on the improvement of WM test scores

overtime across testing conditions and exercise protocols may have been negatively

impacted by “learning effects” and the absence of counterbalancing, analysis of mean group

score differences between B –IAE and B – RAE testing conditions across exercise intensities

were also undertaken to determine if exercise duration and intensity had any effect on WM

capacity (Table 4.2). In order to avoid such discrepancies in future, implementation of

“counterbalancing” can be done to ensure participants do not score highly depending on their

ability to remember the task they are undertaking and the sequence of numbers that have been

relayed to them. It may also be possible to implement a blind testing procedure into the

experimental design so that participants are not aware of the trials that they will forego, and

thus cannot anticipate the testing conditions in which they will undertake. An additional

problem linked to those outlined as previous were that the same number sequences were used

across each WM test trial for both exercise protocols. This may have skewed results as a

result of participants remembering the sequence of numbers from previous test

administrations, and so WM scores may have improved regardless of exercise intensity and


35

duration . In order to overcome this, the use of number sequences with different number

patterns may be used to ensure “learning effects” do not have a significant effect on WM

scores as opposed to the independent variables.

Another limitation may have been that on certain days of testing, the participants were due

for training sessions later on in the day and may not have exerted themselves at the

appropriate levels that were required of them in relation to the exercise training protocol. This

may further skew results, as not reaching the necessary training zone, especially in relation to

90% HRR protocol, may have helped them to recall number sequences better than if they had

reached their zone due to lack of mental and physical fatigue. In order to overcome this in

future, it would be wise to change the days and time of the day in which testing commences

for participants. This may not only make it more convenient for participants to be able to

produce more effort during testing, but it may allow participants to do this also by carrying

out testing at a time where their individual Circadian rhythms coincides with the time in

which they are able to produce maximal physical effort (Smith, Guilleminault and Efron,

1997).


36

As highlighted in the conclusion, further research would focus on the effects of high exercise

intensities on WM capacity. From these findings, it could then be concluded whether high

intensity exercise does contribute towards a less effective WM capacity after a period of

recovery as opposed to submaximal exercise intensities. Further research may also be

focussed on the differences between age-specific responses to exercise on WM capacity,

which may expand on the findings from research done looking at age-specific responses

separately.


37

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39

10. APPENDICES

Appendix 1 Raw data

Partici

pant

Rest

ing

Hea

rt

Rate

(RH

R)

50%

Hea

rt

Rate

Rese

rve

(HR

R)

Digit

Span

Test

Score

(Basel

ine)

diffBL_to_imm

ediate_50

Digit

Span

Test

Score

(Immed

iately

After

Exercis

e)

diffBL_to_3

0min_50

Digit

Span

Test

Score

(30

Min.

Recov

ery)

90%

Hea

rt

Rate

Rese

rve

(HR

R)

Digit

Span

Test

Score

(Basel

ine)

DiffBL_to_im

mediate90

Digit

Span

Test

Score

(Immed

iately

After

Exercis

e)

diffBL_to3

0min90

Digit

Span

Test

Score

(30

Min.

Recov

ery)

1 85 142 6 0 6 1 7 188 6 0 6 0 6

2 75 138 5 3 8 3 8 185 7 1 8 0 7

3 115 159 6 -2 4 0 6 193 6 0 6 -1 5

4 90 145 6 1 7 3 9 189 6 2 8 2 8

5 96 148 10 0 10 0 10 190 10 1 11 1 11

6 78 140 6 2 8 3 9 189 9 1 10 1 10

7 88 143 8 2 10 3 11 187 11 1 12 3 14

8 63 131 11 -1 10 0 11 185 9 1 10 1 10

9 85 143 8 2 10 3 11 189 11 0 11 0 11

10 75 137 7 -1 6 4 11 186 7 2 9 3 10

11 73 138 7 2 9 1 8 189 9 2 11 0 9

12 86 143 8 2 10 3 11 189 9 -1 8 1 10


40

INFORMED CONSENT FORM

UNDERGRADUATE AND TAUGHT POST GRADUATE STUDENT PROJECTS

DEPARTMENT OF BIOMOLECULAR AND SPORT SCIENCES

“The effects of exercise intensity and duration on working memory capacity”

Omar Matoo

Working memory is the ability to temporarily store and recall information. This can be tested by using the Digit Span test, which

involves giving someone a sequence of 3 numbers which they must memorise and then recite 30 seconds after they have been

given said numbers. The aim of our study is to observe the effects of two different exercise intensities (50% HRR and 90% HRR)

and exercise duration on working memory performance and capacity.

Please initial 1. I confirm that I have read and understood the participant information sheet for the above study and have had the opportunity to ask questions

2. I understand that my participation is voluntary and that I am free to withdraw at anytime without giving a reason

3. I understand that all the information I provide will be treated in confidence and only disclosed to people detailed on the Participant Information Sheet

4. I agree to take part in the research project

Name of participant: ____________________ Signature of participant: _________________________ Date: _____________ Name of Researcher:________________________ Signature of researcher: __________________________ Date:___________________________ A CONSENT FORM MUST BE SIGNED BY ALL PARTICIPANTS BEFORE THEY TAKE PART IN THE STUDY AND THE SIGNED FORMS MUST

BE SUBMITTED BY STUDENTS AT THE END OF THEIR PROJECT

Appendix 2 Informed consent form


41

Appendix 3 Digit Span test sheet


42


43

Appendix 4 Standard Departmental Health Screen form


44

11. ACKNOWLEDGEMENTS

First and foremost, I would like to thank Jehovah God for His continued blessings and His

strength. Without Him, my faith and my beliefs, I know I would not be where I am today.

Secondly, I would like to thank my project supervisor, Mike Smith, and Mike Duncan for the

guidance that they have given me across the duration of this project.

Thirdly, I would like to thank Luke McDonald and Nicholas Walker, my co-researchers, for

their help and assistance throughout the entirety of the testing period

Fourthly, I would like to thank the members of Coventry University Team Phoenix male

football club who gave their time and effort to participate in this study.

Lastly, but not least, I would like to thank all my friends (inside and outside of university)

and my family for their encouragement, especially through the past year. Without them and

their support, it would have been near impossible to have seen out the remaining year. I am

forever grateful for all your support.

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