Master Thesis
Department of Psychology. Faculty of Social- and Behavioral Sciences, University of Amsterdam.
Mind over Muscle – Improving sports
performance with a brief mental training.
University of Amsterdam Written by: D. van der Paard Studentnumber: 10821880
First supervisor: Dr. A. D. van Campen Second supervisor: Drs. G. M. Weltevreden Date: 18August 2016
Table of content
Abstract 3
Introduction 4
Mindfulness 5
Method 8
Participant characteristics & ethical approval 8
Procedure 9
The Mindfulness-based training (MBT) condition 10
The control condition 11
Materials 11
TTE-test 11
Rate of perceived effort (RPE) 11
Heart rate 13 Questionnaires 13 Electronic diary 14 Control variables 14 Statistical analysis 15 Measures 15 Analysis 15 Person correlation 15
Mixed model ANOVA 15
Test of normality 16
Test of equal covariance matrices 16
Test of sphericity 16
Analysis control variables 17
Results 17
Correlation of mindfulness and RPE 17
Effect of MBT on RPE during the TTE-test 18
Effect of MBT on HRV during the TTE-test 19
Effect of RPE on mean heart rate 20
Control variables and manipulation check 22
Discussion 24 Results 24 Explanations 25 Limitations 29 Conclusion 30 Reference list 31
Appendix I: Dutch scripts psycho-education 36
Appendix II: Dutch instructions MBT and control condition 38
Appendix III: standardized RPE instruction 58
Abstract
Purpose: In sports, both physical and mental limitations affect sports performance.
The psychobiological model, proposed by Samuele Marcora, suggests that these limitations are perceived and regulated by the rate of perception of effort (RPE). The RPE is thought to be a conscious sensation of how heavy and strenuous an exercise is perceived. Studies regarding mindfulness revealed that mindfulness positively affect the RPE (e.g. reduce the RPE). Mindfulness has also been positively linked to enhance physical components such as the heart rate variability (HVR). Therefore, this study examined in what way mindfulness relates to RPE and HRV during physical (sport) performance. General research question: Do RPE and HRV improve with a brief Mindfulness-based training (MBT)? Method: Thirty-four participants performed a time to exhaustion (TTE) test on a cycle ergometer. The RPE is recorded every minute on a 15-point Borg-scale. Heart rate is continuously recorded with an electrocardiogram (ECG). The design of this study is a pre- posttest mixed model ANOVA design with between and within subject variables. Participants either received a MBT or control training. Results: Mixed model ANOVAs revealed that the RPE and HRV did not differ between the conditions at the pre- and posttest.
Conclusion: The study found no effect of MBT on RPE and HRV. This study is one
of the first to explore the relationship between mindfulness and RPE. Alternative explanations are discussed and directions for future research implications are considered which provide valuable information for future research.
Introduction
'What you're physically capable of is more determined by your mental strength than your physical capabilities. Your body can go beyond what your physical perceptions of tiredness or fatigue are, your brain will be telling you to stop because you are tired. The mental limitation kicks in before the physical limitations', Andy Scott (43),
ultra-endurance mountain biker and ski mountaineer (Tamarkin, 2014).
The mental limitation Andy Scott describes has been a research topic of interest for several years now in exercise science and Sport Psychology. Sports performance was long thought to be regulated solely by physiological processes (Noakes, 2000; Noakes, 2012; McArdle, 2014). Recently, however, Samuele Marcora introduced a new psychobiological model, in which he hypothesizes that sports performance is regulated by a psychological process, the perception of effort (RPE) (Marcora, 2008). Athletes will continue their exercise until their RPE exceeds the effort that either an individual is willing to take in order to succeed or the task is viewed as impossible at a certain moment in time (Brehm, 1989; Wright, 2008; Smirmaul, Dantas, Nakamura & Pereira, 2013). As such, Marcora's psychobiological model assumes that psychological processes directly influence sports performance. Feedback from physiological processes (heart or lungs) only indirectly (via the RPE) influences sports performance (Lahaye, Hutters & Waanders, 2014). Therefore, the RPE is suggested as a central mechanism which uses information from direct feedback from psychological - and indirect feedback from physiological processes to regulate sports performance. If the RPE is influenced, sports performance will be influenced as well.
Evidence for the importance of RPE is obtained from various studies. In a study by Blanchfield, Hardy, De Morree, Staiano & Marcora (2013), the effects of motivational self-talk on the RPE and sports performance were investigated. Sports performance was measured with a time to exhaustion (TTE) test performed on a cycle ergometer. The participants who received the motivational self-talk intervention enhanced their TTE, whereas no change was found in the control condition. Results also showed that the participants of the motivational self-talk condition reported a reduced RPE during the middle stages of the cycle tasks.
Blanchfield, Hardy & Marcora (2014) likewise found that participants who received another psychological intervention, subliminal priming with happy faces or action words, (‘go’ or ‘energy’), improved their TTE accompanied with a lower RPE. Participants in the control condition were subliminally primed with sad faces or inaction words, (‘stop’ or ‘sleep’) and did not report a lower RPE and enhanced their TTE. The results of the studies mentioned above revealed that psychological interventions which positively influence the RPE (reduce RPE) may positively influence sports performance as well.
Summarizing, psychological interventions seem to influence the RPE and have been purported to also facilitate sports performance. Hence, emphasis should be placed on mental trainings that influence the RPE. One mental training which has been proven to have great impact on psychological variables such as mood, well-being and motivation is mindfulness (Sedlmeier, 2012). The next section further elaborates on of the concept of mindfulness and its potential relationship with physiological performance.
Mindfulness
Mindfulness is a technique that is used to train an athlete’s perception on how
to cope with psychological factors during exercise, such as coping with stress or pain (Baltzell, 2016). The goal of mindfulness is to change the reaction to stress or pain. Instead of focusing on the pain and stress, mindfulness teaches to perceive the pain in an acceptance-based and non-judgmental manner (Birrer, Rothlin, & Morgan, 2012). Thus, if athletes are able to cope with their bodily sensations by perceiving them as less strenuous, then sports performance could be enhanced. The mechanisms of mindfulness have several positive effects on psychological skills of athletes, for example, mindfulness practice improves attention (Chambers, Lo & Allen, 2008), self-regulation and emotion regulation (Carmody, Baer, Lykins & Olendzki, 2009) but also pain management skills (Shapiro, 2006). This effect of mindfulness is often measured with questionnaires. This study will not only measure the effect of mindfulness on psychological variables with questionnaires but also measures the effect of mindfulness on physical variables, which is relatively new in this field of research.
Mindfulness training also has a positive effect on physiological factors such as the heart rate variability (HRV) (Demarzo et al., 2014; Zeidan et al., 2010; Libby, Worhunsky, Pilver & Brewer, 2012 & Nijjar et al., 2014). The HRV, also called interbeat interval, is driven by the autonomic nervous system. A large variation in the HRV is an indication that someone is healthy and able to cope with stress. A small variation of the HRV, for instance during exercise, may imply that someone is stressed out (Börnert & Michael, 2016). Intensive exercise for a duration of six to twelve months may improve the HRV (Levy, Cerqueira, Harp, Johannessen, Abrass, Schwartz, & Stratton, 1998; Nagai, Hamada, Kimura, & Moritani, 2004). Besides exercise, psychological factors, such as stress and anger, may decrease the HRV (Vroemen, 2007). HRV is thus affected by both physiological and psychological processes. Thus, the HRV seems to be a good candidate to measure the effect of stress reduction during sports performance.
Although mindfulness in general has been extensively studied on both physiological and psychological factors, the possible relation between mindfulness skills and RPE is a fruitful novel area of research. If an athlete copes with sensations (such as fatigue, stress or exhaustion) by a mindset of acceptance and non-judgmental, athletes could potentially gain the capacity to enhance their performance. A recent study showed a potential relationship between mindfulness and RPE (Hanneman, 2013). Mindfulness skills were measured with a questionnaire and sports performance with a treadmill exercise test. It was found that mindfulness and RPE negatively correlate with each other. This result implies that participants with higher mindfulness scores reported a lower RPE. A possible explanation for this result is that mindfulness may decrease the RPE by increasing awareness and acceptance of discomfort (differentiating from pain). Thus, mindful athletes may perceive their RPE during exercise as less strenuous than before, which might enhance their performance.
The primary purpose of the present study is to investigate if a brief MBT improves the RPE and HRV during a TTE-test. Mindfulness skills are measured with a questionnaire before the TTE-test. RPE is measured with a rating scale during the TTE-test. The TTE-test was performed on a bicycle ergometer in order to measure sports performance. Furthermore, heart rate was measured throughout the TTE-test.
The hypothesis of this study are: 1) Participants with more mindfulness skills report a lower RPE during the TTE-test (see Figure 1); 2a) The RPE will decrease from pre- to posttest during the TTE-test in both conditions; 2b) The participants who receive the MBT report a significantly lower RPE during the posttest than the pretest during the TTE-test compared to the control condition (see Figure 2 & 3); 3) Furthermore, the hypothesis regarding the HRV are: 3) The participants who receive the MBT show a higher HRV during the posttest than the pretest during the TTE-test compared to the control condition (see Figure 4).
Figure 3: Hypothesis 3.
Figure 1: Hypothesis 1: Participants with more mindfulness
skills report a lower RPE during the TTE-test.
Figure 1: Hypothesis 2b: Participants who receive the
MBT report a significantly lower RPE during the posttest than the pretest during the TTE-test compared to the control condition.
Figure 4: The participants who receive the MBT reveal a
higher HRV during the posttest than the pretest during the TTE-test compared to the control condition.
Figure 2: Hypothesis 2b: Participants who receive the
MBT report a significantly lower RPE during the posttest than the pretest during the TTE-test compared to the control condition. 6 8 10 12 14 16 18 20 RP E Baseline 25% 50% 75% 100% Control condition Pretest Posttest 3,8 4 4,2 4,4 4,6 4,8 5 HR V
MBT condition Control condition
HRV Pretest Posttest 6 8 10 12 14 16 18 20 RP E Baseline 25% 50% 75% 100% MBT condition Pretest Posttest M in d fu ln es s s k ills RPE
Method
Participant characteristics & ethical approvalThis study is conducted at the University of Amsterdam. Initially, the sample size consisted of thirthy-eight individuals (22 females and 16 males; mean ± SD, age: 24,00 ± 2,96). Due to exclusion criteria, the sample size decreased to thirty-four participants (see Table 1: sample characteristics). The sample consisted of students within the region of Amsterdam and Utrecht. The inclusion criteria for this study requires that participants are eighteen years or older and exercise approximately three times a week. Cyclists practitioners were excluded from this study because this may interfere with the TTE-test, which is performed on a cycle ergometer. Furthermore, participants were also excluded from this study if they participated in a mindfulness course or weekly participate in a mindfulness class.
Table 1: Participant characteristics for the control- and MBT condition.
Age Age Control (N=18) Female (N=8) Male (N=10) 23,17 ± 2,60 23,35 ± 2,45 23,00 ± 2,83 MBT condition(N=16) Female (N=12) Male (N=4) 24,50 ± 3,16 24,17 ± 2,95 25,50 ± 4,04
Note: Data are presented as mean and standard deviation. Age is calculated in years.
Participants were questioned regarding their medication use, neurological status and severe injuries to the lower limbs. If students of the University of Amsterdam (UvA) participated in this study, they received five course credit points. A reward of fifty euro was granted among three participants which were chosen randomly. Each participant gave written informed consent prior to the study. All participants received an information brochure prior to the study which explained all procedures related to the study but were naïve of its aims and hypothesis. The experiment and procedures were approved by the Ethic Committee of the Faculty of Developmental Psychology, University of Amsterdam. Additionally, the participants were debriefed by e-mail regarding the aim and hypotheses of this study.
Procedure Intake
During test day 1, (pretest) each participant was informed regarding the purpose of this study with a standardized instruction letter. After reading this, participants had the opportunity to ask questions and signed the informed consent.
Questionnaires
After participants completed the informed consent, the participant filled in questionnaires regarding their demographical data, mindfulness (MAAS), motivation and mood (POMS).
Balance test
Next, participants performed the balance test, which is not further analyzed in this study. Afterwards there was a five-minute break.
TTE-test
Next, the participant performed a TTE-test on a bicycle ergometer. During this TTE-test, the RPE was measured at one-minute time intervals using the 15-point Borg Scale. The heart rate was continuously measured with an electrocardiogram (ECG) throughout the TTE-test. The TTE-test start with a warming up of three minutes. Then power output increased with 30 Watt for every three minutes until the maximum Watt has been reached (330). The participants had to cycle above 80 rates per minute (RPM) during the TTE-test. Exhaustion was reached when the participants cycled under the 80 RPM for five seconds (Blanchfield et al., 2013). No verbal encouragement was provided throughout the test. The experimenter stood next to the participants at all times to measure the variables.
Random allocation
The participants are randomly assigned to either the MBT- or control condition.
Training (two weeks)
After the TTE-test, the participants received standardized instructions from a video fragment (psycho-education). The participants in the MBT-condition received psycho-education regarding mindfulness in sports with the basic principles.
Participants in the control condition viewed a psycho-education where they are educated regarding the effect of training on core stability or injuries for example (Appendix I consists of the scripts of the psycho-education). On the first day of training, the participants received an e-mail with the psycho-education, the audio fragment of day 1 and a motivation questionnaire. Then, every two days, a new training was automatically sent to the participants until the last (sixth) training is completed. The e-mails were automatically sent by using the LOTUS program (specially designed software developed by the UvA)
Posttest
During test day 2 (the posttest), every step from test day 1 was repeated. Visit two ended with a debriefing, and the participants in the control condition received the audio- and video fragments from the MBT, if interested.
Figure 5: Overview procedure.
The Mindfulness-based training (MBT) condition
The MBT was developed in collaboration with mindfulness trainer/psychologist Josine van Vegchel. The goal of this new MBT is to combine a mental training with a physical training. To create this effect, audio fragments that guide the participants during a physical task are created. As the physical task was created to be challenging in a matter of minutes, participants will soon feel like they would want to give up. The audio fragments guided the participants to cope with their
thoughts, feelings and pain during the physical tasks (Appendix II consists of the scripts of the audio fragments).
The control condition
The audio fragments in the control condition consist of information regarding the posture and that the participant has to stay in their exercise position as long as possible. In order to create some variance, there are two different postures in the exercise schedule in both conditions.
Materials TTE-test
A TTE-test has shown to be a valid measure of sports performance (Amann, Hopkins & Marcora, 2007). The TTE-test is used in this study to measure how the RPE and heart rate develops during exercise. The TTE-test start at a power output of 30 Watt and is increased with 30 Watt for every three minutes until the maximum Watt has been reached (330). The participants had to cycle above 80 rates per minute (RPM) during the TTE-test. Exhaustion was reached when the participant cycles under the 80 RPM for five seconds (Blanchfield et al., 2013).
Rate of perceived effort (RPE)
The (RPE) reflects the perception of how strenuous an exercise is perceived. The RPE is measured with the 15-point Borg scale (see Figure 8). It has been proven to be a reliable method because of the standardized protocol provided in order to use the Borg scale (Psycharakis, 2011; Currell & Jeukendrup, 2008). In order to
(Appendix III). During the TTE-test, the experimenter placed the RPE scale next to the participant every minute and was asked to point at the number which describes the RPE at that stage.
In order to allow within-group comparisons regarding hypothesis 2, the TTE-test was standardized at the pre- and postTTE-test for every participant in five time intervals (baseline 0%, 25%, 50%, 75% and 100%). The corresponding value of the RPE was used in further analysis. The first minute of the TTE-test is the baseline which corresponds with 0%. The last full minute is equivalent to 100%. In order to obtain the value corresponding to 50%, the minute at 100% is divided by two. The value at 25% was obtained by dividing the minute at 100% by four. The minute corresponding to 25% is multiplied by three to attain the value at 75% (an example is provided in Table 2).
Table 2: Example regarding how the time intervals and accompanied RPE are gathered.
Baseline RPE RPE 25% RPE 50% RPE 75% RPE 100% Pretest RPE Minutes (final minute 7 1 10 5 15 10 17 14 20 19
= 19). Posttest RPE Minutes (final full minute = 20). 7 1 11 5 14 10 16 15 20 20 Heart rate
In order to measure the HRV, heart rate was measured continuously during
the TTE-test with an electrocardiogram (ECG). ECG is found to be a very reliable method to measure the heart rate (Nunan, Donovan, Jakovljevic, Hodges, Sandercock & Brodie, 2009). Three electrodes were placed on the chest in order to measure heart rate. The heart rate was analyzed with the Vsrrp98 program created by Bert Molenkamp from the technical research support at the UvA. This software computed the mean heart rate per minute and the root mean squares of successive differences (rMSSD) of the interbeat intervals. The HRV is calculated by using the rMSSD, which is necessary for hypothesis 3. Due to noise in the laboratorium, the rMSSD was sometimes inconsistent and revealed extremely high values. In order to extract the extreme high and inconsistent values of the rMSSD from further analysis, a cut off score was calculated. The mean rMSSD was multiplied by 2,5 times the standard deviation. Values which are above the cutoff value are extracted from further analysis.
Questionnaires
Mood is measured by a shortened Dutch version of the Profile of Mood States
(POMS). The POMS is a standardized psychological test to assess five mood states: Anger, tension, fatigue, confusion, depression and vigor (McNair, Lorr & Droppleman, 1971).
These five scales are operationalized in 32 adjectives which are rated on a 5-point Likert scale (ranging from 0 ‘Not at all’ to 4 ‘Very much’) (McNair, Lorr, & Droppleman, 1971; Wal & Mellenbergh, 1990). Examples of adjectives are: ‘sad’ or ‘tired’. The POMS is used in this study to assess in which mood the participants are before they perform the pre- and posttest because mood may influence the sports performance (Blanchfield et al., 2014). The higher the scores on a scale are, the bigger the emotional disturbance is. The Dutch POMS questionnaire is a reliable
with a Cronbach alpha for different scales, varying between .85 and .95 (De Groot, 1992).
Mindfulness is measured in this study for two reasons. It is possible that
participants who received the MBT already have good mindfulness skills, otherwise stated: they have a predisposition to mindfulness.
This may influence the results of the study. The Dutch version of the Mindful Attention Awareness Scale (MAAS) (Brown & Ryan, 2003) questionnaire is used in this study. The MAAS questionnaire consists of 15 items rated on a 6-point Likert scale (ranging from 1 ‘Almost Always’ to 6 ‘Almost Never’). An example item is: ‘I could be experiencing some emotion and not be conscious of it until sometime later’. The total score of the MAAS is calculated. The higher the score on the MAAS scale, the more mindful a participant is. This questionnaire is a reliable and valid tool. Cronbach’s alpha varies between .82-.87 (Schroevers, Nykliček, & Topman, 2008). This questionnaire is also used as a manipulation check to measure if the MBT increases the mindfulness skills of the participants.
Electronic diary
The participants received a questionnaire regarding motivation when they finished the exercise. The questionnaire was incorporated in this research to check the motivation of the participants and whether the participants really performed the exercises. The motivation questionnaire consists of four questions regarding motivation which are rated at a 10-point Likert scale (ranging from 1 ‘Not at all motivated’ to 5 ‘Extremely motivated’). An item (for instance) is: ‘How motivated were you to complete the exercise?’
Control variables
The control questionnaire consists of seven questions which will be answered with ‘yes’ or ‘no’. An example item is: ‘I have consumed alcohol today’. If questions like these are answered with ‘yes’, an additional question is asked to gather more information.
Statistical analysis
MeasuresThe measures in this study consist of the RPE, TTE-test and HRV. The RPE is represented in three ways. First, the RPE is measured in order to investigate how mindfulness skills and RPE are related to each other (hypothesis 1).
Second, it is investigated what the subjective experience of effort (RPE) is during a physical task (TTE-test) at certain standardized percentages of time (hypothesis 2). Third, it is investigated what the value of a physiological measure (heart rate) is at a certain standardized value of RPE (feelings of fatigue, exhaustion) (additional analysis). HRV is measured in order to investigate if the MBT affects physiological processes such as the HRV during a physical task (hypothesis 3).
Analysis
Person correlation
First, the Pearson product correlation coefficient was calculated between the total score of the MAAS questionnaire and the mean RPE at the pre- and posttest for each condition. These correlation coefficients reflect the association between mindfulness skills and the RPE (hypothesis 1).
Mixed model ANOVA
Second, a mixed model ANOVA was used in order to investigate hypothesis
2,3 and additional analysis. The mixed model design consists of two or more
variables, a between subject (condition) and within subject variable (time, RPE and/or HRV). For the mixed model analysis, the same between and within variables are used. The between subject variable is Condition (the MBT- and control condition). The within subject variables are Time and Test. Time has five levels (baseline 0%, 25%, 50%, 75% and 100%). Time is the standardized TTE-test in hypothesis 2 and 3 and
standardized RPE in the additional analysis. Test is the pre- and posttest.
Test of normality
The assumption for normality has been tested with the Shapiro-Wilk test. If the Shapiro-Wilk test was significant, histograms were analyzed and outliers were detected with boxplots (Penders, 2015). The data regarding RPE shows one significant outlier which is excluded from all analyses with RPE as a variable. After this extraction, the Shapiro-Wilk test was still significant for several levels of RPE at the pre- and posttest in both conditions. This result implies that the sample of the RPE data is not normally distributed.
The data regarding the HRV also show that the sample is not normally distributed. No significant outliers or strong skewness were detected from the histograms. For ease of interpretation, the untransformed raw scores were used for the analysis. Furthermore, as the sample size is greater than N >30, the central limit theorem predicts that the sampling distribution will be approximately normally distributed. As ANOVA is robust against the violation of normality of distributions (Penders, 2015), its use is still valid in this case.
Test of equal covariance matrices
Besides normality, it is also important for the analysis that every between subject variable has the same variance and covariance at the dependent variables (Time and Test). The Box's Test of Equality of Covariance Matrices was used in order this test assumption (Penders, 2015). For every analysis, Box's Test of Equality of Covariance Matrices revealed that the conditions have the same variance and covariance on the dependent variables.
Test of sphericity
Since the time factor (TTE-test or RPE) represents an underlying scale (five factors; baseline, 25%, 50%, 75% and 100%), polynomial contrasts are a powerful option to analyze the within subject effects. The contrast analysis seeks out specific trends for the development of RPE across time, instead of comparing the time points in general (which is done with the Test of Within-Subject effects). Within the contrast analysis, the variance of difference scores is not equal across groups. The assumption of sphericity does not account for the contrast analysis and is not controlled for in this study (Penders, 2015).
Analysis control variables
A mixed model ANOVA with between factor condition and test as within factor is also used to analyze if the mindfulness skills, mood and motivation differences between conditions at the pre- and posttest. A one-way ANOVA was also a valid option as analysis but if scores do not differ at the pre- and posttest, the mixed model ANOVA provides insight in the development of the scores (increase or decrease) from the pre- to posttest. Thus, the output of the mixed model ANOVA provides more information than the output of a one-way ANOVA.
Significance was set at .05 (two-tailed) for all analyses. The assumptions are met for most analyses. If not, it is reported in the results section. Due to a lack of comparable parametric designs, the mixed ANOVA is still used to analyze the data.
Results
Correlation of mindfulness and RPEResults of the correlation matrix reveal that in the control condition, there is no relationship between the score on the MAAS questionnaire at the pretest and the mean RPE at the pretest, r = -.090, p = .732. The scores of the MAAS questionnaire at the posttest and the mean RPE at the post test is similar to the previously mentioned results, r = -.096, p = .714. In the experimental condition results also show no relationship between the scores of the MAAS questionnaire at the pretest and the mean RPE at the pretest, r = -.454, p = .077. The same goes for the scores of the MAAS questionnaire at the posttest and the mean RPE at the post test, r = -.362, p = .168. However, the correlations coefficients are negative which was expected. A negative correlation would have indicated that the higher the scores on the MAAS questionnaire were, the lower the mean RPE on the pre and posttest in both conditions. In the overall correlation matrix, it is shown that the scores on the MAAS questionnaire negatively correlates with the RPE at the post-test (r = -.283, p = .111). One might wonder if mindfulness skills predict the RPE at the posttest. A linear regression was calculated to predict the RPE at the posttest on mindfulness skills. A non-significant equation was found F(1, 32) = 2,699, p = .11, with a R^2 of .080 In
other words, 8% of the variability of the MAAS scores can be accounted for by RPE score at the post-test.
Effect of MBT on RPE during the TTE-test
A mixed model ANOVA is used with Condition as the between subject variable and Time (TTE-test) and Test as within subject variables to test if the RPE differs between conditions at the pre- and posttest. A significant main effect of Time was found, F(1,31) = 2149,32, p = <.001, partial eta squared = .986. This result implies that the RPE increased over time. There was also a significant main effect of Test, F(1,31) = 7,778, p = .009, partial eta squared = .201. This result implies that the increase of RPE differs between the pre- and posttest.
There is a significant two way interaction between Time and Test, F(1,31) = 6,866, p = .013, partial eta squared = .181. This result implies that the increase of RPE during the TTE-test differs per pre- and posttest. This difference is shown in Figure 9: the RPE starts at a lower value at the pretest than the posttest, although the values converge over time. This result is agreement with the expectation of this study which expected that the RPE is lower at the posttest in both conditions. Because of the interaction between Time and Test, simple effects of Time were investigated per Test. The follow up analysis showed that the RPE develops linearly in time at the pre-, F(1, 31) = 1617,697, p = <.001, and posttest, F(1, 31) = 1699,368, p = <.001.
An
interaction effect was expected in which the participants, who receive the MBT,
Figure 9: The Time (TTE-test) x Test (pre- vs. posttest) interaction. The increase of RPE during the TTE-test differs per
pre- and posttest. The error bars are the standard errors. 6 8 10 12 14 16 18 20 RP E Baseline 25% 50% 75% 100% TTE-test
Test x Time interaction
Pretest Posttest
report a significantly lower RPE during the posttest than the pretest compared to the control condition. Results reveal that there is no significant interaction of Condition x Time x Test, F(1, 31) = 1,270, p = .268, partial eta squared = .039. This result implies that, contrary to the hypothesis, the decrease of RPE during the TTE-test did not differ between the pre- and posttest in both conditions (Figure 10 and 11).
Effect of MBT on HRV during the TTE-test
A mixed model ANOVA is used with Condition as between subject variable and Test as within subject variable to test how the HRV differs between conditions at the pre- and posttest. The results reveal no main effect of Test on HRV, F(1, 29) = 1,869, p = .182, partial eta squared = .061. This result implies that the overall HRV did not differ at the pre- and posttest. Contrary to
3 3,5 4 4,5 5 5,5 rMSSD
MBT condition Control condition The effect of MBT on HRV Pretest Posttest 6 8 10 12 14 16 18 20 RP E Baseline 25% 50% 75% 100% TTE-test MBT condition Pretest Posttest 6 8 10 12 14 16 18 20 RP E Baseline 25% 50% 75% 100% TTE-test Control condition Pretest Posttest
Figure 10: RPE at standardized values of the TTE-test for
the MBT condition per the pre- and posttest. The error bars are the standard errors.
Figure 11: RPE at standardized values of the TTE-test
for the control condition per the pre- and posttest. The error bars are the standard errors.
Test, F(1, 29) = 1.257, p = .271, partial eta squared = .042. This result implies that between the conditions, the increase of HRV from pre- to posttest did not differ (see
Figure 12).
Effect of RPE on mean heart rate
An additional analysis was performed in order to investigate what the value of a physiological measure (heart rate) is at a certain standardized interval of RPE. The RPE is standardized the same way as the TTE-test (see Table 2). In order to interpret the results more easily, the corresponding mean heart rate of the standardized RPE is used instead of the HRV.
A mixed model ANOVA is used with Condition as between subject variable and Time (RPE) and Test as within subject variables. There is a significant main effect of Time, F(1,23) = 399,390, p = <.001, partial eta squared = .946. This result implies that the mean heart rate increases with higher levels of RPE. Results also reveal a significant main effect of Test, F(1,23) = 22,365, p = <.001, partial eta squared = .493. This result implies that the mean heart rate differs between the pre- and posttest. Results also reveal a significant interaction of Condition x Time (RPE) x Test, F(1, 23) = 8,952, p = .007, partial eta squared = .280. This result implies that between both conditions, the increase of the mean heart rate with RPE differs between
Figure 12: The HRV during the TTE-test for the MBT- and control condition at the pre-
the pre- and posttest. Because of the significant interaction effect, the file is split per condition in order to see the simple effects.
Simple effects regarding the effects of Test and Time on heart rate, for the
MBT condition (Figure 13), revealed that there was a significant main effect of Time
(RPE) on heart rate, F(1, 11) = 169,807, p = <.001, partial eta squared = .939. Implying that the mean heart rate increases with higher levels of RPE. Results also revealed a significant main effect of Test, F(1, 11) = 9,278, p = .022, partial eta squared = .458. This result implies that the mean heart rate differs between the pre- and posttest. There is no significant interaction between Time and Test, F(1, 11) = 2,583, p = .272, partial eta squared = .190. This result implies that within the MBT
condition, the increase of the mean heart rate with higher levels of RPE did not differ
between the pre- and posttest. Simple effects regarding the effect of Test and Time on the mean heart rate for the control condition (Figure 14) revealed that there was a significant main effect of Time (RPE) on the mean heart rate, F(1, 12) = 239,553, p = <.001, partial eta squared = .952. Implying that the mean heart rate increases with higher levels of RPE during the TTE-test. There was also a significant main effect of Test, F(1, 12) = 13,473, p = <.006, partial eta squared = .529.
This result implies that the mean heart rate differs between the pre- and posttest, F(1, 12) = 13,473, p = .006, partial eta squared =.529.
80 100 120 140 160 180 M ean h ear t r at e Baseline 25% 50% 75% 100% RPE Control condition Pretest Posttest 80 100 120 140 160 180 M ean h ear t at e Baseline 25% 50% 75% 100% RPE MBT condition Pretest Posttest
Figure 13: Mean heart rate at standardized values of RPE
during TTE-test for the MBT condition per pre- and posttest. The error bars are the standard errors.
Figure 14: Mean heart rate at standardized values of
RPE during TTE-test for the control condition per pre- and posttest. The error bars are the standard errors.
Finally, there is a significant interaction effect in the control condition between Time x Test, F(1, 12) = 7,524, p = .036, partial eta squared = .385. This result implies that, within the control condition, the increase of the mean heart rate with RPE differs between the pre- and posttest. This difference can be seen in Figure
12, the mean heart rate is lower at the posttest than the pretest at every interval of the
RPE. Because of this interaction, the data is further split in simple effects in order to analyze per Test the Time effect. The analysis shows that the mean heart rate at the pre-, F(1, 12) = 304,253, p = <.001, and posttest, F(1, 14) = 168,078, p = <.001, develop linearly in time in the control condition.
Control variables and manipulation check
A mixed model ANOVA with Condition as between factor and Test as within factor is used to analyze if the mindfulness skills differ between conditions at the pre- and posttest. A significant main effect of Test was found, F(1, 32) = 6,148, p = .019, in which the MAAS scores significantly decreased from the pre- to the posttest in both conditions. This result will be further elaborated on in the discussion. Results reveal no significant interaction between condition x test, F(1, 32) = ,457, p = .504. This result implies that the decrease in the MAAS scores from the pre- to posttest, did
not significantly differ between conditions (Figure 15). 46 51 56 61 T o tal s co res MA A S
MBT condition Control condition Scores MAAS questionnaire
Pretest Posttest
Figure 15: The total scores of the MAAS questionnaire per condition at the pre- and posttest. The error bars are the
A mixed model ANOVA with Condition as between subject variable and Test as within subject variable is used to analyze if the motivation differs between conditions at the pre- and posttest. Scores on the motivation questionnaire were not normally distributed in the control condition at both the pre and posttest. Nevertheless, the sample size is greater than N >30, therefore the central limit theorem predicts that the sampling distribution will be approximately normal. Thus, the ANOVA is robust against the violation of normality of distributions (Penders, 2015). Results revealed no main effect of Test on motivation, F(1, 31) = 2,581, p = .118. This result implies that motivation scores does not differ from pre- to posttest. Results also revealed no significant interaction effect, F(1, 31) = ,126, p = .725. This result implies that, within both conditions, the motivation did not significantly differ between the pre- and posttest. This will be further elaborated on in the limitation section of this paper. Finally, the mood of the participants is measured. A mixed model ANOVA with Condition as between subject variable and Test as within subject variable is used to analyze if mood differs between conditions at the pre- and posttest. The Box's Test of Equality of Covariance Matrices revealed a significant value (p = .017) for the POMS questionnaire, but the condition sizes were near-equal in size and therefore the ANOVA is robust against unequal covariance matrices.
Results revealed no main effect of Test on mood, F(1, 32) = 1,638, p = .210. This result implies that mood does not differ from pre- to posttest. Results also revealed no significant interaction effect, F(1, 32) = 1,312, p = .260. This result implies that, within both conditions, the mood did not significantly differ between the pre- and posttest. Concluding, mindfulness, motivation and mood were not statistically significant different between conditions at the pre-and posttest.
Table 3: Mean and standard deviation (SD) of the MAAS, POMS and motivation questionnaires.
MAAS POMS Motivation
Pretest Posttest Pretest Posttest Pretest Posttest
Discussion
This research is based on the framework of the psychobiological model which states that sports performance is regulated by the RPE (Marcora, 2008). This study investigated whether a brief MBT affects the RPE and HRV during sports performance. This section further elaborates on the results of this study. Next, possible explanations are provided. Then possible limitations of this study are mentioned. Finally, the conclusion of this study is provided.
Results
First, results revealed that there is no relationship between the scores on the MAAS questionnaire and the RPE in both conditions. However, the scores of the MAAS questionnaire at the pretest and mean RPE behave, as expected, in a negative manner. Results revealed that 8% of the variability of the MAAS scores can be accounted for by RPE score at the post-test. Second, results regarding the effect of MBT on the RPE revealed that the RPE did differ per pre- and posttest between the conditions. The RPE starts at a lower value at the pretest than the posttest, although the values converge over time. Results revealed that the decrease in RPE did not significantly differ between conditions at the pre- and posttest in the MBT-condition. Third, results regarding the effect of MBT on HRV reveal that the HRV did not differ between groups at the pre- and posttest. Fourth, additional analysis regarding the effect of RPE on heart rate reveals that the heart rate differs between the conditions. Results revealed that within the control condition, the heart rate is lower at every standardized RPE interval, during the TTE-test, at the posttest compared to the pretest. This result was not found in the MBT condition. Finally, results regarding control variables revealed that mindfulness, motivation and mood were not statistically significant different between conditions at the pre-and posttest. Some of the expected condition
MBI-condition
56,75 (7,12) 54,13 (6,63) 20,38 (2,59) 20,56 (9,80) 5,94 (1,95) 6,31 (2,12)
results are not confirmed in this study. In the next section part, possible explanations will be further discussed.
Explanations
There are possible explanations regarding why the expected results are not found in this study: 1) The sample size of this study may be too small; 2) Certain aspects of the MBT may be limited in learning mindfulness skills; 3) The mechanism of the RPE could be measured differently; 4) The combination of mindfulness during exercise may not be ideal to measure the effect of mindfulness on HRV; 5) The instructions of the audio fragments in the control condition might induce an external focused attention; 6) The participants knew that they would perform the TTE-test again at the posttest. This might have negatively influenced the ratings of the participants on the MAAS questionnaire. Next, the alternative explanations are discussed more extensively.
The sample size of this study might be too small
First, contrary to the expectations, there was no relationship between the scores on the MAAS questionnaire and the RPE in both conditions. A previous study of Hanneman (2013) did find a significant negative relationship between mindfulness skills and RPE with a sample size of ninety students. This study consists of a smaller sample size (thirty-four) which may explain the non-significant relationship. The scores behaved as expected, in a negative manner.
A possible explanation for this result is that mindfulness skills may decrease the RPE by increasing awareness and acceptance of discomfort (differentiating from pain) (Birrer, Rothlin, & Morgan, 2012). Thus, mindful athletes may perceive their RPE during exercise as less strenuous.
Certain aspects of the MBT might be limited in learning mindfulness skills
Second, results revealed that there is no effect of MBT on RPE during the TTE-test. A possible explanation could be found in the effectiveness of the MBT. It could be that certain aspects of the MBT training are limited in learning mindfulness skills. Other models such as the Mindful Sport Performance Enhancement (MSPE) and Mindfulness-Acceptance-Commitment (MAC) approach are found to be effective in enhancing mindfulness skills (De Petrillio, Kaufmanet, Glass & Arnkoff, 2009;
Thomposon, Kaufman, De Petrillo, Glass & Arnkoff, 2011). These models are more intensive in duration of sessions (five hours per session) and frequency (twelve or more) in sessions (Baltzell, Ahktar 2014). However, the MBT is specifically designed to be brief in duration and frequency in order to create a training in which mindfulness is learned within a few weeks with short sessions. This is to allow the training to fit in the training schedule for athletes. Therefore, this study developed a mindfulness training program which consists of six sessions of ten minutes across two weeks. Another brief mindfulness training is the Meditation Mindfulness Meditiation for Sports (MMTS), which consists of twelve sessions of thirty minutes. MMTS has been shown to be effective in producing higher mindfulness scores (Baltzell & Ahtkar, 2014). Other studies who developed brief mindfulness training used a three or five-day training session (twenty minutes) of mindfulness meditation intervention. Results reveal that training significantly reduced the pain ratings (Zeiden, Gordon, Merchant & Goolkasian, 2010) but also improves attention, lower anxiety, higher vigor on the POMS scale and less fatigue (Tang et al., 2012). In sum, these studies show that brief mindfulness interventions do work.
Another explanation focuses on personal guidance throughout the MBT training. Studies regarding mindfulness show that a certain level of expertise or practice is needed to learn mindfulness skills (such as controlling attention) (Brefczynski-Lewis, Lutz, Schaefer, Levinson & Davidson, 2007). Learning mindfulness acquires practice and people learn by their experience which they can evaluate with or during their mindfulness sessions (Gupta, Singh, Bhatt & Gupta, 2015). The study of Blanchfield et al. (2013) provided workshops regarding self-talk in which the participant got personalized with and practiced the use of motivational self-talk. The participants in this study only received guidance via the audio fragments. With the MBT (and control training) there was no room for reflection which is very important in order to learn mindfulness. So it could be that the participants did not actively and consciously learned the mindfulness skills.
The mechanism of the RPE could be measured differently
Third, another alternative explanation could be given from the use of the Borg-scale. The Borg scale is used to ask the participants to rate their perception of effort and thus, they need to reflect how they are feeling at that moment. This reflection also
implies that the participants will focus their attention towards their physical feelings such as pain or fatigue. Therefore, the participant becomes conscious about this which may negatively influence the RPE.
Marcora’s psychobiobiological model suggests that sports performance is regulated by the RPE. The mechanism of the RPE is measured with the Borg-scale at several time intervals during exercise. A popular theory in neuroscience is predictive coding which could provide a different view of how the mechanism of RPE works and how this could be manipulated and tested. Predictive coding states that the brain continuously generates a prediction (expectation) based on knowledge, experience and memories. This expectation then guides the perception (Brown & Brüne, 2012). In other words, the expectation which someone has before exercise will influences the RPE and sports performance. If someone learns that during exercise, things will get tough but this moment will go away, this may positively influence the expectations of the exercise. This could then positively affect the perception during exercise. According to the theory of predictive coding, it might be better to manipulate the mechanism of the RPE regarding the expectation which someone has before the exercise start. Then, the RPE could also be tested before the exercise start because this may be leading for the perception during exercise and sports performance. This study focused on manipulating the RPE during exercise, when someone is exhausted which is tested during exercise. The theory of predictive coding provides a possible alternative explanation regarding why the MBT may not have worked.
The theory of predictive coding does not contradict the theory of Marcora’s psychobiological model but provides another point of view regarding the mechanism of the RPE.
The combination of mindfulness during exercise is not ideal to measure the effect of mindfulness on HRV
Fourth, results reveal no effect of MBT on HRV. Research regarding the effect of mindfulness on HRV focused on mindfulness tasks which involves slow breathing exercise at rest (Krygier et al., 2013) This study used mindfulness tasks during exercise. Difference between these studies can be explained by the influence of
produces higher amplitudes of HRV than faster respiration rates (Song & Lehrer, 2003) Therefore, the circumstances in which mindfulness is applied may influence the effect on HRV and explain the results of this study. HRV is also found to improve over a longer period of time (six to twelve months) of intensive exercise (Levy, Cerqueira, Harp, Johannessen, Abrass, Schwartz, & Stratton, 1998; Nagai, Hamada, Kimura, & Moritani, 2004). In this study, the two weeks of exercise could be too short to affect the HRV.
The instructions of the audio fragments in the control condition might induce an external focused attention
Fifth, results regarding the additional analysis implies that the training in the control condition is more effective on heart rate than the MBT. Instead of looking at the time, frequency and guidance throughout the MBT, the content of the MBT may also explain this result. The instructions of the audio fragments in the MBT condition are provided from an internal perspective, focusing on internal bodily processes: ‘Send your attention to your respiration in order to let go of your thoughts’, ‘Focus your attention to the movement of your stomach, in and out’. The instructions of the audio fragments in the control condition are also provided from an internal perspective but only focuses on the position of the human body: ‘Make sure that you stay in the right position’, ‘Check if your knees still stand in a corner of 90 degrees’. It could be that the instructions provided in the control condition induced a more external attentional focus (which created an image regarding how the exercise should be done), whereas instructions in the MBT condition induced an internal attentional focus. Research regarding attentional focus reveals that instructions who induce an external attentional focus are more effective in learning motor skills. This is because an external attentional focus facilitates automaticity in movement whereas internal attentional focus may disrupt the automaticity of a movement (Wulf & Lewthwaite, 2010).
In this case, it could be that the instructions in the control condition removed the focus away from the internal processes such as pain and fatigue, which enhanced the physiological response to these processes during exercise.
might have negatively influenced the ratings of the participants on the MAAS questionnaire
Finally, results regarding control variables revealed that there is no difference between scores on the MAAS, motivation and POMS questionnaires. Results regarding the motivation and POMS questionnaire are used as control variables and are not further discussed in this section. The MAAS questionnaire was used as a control variable and manipulation check. Results regarding the MAAS questionnaire reveal a decrease from pre- to posttest in both conditions. The MAAS questionnaire was conducted before the TTE-test started at the pre- and posttest. The participants knew that they would perform the TTE-test again at the posttest. This might have negatively influenced the ratings of the participants on the MAAS questionnaire.
Limitations
Potentially limiting aspects of the study should also be acknowledged. First, the participant’s characteristics are a possible limitation of this study. The sample size consisted of students who exercise several times a week on a recreational level, not athletes who exercise daily in order to increase their sports performance. Also, the participants from the UvA could earn participation points which could affect their motivation. If the MBT training was provided to athletes, a possible effect of training could have been found because athletes may be more motivated to use the MBT to increase their sports performance. Following the first limitation, a possible limitation concerns how motivation is measured in this study. Motivation is measured with a questionnaire. Results revealed no significant differences regarding motivation between conditions at the pre- and posttest.
Nevertheless, a disadvantage of questionnaires in general is that participants may answer from a socially desirable perspective. Consequently, the results may not provide a realistic reflection of the motivation between conditions during the training period. Third, there is no manipulation check regarding if participants used one or more mental strategies during the TTE-test. It could be that participants used a mental strategy to cope with the pain or stress during the TTE-test. Another possibility is that the participants did not use the strategies that they learned during the training. Consequently, a possible transfer effect is not measured either in this study. Lastly,
9:00 A.M. to 7:00 P.M, which may have affected RPE. However, this study is an exploratory study which is based on very scarce research regarding the effect of mindfulness on RPE. Therefore, this information is also interesting to include in possible new research studies.
In light of the findings of this study, future research should explore the relationship between mindfulness and RPE. This field of research is very scarce and this new area of research is very limited in theoretical backgrounds and research results. It is interesting to investigate possible mediators/moderators which influence this relationship. Next, further research could develop an adjusted MBT which is still brief but more intense (for instance ten days in a row with sessions of twenty minutes) and provides personal guidance. This new MBT could be tested again and it could be analyzed if it positively affects mindfulness skills and thus, RPE. Additionally, further studies should include a larger sample. Also, it would be interesting to test the MBT with athletes. Finally, it would be interesting to further investigate the neural mechanisms/structures of the RPE during sports performance in order to obtain more knowledge regarding the RPE and how it could positively be influenced during exercise. One suggestion is to further explore the regional brain activity in order to better understand the neural process responsible for the development of the RPE during exercise. How multiple sensory signals from both psychological and physiological processes are prioritized and processed during exercise for the development of the RPE.
Conclusion
In summary, although the theoretical background of this study seems plausible, the study did not provide evidence that the MBT positively affects RPE and heart rate during sports performance. Hence, the theory of the psychobiological model is not supported. Alternative explanations are presented regarding the sample characteristics and content of the MBT which provide valuable information for future research. For instance, the intensity or frequency of the MBT.
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Appendix I: Dutch scripts psycho-education
Script psycho-educatie MBIBij mindfulness, denken mensen vaak aan iets zweverigs of iets waardoor je mooiere gedachten kan hebben. Maar mindfulness kan je juist goed gebruiken voor het verbeteren van je sportprestatie. Mindfulness maakt je volledig bewust van je lichaam in het hier en nu en hoe je dit op een positieve manier kan gebruiken tijdens je training. Wat betekent dit nou, stel je bent aan het sporten en op een gegeven moment ben je met je aandacht alleen maar gefocust op hoe moe je bent, hoe zwaar je armen zijn en de verzuring in je benen. Door de aandacht hier naar toe te brengen worden de ervaringen alleen maar intenser en voelt het sporten steeds zwaarder…. Mindfulness biedt je een handvat om hier anders mee om te gaan. Met mindfulness leer je dat lichamelijke signalen tijdens het sporten zoals pijn en verzuring, in eerste instantie signalen zijn van het brein die aangeven dat je vermoeid begint te raken. We weten echter uit onderzoek dat je meestal meer kan dan je denkt... Met mindfulness leer je de lichamelijke signalen anders interpreteren. Dit kun je trainen door te accepteren dat dit signalen zijn die bij het sporten horen en door je aandacht te verleggen. Je kunt je aandacht bijvoorbeeld richten op je ademhaling of een bepaald extern punt... Het verleggen van je aandacht kan je zien als het trainen van een spier. Na een bezoek aan de sportschool zul je niet ineens gespierd zijn. Om gespierd te worden moet je herhaaldelijk trainen. Hoe vaker je het traint hoe gespierder en vaardiger je wordt. De komende twee weken zul je thuis aan de slag gaan met het trainen hiervan. Tijdens de thuis- trainingssessies neem je afwisselend een van de twee volgende houdingen aan. Houding 1: (wordt voorgedaan en ondertussen hoor je)
Je armen strek je recht vooruit zodat je een hoek van 90 graden maakt met je buik. Je handpalmen wijzen omlaag en je vingers naar voren. Zet je voeten op heupbreedte stevig op de grond. Je buigt je knieën alsof je op een stoel gaat zitten. Je kan ook echt op een stoel gaan zitten en dan tien centimeter er boven gaan hangen zodat je zeker weer dat je goed staat.
Houding 2: (wordt voorgedaan en ondertussen hoor je) Zet je voeten wederom op heupbreedte en stevig op de grond. Je armen strek je langs je oren naar boven en je vingers wijzen naar het plafond. Ga nu op de bal van je voet
