Validity of a pictorial Rate of Perceived Exertion Scale for monitoring ...

int. j. of developmental disabilities, Vol. 59 No. 1, March, 2013, 1–10

Validity of a pictorial Rate of Perceived Exertion Scale for monitoring exercise intensity in young adults with Down syndrome Chih-Chia Chen, Shannon D. R. Ringenbach, Michelle Snow and Lauren M. Hunt Kinesiology Program, Arizona State University, Tempe, AZ, USA

Current studies have indicated that people with Down syndrome (DS) have higher prevalence of cardiovascular disease than their typical peers. The high prevalence of cardiovascular disease is associated with their inactivity. However, it is a challenge to conduct effective exercise programmes because of their poor central executive processing and atypical cerebral specialization which causes a verbal-motor disadvantage. Heart rate (HR) is an index to estimate exercise intensity and Rated of Perceived Exertion (RPE) Scale has been found to have a high correlation between RPE and HR in typical and special populations. Thus, there is a need to develop an effective RPE scale to monitor exercise performance in people with DS in order to improve their health. This study recruited 19 participants with DS and required them to perform a progressive walking protocol on the treadmill for 24 minutes. A pictorial RPE scale was conducted during the duration of walking. Results indicated significant positive relations between HR and RPE in thirteen participants. Even though the results were variable (R2: 0.01–0.93), it revealed that persons with DS were able to perceive and report a subjective estimation of physical exertion, which was reflective of the change in HR. Thus, this modified RPE scale could be applied in training and educational settings to monitor exercise intensity in this population. keywords Down syndrome, RPE, heart rate, treadmill

Introduction Down syndrome (DS) is one of the most common chromosomal diseases associated with intellectual disability. Based on the estimated prevalence of DS ß W. S. Maney & Son Ltd 2013

DOI 10.1179/2047387712Y.0000000005

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in the study of Shin et al. (2009), they estimated that there were 11.8 in 10 000 live births or 83 400 infants with DS during 1999–2003 in the USA. In addition to cognitive impairments, persons with DS also have congenital heart disease, low cardiorespiratory function, low muscle tone, impaired visual and hearing functions, and poor balance ability that impede their participation in physical activities (Block, 1991; Jobling, 1994). Further, these deficits lead to their higher prevalence of an inactive lifestyle (Lotan, 2007) and risk of cardiovascular disease than typical peers (Haveman et al., 2010). Therefore, there is a need to develop a proper exercise programme for this population. However, it is challenging for instructors to implement an effective exercise programme because of their cognitive impairments and physical deficits. In persons with DS, while exercise frequency and duration are relatively easy to monitor; exercise intensity is much more complicated. To our knowledge, the Rate of Perceived Exertion (RPE) Scale has been developed and widely applied to monitor exercise intensity in typical children and adults (Eston et al., 1994). For example, a high positive correlation between RPE and a physiological index that reflects exercise intensity, such as heart rate (HR) (Ueda and Kurokawa, 1995), ventilational threshold (Mahon and Marsh, 1992), and work output (Seliga et al., 1991), has been found. As a result, the higher RPE values represent increases in physiological workload during exercise. As for special populations, there was a similar positive result between RPE and HR in children with cerebral palsy (Birk and Mossing, 1998). Different forms of RPE scales have been used in the exercise programmes for children with asthma (Nystad et al., 1998), cerebral palsy (Schlough et al., 2005) and developmental coordination disorder (Chia et al., 2010), and adults with stroke (Ploughman et al., 2008). However, there is still a debate about the validity of the RPE Scale in persons with intellectual disabilities (ID). Arnhold et al. (1992) used a modified Balk treadmill protocol to determine the predictive ability of Borg’s 6–20 RPE Scale in 10 young adults with ID and found that there was a positive correlation for the relationship between RPE and HR (R250.75, P,0.01). On the contrary, Walleń et al. (2009) omitted their RPE data, collected by the same scale, from analysis because Borg’s 6–20 RPE Scale was too difficult for participants with ID and DS to distinguish exertion among that many numbers during a cycling test. Further, Stanish and Aucoin (2007) conducted the Children’s OMNI 1–10 RPE Scale to examine the usefulness in 14 adults with ID and four adults with DS in a progressive walking protocol on a treadmill. Their statistical results indicated that the significant positive relationship among RPE and HR was only evident in two participants with DS. Based on these studies, it seems that the traditional RPE scale with a wide range of numerical scales and verbal description was too challenging for persons with DS to report their physical exertion accurately. A possible explanation might be because of a deficit in dualtask processing and limited attentional capacities in persons with DS compared with other types of ID and typical peers (Inui et al., 1995; Kittler et al., 2008). In addition, persons with DS also have benefits in visual instruction over verbal instruction because of the atypical cerebral specialization for verbal perception (Elliott et al., 1994; Meegan et al., 2003). Thus, with consideration to the

PICTORIAL RPE SCALE FOR DS

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cognitive, attentioal, and verbal deficits in persons with DS, there is a need to develop a simple pictorial RPE Scale to help them monitor their own exercise intensity. In summary, the purpose of this study is to investigate the effectiveness of a modified pictorial 1–4 RPE Scale to monitor the exercise intensity for people with DS in the present study. We hypothesize that persons with DS are able to perceive their physiological exertion and there is a positive relationship between RPE and HR values in persons with DS.

Methods Participants There were 19 participants in this study. The mean of chronological and mental ages were 21.99¡5.28 and 6.09¡1.78 years, respectively. Height (cm), weight (kg), body mass index (BMI, kg/m2), and body fat (%) are reported in Table 1. The Peabody Picture Vocabulary Test (third edition; PPVT-III) was administrated to interpret the mental age for each participant. PPVT-III is a pictorial assessment of receptive language that is easily administered for a population with verbal deficits. Participants were recruited from a variety of local DS organizations. Interested parents/guardians contacted the researchers via telephone or email and were given a description of the task and eligibility requires for participation. All protocols were approved by the Human Subjects Institutional Review Board of our University.

Protocol Upon arriving, parent/guardians completed our informed consent form and participants signed assent forms. Next, the mental age of the participants was assessed using the Peabody Picture Vocabulary test (third edition, PPVT-III). Participants, whose mental age was lower than 3 years old, were not included in the data collection and analyses because participants, whose cognitive developmental level were lower than 3 years old, have no capabilities to rate their perceived exertion during a physical-demanding task (Groslambert and Mahon, 2005). Thus, it is necessary to ensure that the instructions in the present study can be understood. In addition, participants were not tested if they had medical or physical disabilities, assessed using Physical Activity Readiness Questionnaire TABLE 1 PARTICIPANT CHARACTERISTICS Male (N514)

Female (N55)

Total (N519)

Mental Age (years)

22.99¡5.41 6.06¡1.87

19.18¡4.15 6.18¡1.73

21.99¡5.28 6.09¡1.78

Height (cm)

147.39¡11.85

145.72¡9.64

146.94¡11.08

Weight (kg)

72.71¡23.21

55.84¡12.67

68.27¡21.98

2

33.35¡10.07

25.16¡9.42

31.19¡10.33

Chronological Age (years)

BMI (kg/m )

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(PAR-Q), which would limit their physical involvement. No participant was excluded in this study after pre-screening of PPVT-III and PAR-Q. We modified the Children’s OMNI 1–10 walk/run Scale (Robertson et al., 2000) for rating perceived exertion during walking to a four point scale (Figure 1). The scale has four pictorial representations and corresponding numbers, ranging from 1 to 4. The verbal descriptions were removed. A rating of one represents the statement that ‘The task is easy for me’. This is depicted with a character walking with a smile on the bottom of the hill. A rating of 4 represents the statement that ‘the task is too hard and I want to stop’. This is depicted by a character with their eyes closed and almost falling down on the highest point of the hill. Treadmill (NordicTrack summit 4500, USA) was used to perform a modified progressive walking protocol because an incremental exercise test has been widely applied to assess the validity of different RPE Scales (Eston et al., 2006; Lamb et al., 1999; Robertson et al., 2004). This modified RPE Scale was explained to make sure the understanding of each participant before testing. In addition, a small amount of practice was given to walk on the treadmill at preferred speed for 5 minutes to eliminate the unfamiliarity. In the beginning of the treadmill walking protocol, there were four stages for warm-up period. The treadmill speed was started at 0.5 mph and increased by 0.5 mph each minute until 2.0 mph was reached. Then, the speed were determined by participants between 2.0 and 3.0 mph and held constant while treadmill incline was increased by 2.5% every 4 minutes from 0% to 10%. There were five stages for testing period. During the duration of walking on the treadmill, the participant also wore a heart rate monitor (Polar s801i, USA). HR rate was monitored between 50% and 70% of their predicted maximum HR which was considered as moderate intensity aerobic exercise. Participants can loosely hold the handrails while walking on the treadmill for safety purposes. In addition, participants were verbally encouraged to stay on the treadmill as long as possible. The total time for this intervention is 24 minutes. During the last 15 seconds of each stage, the response of REP scale and the HR were both recorded. Participants were asked to select a number of the picture on the scale in response to their perception of exertion. After the participants pointed a picture on the scale, the tester validated their response by asking probing questions that corresponded with the picture (e.g. ‘Do you feel this task is easy?’ or ‘Do you feel this task is a little difficult now?’). The test was stopped if any of the following conditions were presented; (i) participant’s heart rate reached above 85% of predicted maximum; (ii) participant completed the entire walking protocol; or (iii) participant indicated that they were too tired and/or did not want to continue.

Statistical analysis Because the RPE Scale was based on the assumption that the response to perceived exertion should increase linearly with increasing exercise duration, Spearman’s rank correlation coefficients (rho) were calculated for each participant to examine the individual relationship between RPE and HR.

figure 1 The modified four-point pictorial RPE Scale.


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Regression analysis was also performed on individual data to determine the variance in HR that could be accounted for by changes in RPE. In addition, Alpha was set at P50.05. The SPSS-PC 19.0 statistical package was used for all analyses.

Results Physical characteristics are presented by gender in Table 1. Males were heavier and had higher BMI than females, but there were no gender differences among any other characteristics. Eighteen participants completed all nine stages of the walking protocol. Only participant #10 discontinued walking during the last stage (10% incline) because of the tiredness. Table 2 presents individual relation between HR and RPE. The R2 values between HR and RPE ranged from 0.01 to 0.93. A significant positive relationship existed between HR and RPE for 13 out of 19 participants. No relationship existed for HR and RPE for participants #14 and #15 because they kept reporting the same RPE value during walking. Figures 2 plots mean RPE versus mean HR at each stage during walking. It provides a visual representation of the linearly positive relation between RPE and HR. TABLE 2 SUMMARY OF SPEARMAN’S RANK CORRELATION COEFFICIENT AND REGRESSION ANALYSIS FOR RATED OF PERCEIVED EXERTION PREDICTING HEART RATE (N519) Spearman’s rank correlation coefficient

Regression

B

1 (female)

0.82*

R2 0.67

14.28

3.83

0.82*

2 (female)

20.09

0.01

21.24

5.15

20.90

3 (male)

0.15

0.02

2.16

5.47

0.15

4 (male)

0.44

0.20

5.36

4.11

0.44

5 (male)

0.68*

0.46

8.33

3.42

0.68*

6 (male)

0.97*

0.95

25.36

2.32

0.97*

7 (male)

0.83*

0.69

23.97

6.07

0.83*

8 (male)

0.73*

0.53

5.56

1.97

0.73*

9 (male)

0.52

0.27

3.84

2.38

0.52

10 (male)

0.84*

0.71

5.67

1.36

0.84*

11 (male)

0.82*

0.67

26.67

7.02

0.82*

12 (male)

0.96*

0.93

7.63

0.82

0.96*

13 (female)

0.75*

0.56

14.81

4.93

0.75*

16 (male)

0.96*

0.85

16.25

2.54

0.92*

17 (male)

0.60*

0.36

11.11

5.60

0.60*

18 (male)

0.82*

0.67

10.15

2.72

0.82*

19 (female)

0.58*

0.33

14.56

7.78

0.58*

Participant

rs

SE

Beta

14 (female) 15 (male)

NOTE: *P,0.05.

figure 2 The scatter plot between mean HR and mean RPE values at each stage.


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Discussion This study examined the ability of young adults with DS to rate perceived exertion during a progressive walking test on a treadmill. This study indicates that in general, persons with DS have the ability to perceive physical exertion (e.g. increased HR) and report an accurate subjective estimation during walking. Inconsistent with previous studies in Stanish et al. (2007) and Walleń et al. (2009), most participants with DS in the present study were able to report the increased RPE as the exercise intensity increased because of the significant positive values for Spearman’s rho between HR and RPE values. Therefore, the simplicity of the pictorial RPE Scale may assist participants with DS to overcome their deficits in dual-task processing and limited attention capabilities. This modified pictorial RPE Scale could be used to monitor exercise performance in future training and educational settings in this population. Further, Figures 2 depicts a positive linear relationship for mean RPE versus mean HR values for all participants at each stage during the duration of walking. However, the results of individual regression analyses are variable. The R2 value represents the per cent of variance in HR explained by changes in RPE values. In some participants, almost 100% of the variance in HR could be accounted for by RPE values, whereas in others very little variance was explained. One participant exhibited an inverse relationship (i.e. RPE values decreased as HR increased) and two participants selected the same RPE value throughout the walking test. The possible explanation might be the individual’s level of mental age in this population. Groslambert et al. (2001) compared the correlation between RPE and HR in young children and adults. They found, the R2 level in young children was lower than that observed in adults. This finding demonstrated the effects of age on perceived exertion. Still, the low mental age may influence their abilities to select an RPE value that is accurately reflective of physical exertion. Also, persons with DS have showed significant verbal preservation than typical population (Abbeduto et al., 2006). Thus, the same RPE value was selected can be explained as the performance of their excessive self-repetition behaviour. To avoid this problem, multiple exercise intensities that are not progressively increased have been suggested to avoid recalling previous RPE value in some paediatric studies (Barkley et al., 2009). Furthermore, the limitation of the reliability of RPE Scale should be considered as well. Each participant was only tested once, so future research should investigate the consistency which they rated their exertion by using this modified RPE Scale. Secondly, there were still some participants showed fear during the walking test because of the lack of related experience on a treadmill even after a period of familiarization had been given before testing. Longer practice session or other exercise modules (e.g. stationary cycling) that reduce the psychological factor may be considered in the future studies. In summary, this four-point pictorial RPE Scale is simple and assists persons with DS to eliminate the extra time to process information. In the present study, persons with DS were able to express how tired they were during walking exercise. Therefore, it can be concluded that this modified PRE Scale is a useful tool to monitor exercise performance for adults with DS.


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Acknowledgements Thank you to Sharing Down Syndrome Arizona, Down Syndrome Network, and Tempe Special Olympic programme for helping us with participant recruitment. This project was supported by the Arizona State University Graduate and Professional Student Association’s JumpStart Grant Program.

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Notes on contributors Correspondence to: Chih-Chia (JJ) Chen, Kinesiology Program, Arizona State University, Tempe, AZ, 85287-0701, USA. Email: [email protected]