Balance and upright postural control are fundamental components of movement 1 that involve both the ability to recover from instability (as in a response to an external perturbation) and the ability to anticipate and move in ways to avoid instability (as in a response to an internal perturbation, or self-initiated movement). 2 Computerized force platforms provide the gold standard of measurement of balance;3–6 however, this technology is not widely available to community-based clinicians. For both clinical and population-based research purposes, a measure of “functional” balance feasible to administer in the community is required for children, including those with physical disabilities. The most common childhood disability seen by pediatric physical therapists is cerebral palsy, 7 and is the condition of interest in the research described here. The broad purpose of this line of inquiry is to identify a valid and reliable measure of balance and postural control to be used with children, especially those with cerebral palsy, in a community setting.
Cerebral palsy is the sensory and neuromuscular deficit caused by a nonprogressive brain defect or lesion that occurs during the prenatal, intrapartum, perinatal, or early postnatal periods. 8 Children with cerebral palsy are an extremely heterogeneous group, varying considerably in movement abilities. Children who are mildly involved are able to run and jump, albeit awkwardly, whereas children who are severely involved have limited antigravity postural control and voluntary movement control. 9 Accordingly, a desirable measure should include aspects of balance and postural control in both sitting and standing positions to accommodate children with varying degrees of involvement. In keeping with the “functional” nature of the desired instrument, a measure of response to internal perturbation (ie, self-initiated movement) rather than external perturbation, is preferred. And, although adults are known to rely on visual, somatosensory, and vestibular information to maintain balance and postural control, 2 young children rely most heavily on vision;5,10,11 therefore, a measure with vision unobstructed is optimal. A review of the literature suggested that the Functional Reach Test 12 might be a tool to modify for this population.
The Functional Reach Test 12 was initially developed for use in adult populations. It measures the distance (using a yardstick at the level of the acromion) that an individual is able to reach forward from a starting standing position with a fixed base of support without loss of balance. This measure was determined to be a reasonable approximation of a force platform measure of the foot center of pressure excursion (a laboratory-based gold standard), reliable, and feasible to administer in a clinical setting with adults. 12
The Functional Reach Test has been reported to provide reliable measurements when used in children–both developing typically 13 and with neurological diagnoses. 14 However, it has only been done in the standing position with children, 13,14 and requires participants to be able to stand barefoot in a static position for at least two minutes before testing. 14 This level of ability is only attainable by a small proportion of children with cerebral palsy. 9 A review of the related literature suggested possibly incorporating testing in the sitting position as well as standing as done for persons with spinal cord injuries 15 and side reaching in addition to forward reaching as suggested by Brauer, Burns and Galley 16 in both sitting and standing.
With this literature as a background, the primary author met with three experienced pediatric physical therapists to reach an agreement about the content and protocol for a simple and time-efficient discriminative clinical tool to measure balance in children with cerebral palsy. The score sheet and testing protocol resulting from this consensus exercise that were used in this study are contained in Appendices A and B. The primary objectives of this study were to examine the concurrent validity, construct validity, and reliability of the Pediatric Reach Test (PRT).
Approval was received from the Review Board for Health Sciences Research Involving Human Subjects at the University of Western Ontario before participant recruitment. The concurrent validity testing and a portion of the construct validity testing were done on a sample of children developing typically. The other portion of the construct validity testing, and intrarater and interrater reliability testing were conducted on a sample of children with cerebral palsy.
Twenty children developing typically, aged two to 12 years of age, were targeted for recruitment by contacting parents who were faculty or staff in the Faculty of Health Sciences at The University of Western Ontario. Twenty-two children were recruited to this phase, although two had incomplete data and one child aged two years three months was not cooperative during testing. Data are available from 19 children developing typically (eight boys and 11 girls). These children averaged 8.1 years of age (SD = 2.8), with a range of three to 12.5 years.
Ten children with cerebral palsy were recruited from the Cochrane-Temiskaming Children’s Treatment Centre and they were classified according to their Gross Motor Function Classification System (GMFCS) level. 9 The GMFCS is a reliable and valid system to classify children with cerebral palsy aged two to 12 years based on their age-specific functional abilities from I (child is able to walk and run, but has limitations in more advanced gross motor skills) through V (child has limited voluntary movement). Children unable to follow instructions, such as “reach forward as far as you can,” were excluded from this phase of the study, as were children with GMFCS level V. The rationale for the last exclusion criterion was that these children are so severely involved that they could not complete any of the items on the test. Seven boys and three girls averaging 8.2 years of age (SD = 3.6), with a range of 2.6 to 14.1 years were recruited. Five children had hemiplegia, two children had diplegia, and three children had quadriplegia. Nine children had spastic involvement; one had hypotonic cerebral palsy. Six participants were classified as GMFCS level I, three were level III, and one was level IV.
Instruments and Data Collection Procedures
The standing dimension of the PRT was administered first to the children developing typically by a consistent, trained physical therapy student rater, using the scoring sheet (Appendix A) and the protocol in Appendix B, as illustrated in Figure 1. To be as similar to the laboratory tests as possible, children were tested without socks and shoes, and they were required not to lift their feet from a piece of paper taped to the floor with their foot tracings.
Next, each study participant in the sample of children developing typically was assessed using tests of standing balance performed on a force platform (model OR6-6, AMTI, Watertown, Mass) mounted flush with a surrounding walkway and using protocols similar to those previously used with adults in the Postural Control Laboratory. 17,18 Standing tests of the limits of stability in the anteroposterior and mediolateral directions were assessed. Children stood on the force platform with their arms held at their sides and their feet at a distance apart equal to the foot tracings provided during the PRT. The distal tips of their medial malleoli were aligned with the transverse axis of the platform. Children were instructed to lean forward, moving at their ankles only, as far as possible without lifting their heels off the ground, and to maintain that position for three seconds. Once this position was established, the tester then instructed the children to lean backwards as far as possible without lifting their toes off the ground, and to maintain that position for three seconds. The children then repeated these tests by leaning to the left and then to the right (Fig. 2).
A measure of steadiness during quiet stance using the force platform was subsequently assessed. For this test, children stood on the force platform in the same position previously described and were asked to stand as still as possible for a period of 30 seconds. For all tests (anteroposterior limits of stability, mediolateral limits of stability, and steadiness during quiet standing) children completed one practice trial, followed by three trials of the test. During all laboratory tests, children were continuously reminded of the instructions and were provided verbal feedback regarding their performance. For example, children were reminded to move only at their ankles and to keep their bodies straight “like a Popsicle stick” for the limits of stability tests. If the instructions were not followed, the trial was excluded and repeated.
In a final phase of the study, two trained physical therapy student raters each independently assessed each of the 10 children with cerebral palsy on one occasion (time one: interrater reliability) using the PRT. Both physical therapy students reassessed all 10 of these children one to two weeks later (time 2: for test-retest reliability and a second estimate of interrater reliability).
Before data analysis for the validity and reliability objectives, data from the difference measurements of items in the PRT were summed to obtain standing section scores for the children developing typically and sitting and standing section scores, as well as a total score (in centimeters) for the children with cerebral palsy. The BioSoft Data-Acquisition and Analysis Software (BioSoft version 1.0, AMTI, Watertown, Mass) was used to obtain force platform output at a rate of 50 Hz, and to provide summary statistics for the center of pressure. The limits of stability were quantified as the maximum excursions of the center of pressure (in centimeters) in the anteroposterior direction and in the mediolateral direction and were summarized as the mean of three trials. Greater excursions of the center of pressure during the reach represented greater balancing abilities. Steadiness during quiet standing was quantified as the total length of the path of the center of pressure (in centimeters) throughout the 30-second period, also calculated as the mean of three trials. Greater lengths of the path of the center of pressure during quite standing represented poorer balancing abilities.
Concurrent validity between the standing section of the PRT (forward reach, combined right and left reach, and combined forward, right, and left reaches) and force platform indicators of standing balance (anteroposterior limits of stability, mediolateral limits of stability, and sum of the anteroposterior and mediolateral limits of stability) was analysed using the Pearson’s correlation coefficient. Construct validity was examined through Pearson’s correlation coefficients between the standing section of the PRT and the measure of steadiness during standing and age of the children developing typically. Construct validity with children with cerebral palsy was analyzed by examining the strength of the relationship between the GMFCS and the total PRT score. The intraclass correlation coefficient (ICC, 2,1 Shrout and Fleiss) 19 was used to estimate interrater and test-retest reliability using data collected with the children with cerebral palsy. For all of these analyses, a p value of 0.05 was used for significance testing.
Measurements from 19 children provided a power value of 0.95 to detect a Pearson’s correlation coefficient of >0.70 at a two-tailed alpha level of 0.05 (see Table 3.3.5 in Cohen). 20 For the reliability testing on the sample of children with cerebral palsy, a sample of 10 children provides a power of 0.87 to detect a Pearson’s correlation coefficient of >0.80 at a two-tailed alpha level of 0.05. Kraemer and Korner 21 suggest that the ICC is more powerful than the Pearson’s correlation coefficient; therefore, this sample size calculation is conservative.
The relationship (reflecting construct validity) between both the total scores on the PRT and laboratory measures (r = 0.65, p = 0.003) and the forward reach component and the anteroposterior limits of stability (r = 0.77, p < 0.001) were significantly associated. The relationship between the combined lateral reaches in the clinical test and the mediolateral limits of stability was more modest (r = 0.42, p = 0.08), and statistically non-significant. The Pearson’s correlation coefficient between the total score of the standing dimension of the PRT and steadiness was −0.79 (p < 0.001). The Pearson’s correlation coefficient between the total score of the standing dimension of the PRT and age was 0.83 (p < 0.001).
The relationship between the total score of the PRT and the GMFCS level was rs = −0.88 (p = 0.001). This analysis was repeated for the sitting and standing subscales, and Spearman’s correlation coefficients of −0.69 (p = 0.03) and −0.87 (p = 0.001) were obtained. Because the concurrent validity between the combined lateral reaches in the clinical test and the mediolateral limits of stability was not supported in the sample of children developing typically, analyses were also conducted for the different aspects of the standing dimension. Spearman’s correlation coefficients of −0.78 (p = 0.007) and −0.88 (p = 0.001) were obtained between the GMFCS and the anterior and combined lateral reaches of the PRT, respectively.
The results of the reliability testing are contained in Table 1. Exploration of item reliability was conducted with the data obtained between the two raters on the second occasion; these data are also contained in Table 1.
This study provides evidence that the PRT is a simple, valid, and reliable measure that can be used with children. Incorporation of a sitting component enables use with more diverse groups of children with cerebral palsy, including those who are unable to stand independently. Addition of lateral reach components in both sitting and standing, and permission to use orthoses and gait aides when administering the test, reflect functional aspects of balance in a more typical context than standing barefoot without aides. Evidence of concurrent and construct validity from children developing typically, and construct validity and reliability from children with cerebral palsy is discussed below.
On the basis of the significant, modest correlation coefficient between the sum of the reaches on the standing section of the PRT and the sum of the limits of stability, concurrent validity between the standing dimension of the clinical test and the laboratory-based measures is supported, at least for children developing typically. The relationship between the forward reach component of the clinical test and the anteroposterior limits of stability measure is much stronger than in other directions. This might be explained by variations in performance of the movement between the measures. For the clinical measure, the child can use any strategy to obtain maximal lateral reach, whereas children had specific instructions for the laboratory-based measure. Although detailed instructions were also given for the anteroposterior testing, their performance on the clinical measure seems to have resembled more closely the movement required in the laboratory. Duncan and colleagues 12 maintain that the reach test is more functional than a lean test and therefore are not concerned about this lack of support for concurrent validity of the lateral component. In a study with a sample of older women, Brauer and associates 16 obtained a correlation of 0.33 between the lateral reach test and the limits of stability in the lateral direction that are in the same low range as our values.
Our results support the construct validity of the standing section of the PRT based on significant correlations between steadiness and age. Sixty-two percent of the variance in the standing dimension was explained by steadiness. Sixty-nine percent of the variation in the standing section score is explained by age; younger children obtained lower scores on the test and older children obtained higher scores. This is substantially higher than the 38% of variance of the Functional Reach Test explained by age reported by Donohue and associates, 13 and might reflect the younger ages of the children and the addition of the lateral reach component used in the present study.
Support for construct validity of the PRT was also obtained by testing children with cerebral palsy and relating their scores to the GMFCS level. The negative correlation coefficient indicates that children who are less involved obtained higher total reaching scores. Importantly, in contrast to the lack of a significant relationship between the lateral reach components of the standing dimension and the mediolateral limits of stability among the children developing typically, the relationship with the GMFCS is greater for the lateral reach component (77% of the variance) than the forward reach component (61%) of the standing dimension when used with children with cerebral palsy.
In terms of reliability, the ICCs presented in Table 1 indicate that although Rater 2 conducted the assessments consistently between the test occasions, Rater 1 required more experience with the test. By the second test occasion, the raters obtained a high point estimate for reliability (0.93); however, the 95% confidence interval is wide due to the small sample of children in this part of the study. Both Donohue et al 13 and Niznik et al 14 report that little training is necessary for experienced pediatric physical therapists to conduct the Functional Reach Test. Our results suggest that exposure to working with children is desirable to know how to obtain optimal performance. Student participants commented that motivation seemed to be a key factor in the children’s performance. The student participants might not have had the skills to engage the child sufficiently to complete the task to the best of the child’s abilities; this skill is noted among master pediatric clinicians, 22 and likely takes time and experience to develop fully.
The strong interrater reliability coefficient obtained at the second test occasion permitted exploration of item reliability. Although the sitting dimension obtained a lower value than the standing dimension, the coefficients are sufficiently high to support the use of dimension scores (and total score) for both clinical and research purposes. In fact, all items except the forward reach component in sitting obtained ICCs >0.75, a value considered by Fleiss 23 to be excellent.
The evidence presented here supports the use of the PRT as a discriminative tool. Balance is perceived to be a component of movement that is modifiable through physical therapy intervention;24 however, responsiveness of this instrument has not yet been established to test this assumption. Before the PRT is used for evaluative purposes, responsiveness should be demonstrated on the target population. Sensitivity to change has been demonstrated with adults receiving rehabilitation when using the Functional Reach Test. 25 When tested and found to be responsive among children with cerebral palsy, the tool can be used to monitor change in status over time, while controlling for physical growth.
The PRT is a simple, valid, and reliable measure that can be used with children with cerebral palsy. Concurrent validity was supported in the sample of children developing typically based on force platform tests of limits of stability. Construct validity among children developing typically and children with cerebral palsy is supported. The measure has moderate-to-excellent test-retest reliability; however, inexperienced raters might benefit from further training or a second test occasion to optimize reliability. This measure is a discriminative tool that can be used with children with cerebral palsy. Sensitivity to change should be demonstrated before the PRT is used for evaluative purposes.
We thank Wendy Schrader, Leslie Morton, and Andrea Montreuil, physical therapists at the Cochrane-Temiskaming Children’s Treatment Centre, for their role in participating in the refinement of the protocol for testing of the PRT. The following students were BSc candidates at the time of the study and participated in this research as a part of the requirement of the degree: Sanjeev Bodwal, Shawn Campbell, and Amy St. Claire (for the validity testing with the children developing typically), Jeanne Carriere and Anne Wildhagen (for the reliability and validity testing of children with cerebral palsy), and Krista Leuschner (for participating with the photographs). Finally, we thank all of the children and their families for participating in this pair of related studies.
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Appendix A: ScoreSheet
Identification Number: __
Testing Protocol: Pediatric Reach Test
- a measuring tape (to measure height and foot length)
- a flexible, retractable measuring tape to measure distance reached (with loop to secure to child’s finger)
- a variety of wooden benches of different heights (or an adjustable bench) (child’s hips and knees should each be at 90 degrees when sitting)
The Pediatric Reach Test can be administered to cooperative and minimally involved children within 15 minutes. More time will be required to administer the measure to children with more severe involvement and those requiring motivational prompts.
Before testing, ensure that the child is wearing his or her regular footwear (i.e., orthoses—-if used, socks, and shoes) for both the sitting and standing sections and that the child’s regular mobility aide is used for the standing section. The therapist will demonstrate the task to the child and then the child will have one practice trial and one test trial (as per Niznick et al14). Children will be asked to “sit up tall” at the beginning of the test trial for each item. The initial and final positions will be held for three seconds each. Some children might need a reminder to reach as far as they can before starting the three-second count. Repeat the trial if the child either touches a wall or the therapist or takes a step.
Starting position: have the child sit on a surface (with no back or sides) with his/her feet flat on the floor, hips in neutral abduction/adduction, arms resting on the lap. Keep the sitting surface constant for each testing occasion. Child should not externally stabilize otherwise using the arms and/or legs. Be sure to spot appropriately for safety. Some children with severe physical involvement might need two people present (one to administer and one to spot).
First, ask the child to sit with hands in lap for 15 seconds. If a child can sit independently for 15 seconds, administer items 1, 2, and 3. Start by putting the loop at the end of the tape around the middle finger of the child’s dominant hand.
- Item 1. Ask the child to “sit up tall.” Then, with the tape secured on the finger, ask the child position his/her shoulder at 90 degrees of forward flexion with the elbow extended and the wrist in neutral (or as close to this position as possible). Position yourself stably behind the child and take an initial reading from the tape after the child has held the position for three seconds. Ask the child to reach as far forward as he/she can (toward a motivating object), and to hold the end position for three seconds. Measure the distance reached as designated by the difference between the initial and final positions.
- Item 2. Put the loop around the middle finger of the child’s distal right upper extremity. Ask the child to position his/her left shoulder at 90 degrees of abduction, with the elbow extended and the wrist in neutral (or as close to position as possible). Position yourself stably behind the child and take an initial reading from the tape after the child has held the position for three seconds. Ask the child to reach out to the right as far as he/she can, and to hold the end position for three seconds. Measure the distance reached as designated by the difference between the initial and final positions.
- Item 3. Repeat item 2 on the left side.
Starting position. Have the child stand as they normally do with regular footwear and gait aide. To maintain a constant position for the reaching tests, attach a sheet of paper (or Bristol board, as necessary) to the floor with masking tape, and trace the child’s foot position and also the gait aide contact points. This foot tracing should be used again for each of the interrater trials, as well as the retest trial (after the session, the foot length will be measured–perpendicular distance from the heel to the big toe). Safety concerns should be addressed as required.
First, ask the child to stand for 15 seconds. If a child can stand independently for 15 seconds, administer items 4, 5, and 6. Start by putting the loop of the tape around the middle finger on the child’s dominant hand.
- Item 4. Ask the child to position his/her shoulder at 90 degrees of forward flexion, with the elbow fully extended and the wrist in neutral (or as close to this position as possible). Position yourself stably behind the child and take an initial reading from the tape after the child has held the position for three seconds. Ask the child to reach as far forward as he/she can (toward a motivating object), and to hold the end position for three seconds. A child may lift a foot as long as it is replaced “approximately” over the traced foot print and the child has maintained balance throughout the reach (ie, not fallen or taken a step or relied on the therapist or a wall, etc). Loss of balance requires a retrial. Measure the distance reached as designated by the difference between the initial and final positions. For this item, it is not important whether movement is at the ankle or hip or both.
- Item 5. Put the loop of the tape around the middle finger on the right hand. Ask the child to position his/her left shoulder at 90 degrees of abduction, with the elbow extended fully and the wrist in neutral (or as close to this position as possible). Position yourself stably behind the child and take an initial reading from the tape after the child has held the position for three seconds. Ask the child to reach as far to the right as he/she can (toward a motivating object), and to hold the end position for three seconds. A child may lift a foot as long as it is replaced “approximately” over the traced foot print and the child has maintained balance throughout the reach (ie, not fallen or taken a step or relied on the therapist or a wall, etc). Loss of balance requires a retrial. Measure the distance reached as designated by the difference between the initial and final positions.
- Item 6. Repeat item 5 on the left side.
Note on motivation: The need for motivational prompts will vary among children, and is related to age and attention span, among other things. It might be useful to know a child’s interests and/or favorite toys or activities when administering this measure to young children (for example, finger puppets might be motivating for young children).
Recent research with the Functional Reach Test in standing used on children suggests statistically controlling for the base of support (through measures of foot length and distance between the feet in stance) and height of the child 26 if making either intersubject or intrasubject inferences; therefore, these variables were added to the score sheet to provide this option.
Similar to a strategy described by Westcott et al., 27 a total score is obtained by summing the interval data (score in centimeters).