IJSPT

ORIGINAL RESEARCH

FEASIBILITY AND RELIABILITY OF DYNAMIC POSTURAL CONTROL MEASURES IN CHILDREN IN FIRST THROUGH FIFTH GRADES Avery D. Faigenbaum1 Gregory D. Myer2,3,4 Ismael Perez Fernandez5 Eduardo Gomez Carrasco5 Nathaniel Bates2 Anne Farrell1 Nicholas A. Ratamess1 Jie Kang1

ABSTRACT Purpose/Background: Although dynamic postural control is a prerequisite to the development of fundamental movement skills in children, few studies have examined the feasibility and reliability of assessment techniques that measure dynamic postural control in youth under 13 years of age. Therefore, the purpose of this study was to determine the feasibility and reliability of the Lower Quarter Y Balance Test (YBT-LQ) in children and to examine the reproducibility of these measures across developmental periods of childhood. Methods: 188 subjects in first through fifth grades (age = 6.9 to 12.1 yr) performed the YBT-LQ on two occasions in a field-based setting. Reach distances and cumulative score (sum of 3 directions) were measured and analyzed using intraclass correlation coefficients (ICC). Sub-cohorts of 14 and 8 subjects were used to assess inter-rater reliability within-session and between-session, respectively. Results: The overall ICC was moderate-to-good for the anterior (right=0.82; left=0.82), posteromedial (right=0.77; left=0.75), and posterolateral (right 0.80; left=0.77) reach directions. The combined ICC was also moderate-to-good for children in grades 1 (0.71), 2 (0.74), 3 (0.84), 4 (0.82), and 5 (0.79). Typical error values for right and left limbs were less than 10% of the mean for all reach measures across all grades. Interrater reliability within session (ICC > 0.995) and between sessions (0.907 ≤ ICC ≤ 0.974) were both excellent. No unexpected responses or injury occurred during testing. Conclusions: These findings indicate that the YBT-LQ is a feasible and reproducible measure of dynamic postural control in children in first through fifth grades. Level of Evidence: 2b Key Words: Assessment, balance, postural stability, skill-related fitness, youth

1

The College of New Jersey, Ewing, New Jersey, USA Cincinnati Children’s Hospital Medical Center, Division of Sports Medicine, Cincinnati, Ohio, USA 3 Department of Pediatrics and Orthopaedic Surgery, College of Medicine, University of Cincinnati, Ohio, USA 4 The Micheli Center for Sports Injury Prevention, Waltham, Massachusetts, USA 5 Universidad Europea de Madrid, School of Physical Activity and Sport Science, Madrid, Spain 2

Grant Support: American Council on Exercise Institutional Review Board Approval: The Institutional Review Board at The College of New Jersey approved this study (protocol number 1118-06) on September 29, 2011.

Acknowledgements: This study was supported by a grant from the American Council on Exercise. The authors thank Bud Kowal, Eileen Kowalsky and the Ewing Township School District (NJ) for their support of this research study. The authors also thank Joelle Bagley and Shannon Boise for their assistance with data collection

CORRESPONDING AUTHOR Dr. Avery Faigenbaum, Ed.D, CSCS, FACSM, FNSCA Department of Health and Exercise Science The College of New Jersey 2000 Pennington Rd Ewing, NJ 08628 USA Email: [email protected]

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INTRODUCTION A variety of fitness test batteries are currently used to assess physical fitness and sports performance in youth.1-3 Data from these tests can be used to specifically target areas in need of improvement and educate youth about the importance of regular participation in a variety of fitness activities. Moreover, clinicians use fitness test data to identify young athletes at increased risk of injury and design conditioning programs to enhance sports performance. Despite the popularity of field-based measures such as the one-mile run and push-up test, the use of skillbased measures that require dynamic postural control have received less attention in children. The lack of data on skill-based testing in youth is noteworthy since low competency in fundamental movement skills is strongly associated with lower cardiorespiratory fitness during the growing years.4 Furthermore, youth who have not mastered fundamental movement skills may be less likely to participate regularly in organized sports and play experiences.5 These findings have important public health implications since low levels of habitual physical activity have been found to increase the risk of injury in children during physical education class, leisure time activity, or sport.6 Moreover, youth who do not develop at least a basic level of motor skill performance by the end of adolescence may be less likely to demonstrate at least fair levels of health-related fitness in early adulthood.7 The ability to stabilize the body and maintain postural control during dynamic actions is critical for the successful performance of fundamental movement skills such as kicking and jumping. One tool that assesses dynamic postural control is the Lower Quarter Y Balance Test (YBT-LQ).8 The goal of the YBT-LQ is to maintain single-leg stance balance while reaching as far as possible with the contralateral leg in the anterior (AT), posteromedial (PM) and posterolateral (PL) directions. The available data indicate that tests of dynamic postural control are reliable for measuring single leg excursion distances in adolescents and adults.8-10 For example, Plisky et al. examined the reliability of the YBT-LQ in collegiate soccer players and reported intraclass correlation coefficients (ICC) for intrarater and interrater reliability between 0.85 to 0.91 and 0.99 to 1.00, respectively.8

Despite the importance of dynamic postural control as a prerequisite to the development of fundamental movement skills in children, to the author’s knowledge no data on the reliability of unilateral dynamic balance in school-age youth under 13 years of age are available. Similarly, of the few studies that examined balance in children,11,12 no studies have assessed the ability of children in grades 1 to 5 to perform a unilateral dynamic balance test that requires strength, flexibility, and proprioception. Since reliable tests are the foundation of the ability to properly assess and monitor children’s fitness and performance, additional research is needed to determine the reliability of unilateral dynamic balance in children and to examine the reproducibility of these measures throughout early childhood. This information is particularly important relative to the growing interest in physical fitness testing and injury prevention strategies in youth.13,14 Therefore, the purpose of this study was to determine the feasibility and reliability of the YBT-LQ in children in first through fifth grades, and to examine the reproducibility of these measures across developmental periods of childhood. METHODS Participants Study participants were a convenience sample of 188 children attending an urban public school in New Jersey, USA, between 2011 and 2012. Children (97 male, 91 female) in grades one (n= 42), two (n = 37), three (n = 22), four (n = 43) and five (n= 44) volunteered to participate (Table 1). Participants had no prior experience performing the YBT-LQ. Exclusion criteria included any lower extremity injury, medical condition, or disability that limited participation in physical activity. This study was approved by the Institutional Review Board at The College of New Jersey as well as the administration at the participating school. All parents provided written permission and all children provided assent before the start of the study. Study Protocol All participants (n = 188) performed the YBT-LQ on two occasions separated by 7 to 10 days in a school gymnasium. A rater assessed each participant’s standing height to the nearest 0.5 cm on stadiometer and body mass in light clothing to the nearest 0.1 kg

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Table 1. Demographic and anthropometric characteristics of study participants

using a digital scale. Prior to formal testing, subjects performed 3 minutes of calisthenics (e.g., jumping jacks and standing march) and six practice trials on each leg in each of the three reach directions. Due to the amount of time needed for administering the YBT-LQ to a large group of children, three practice trials were performed in a group setting (rater-tochild ratio of 1 to 5) using floor tape in a Y-shape and a small foam box as the reach indicator. During these practice trials, raters highlighted the importance of maintaining single-leg stance and participants practiced the desired action in three reach directions on both legs. Three additional practice trials as well as all formal YBT-LQ procedures were performed on a commercially available Y-Balance kit (Move2Perform, Evansville, IN) under close supervision (raterto-child ratio of 1 to 1). Five testing stations were present and participants were tested in groups of 20 to 25. Raters who completed an online YBT-LQ certification and had experience administering the YBTLQ served as administrators.

In order to assess interrater reliability (observer error), two raters who were blinded to each other’s scoring simultaneously observed and rated a single trial performance on a subsample of 14 participants in this study. In addition, interrater reliability (performance error) was assessed by two different raters who scored 8 participants performing separate trials of the YBT-LQ for each rater on the same day. The Y-Balance kit consists of a stance platform to which three pieces of polyvinylchloride pipe are attached in the AT, PM, and PL reach directions (Figures 1a,1b, and 1c). Each pipe is marked in 0.5 cm increments for measurement. To perform the YBTLQ, the participant stood on one foot on the center foot plate with the most distal aspect of the toes just behind the starting line. The starting position for the reach foot was between the center foot plate and the pipe opposite the stance foot. While maintaining single-leg stance, the participant was instructed to push the reach indicator along the pipe with the reach foot as far as possible in the direction being tested; and then return the reach limb to the starting position resuming a bilateral stance. Participants were not given specific strategies to enhance performance. The maximal reach distance was measured by reading the tape measure at the edge of the reach indicator, at the point where the most distal part of the foot reached in half centimeters. The reach was discarded and repeated if the subject failed to maintain unilateral stance on the platform, failed to maintain reach foot contact with the reach indicator, used the reach indicator for stance support or failed to return the reach foot to the starting position under control. The testing order was three trials standing on the right foot reaching in the AT direction followed by three trials standing on the left reaching in the AT direction. This procedure was repeated for the PM and the PL directions. The specific testing order was right AT, left AT, right PM, left PM, right PL, and left PL. If a proper reach was not performed in three trials for any direction, an additional three trials were allowed. The furthest successful reach for each direction was used as an indication of dynamic postural control and for analysis. A total combined score was based on the sum of performance in three reach directions on both legs. Each participant wore the same athletic shoes during testing sessions.

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Figure 1. Figures 1a, 1b, 1c, Performance on the Y balance test in the anterior (1a), posteriomedial (1b) and posterolateral (1c) reach directions.

In order to make the testing experience more enjoyable and age-appropriate for children, we modified the YBT-LQ and created a game called the “sleeping alligator” whereby the participants imagined they were a bird standing on a small island (center foot plate) and all around them was swampy water (the floor) filled with alligators (the three reach indictors). As a pedagogical cue, subjects were reminded to slowly push the alligators away using one foot while maintaining balance so they would not fall into the swamp. We placed child-friendly alligators made from green cloth on top of each reach indicator. YBT-LQ procedures (including warm-up trials) took approximately 10 minutes per participant. Data Analysis The data were analyzed for each subject, in each grade, for the right and left leg in the AT, PM and PL directions. In addition, a total combined score, which was based on the sum of performance in the three reach directions on each leg, was analyzed by grade. Descriptive statistics were calculated for all variables. The relative reliability of the data was determined using intraclass correlation coefficients (ICC, 3,1). Interrater reliability was calculated for two different scenarios. ICCs were calculated for separate raters’ evaluations of the same subject performing the same trial and separate raters’ evalua-

tions of the same subject performing separate trials within the same session. These calculations defined the reliability for observer error within-trial and the subject performance error between-trials, respectively. Single-rater, between-session reliability was also calculated for each individual grade level. The range of ICC values was described using the classifications of Fleiss, where ICC < 0.4 was considered poor, 0.4 < ICC < 0.75 was considered fair-to-good, and ICC > 0.75 was considered excellent.15 Typical error analyses (square root of mean square error) were also used to evaluate reliability as typical errors can help establish the range at which differences in absolute values become clinically significant16. Data are reported as means and SDs and statistical significance was set at p < .05. Statistical procedures were performed using SPSS version 17.0 for windows (Chicago, IL) and SAS version 9.1 (SAS Institute, Cary, NC). RESULTS All participants completed the aforementioned study procedures as described. No unexpected events or injury were reported. Performance data for each grade, represented as means and standard deviations in centimeters of the maximal reach distance for the AT, PM, and PL reach directions while standing on the right and left foot for both testing trials, are presented in Table 2.

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Table 2. Performance data for each grade, represented as means and standard deviations in centimeters of the maximal reach distance for the anterior, posteromedial, and posterolateral reach directions while standing on the right and left foot for testing session 1 and 2

Interrater reliability within session, within trial (Observer Error) When different raters observed the same participant performing the same test trial, the interrater ICCs for the YBT were excellent for all variables. Testers demonstrated nearly perfect correlation as ICCs were all greater than 0.995 for the AT, PM, PL and composite directions on both the right and left limbs. There was no side-to-side difference observed in these ICC measures. Typical “observer” error for each individual reach variable was between 0.14–0.61 cm, which was less than 1% of the total range for shortest reach variable. Composite typical error was 0.98 for the right leg and 0.92 for the left leg, both of which were less than 0.4% of the total range of composite reach. Interrater reliability within session, between trials (Performance Error) When different raters observed the same participant performing separate test trials, the inter-rater

ICCs for the YBT were also excellent for all variables tested. ICCs ranged between 0.907–0.990 for AT, PM, PL and composite reach on both limbs when separate test instances were examined. The combined inter-rater ICCs were nearly identical between sides as the right limb value was 0.947 and the left limb was 0.949. Typical “performance error” for each individual reach variable was between 1.51–2.53 cm, which individually represented less than 3.3% of the total range of reach for each variable. Composite typical error was 2.68 cm for the right leg and 3.13 cm for the left leg, both of which were less than 1.5% of the total range of composite reach. Single-rater between-session reliability by grade level For subjects of all grades, the overall ICC was moderate-to-good for the AT (right = 0.82; left = 0.82), PM (right = 0.77; left = 0.75), PL (right = 0.80; left = 0.77) and composite (right = 0.88; left = 0.88) reach

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Table 3. Intraclass correlation coefficients (ICC) and typical error by grade

directions. The combined ICC was also moderate-togood for participants in grades 1 (0.71), 2 (0.74), 3 (0.84), 4 (0.82), and 5 (0.79). Typical errors for individual and composite leg reach variables on the YBT-LQ are represented for each grade level in Table 3. Typical error values were less than 10% of the mean for all reach measures across all grade levels. These relative percentages of error were largest within the first grade population (8.0%), decreased through third grade (4.8%), and leveled off in fourth (5.4%) and fifth grades (5.9%). For all grade levels, typical error during the AT reach (3.49 cm) was less than the PL (4.97 cm) and PM (4.89 cm) reaches which were less than the composite (9.20 mm) reach. No correlation between change in grade level and increase or decrease in typical error values was identified. However, participants in third grade demonstrated the lowest typical error values for all individual reach variables. Typical error for individual and composite reach measures across the study population did not demonstrate differences in excess of 0.52 cm between the right and left limbs. When the population was broken down by grade level, performance differences in typical error between right and left limbs were very similar and exceeded 1.0 cm for only fourth grade PL and fifth grade PM directions. DISCUSSION Since motor skill competence early in life appears to form the foundation for a lifetime of physical activity,7,17 it is increasingly important to establish reliable assessments that can be used to monitor and

assess skill-related fitness components in children. The current study examined the reliability of the YBT-LQ in children in first through fifth grades in a field-based setting. The present findings support the results of others who examined the reproducibility of postural control assessments in adolescents and adults,8-10 and indicate that the YBT-LQ is both a feasible and reliable assessment of unilateral balance and dynamic neuromuscular control in healthy children. In this investigation, 188 children performed the YBT-LQ on two occasions following standardized procedures and no untoward events were reported. Importantly, the reproducibility of unilateral dynamic balance performance was found to be relatively consistent in a large sample of children in grades one to five, and this could have important implications for assessing motor control development in school-age youth. However, it must be underscored that performance on the YBT-LQ was evaluated by trained raters who consistently followed standardized testing procedures. Although data on test-retest reliability of unilateral dynamic balance in children is limited, the current findings are supportive of previous reliability assessments in cohorts of older subjects.8-10 For example, Filipa et al. noted intrarater ICCs of 0.81 to 0.96 for the three reach directions in adolescent athletes9 and Plisky et al. reported intrarater ICCs from 0.82 to 0.87 for the three reach directions in a sample of high school basketball players.10 Geldhof et al. reported ICCs between 0.62 to 0.80 in 9 to 10 year old children who performed a clinical test of postural stability (Balance Master) that quantified static

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and dynamic standing balance using a portable force plate.12 Of note, in the current study, ICCs were greater for the overall population than the sample populations for each grade level. As the number of subjects within a population increase, the variance is likely to decrease as outlying cases will be muted by the increased weight of the overall population mean. In the present investigation, the sample populations had approximately five times fewer subjects than the overall population. This demographic could have allowed outliers to increase the relative variability within each grade level, which would decrease the ICC values. This phenomenon can again be seen as the composite ICC values for each grade level were greater than any of the ICCs reported for individual measures within that grade level. In the current study, the composite reach variable expressed both greater ICC correlations and greater error than individual reach measures. This finding corresponds with previous Y-Balance Test reliability studies performed on active military personnel.18 Although the magnitude of error in the composite measure increased compared to the individual reach measures, it represented a smaller percentage of change than was seen in the score magnitude between an individual and composite reach. Therefore, the composite values demonstrated the most reliable ICCs. The typical error for individual and composite reach measures across the study population did not demonstrate side-to-side differences. However, when the population was broken down by grade level, side-toside differences in typical error exceeded 1.0 cm in selected grades and reach directions. Although other researchers reported no difference in unilateral postural stability between dominant and non-dominant limbs in healthy young adults,19,20 the current observations are important to physical therapists and other clinicians who use side-to side comparisons to assess performance or identify aberrant motor control patterns as increased error is typically indicative of reduced control.21,22 The relative measures of typical error for the right and left limbs were largest within the first and second grade populations (Figure 2). Participants in third grade demonstrated the lowest typical error values

Figure 2. Typical error as a percentage (%) of mean reach distance for the right (top) and left (bottom) limbs.

for individual reach variables on their right limb, whereas relative measures of typical error for the left limb in the anterior and posterior-lateral reach directions were lowest in the fifth grade population. While the maturation of the neurological, visual, vestibular and proprioceptive systems are important considerations when evaluating balance performance during the growing years,11 factors related to somatotype, habitual physical activity, and mental engagement should also be considered. Basic motor skills are reaching mature form between five and eight years of age,23 and these skills continue to be refined and improved as the child finds new solutions to efficient movement. Also, changes in somatotype during early childhood which are characterized by a redistribution of subcutaneous adipose tissue, the development of muscle tissue, and the lengthening of the legs relative to stature may influence postural stability in children.23,24 Age-related improvements in motor skill performance and muscle strength may have had an observable influence on dynamic balance in the current investigation. The YBT-LQ is a relatively challenging assessment that requires strength, flexibility, proprioception, and concentration coupled with motion at the ankle, knee and hip joints. Each reach direction requires different activation of the lower extremity muscles25. In addition, trunk motion is required as the child attempts to maximize reach distance in different directions. As the foot reaches in the targeted direction, the child’s center of mass is moved in rela-

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tion to the base of support and adequate neuromuscular control is needed to consistently perform the test. Due to environmental as well as maturational influences, children entering third grade (about nine years of age) may have developed more efficient movement strategies and muscle strength that could be applied to a constrained task that required postural control and balance. Younger subjects may not have developed the motor control necessary to consistently reproduce dynamic motions and therefore may be likely to express lower reliability score in measures of dynamic postural control. From a practical perspective, youth fitness tests should be able to detect small but significant changes in performance and provide meaningful information to clinicians and pediatric researchers. The current findings indicate that the methods employed in this study are feasible and reliable for assessing dynamic postural control performance in children in a fieldbased setting, although raters should be mindful of the challenges associated with administering fitness tests to young children. The reproducibility of the test and acceptable measurement error in this study was likely due to a number of factors. As per standard YBT-LQ testing guidelines, all participants had an opportunity to become familiar with the test and practice the desired movements while receiving constructive feedback on the quality of their performance from a trained rater. A standard testing order was followed and well-defined criteria were used to define a successful reach. Also, the YBT-LQ was modified by using the “sleeping alligator” game as a pedagogical cue in order to stimulate interest in the desired task, maintain attention, and make the experience enjoyable for the children. Despite the growing interest in the relationship between health- and skill-related fitness measures in school-age youth, normative data for dynamic balance in children are not yet available for comparison. Nevertheless, these findings indicate that the YBT-LQ can be used to quantify unilateral dynamic balance performance in healthy children in grades 1 to 5. Although these findings may not be generalizable to children with physical limitations, administration of dynamic balance assessments in field-based settings could be used to teach children about skill-related components of physical fitness and identify children

at increased risk of injury. Moreover, due to low levels of fundamental movement skill competency in children,26 the assessment of dynamic postural control may be an important measure in interventions designed to promote physical activity and improve fitness performance in school-age youth. In the present investigation, grade level and chronological age were used instead of maturational age and we recognize that growth and maturation can influence fitness performance during childhood. CONCLUSION To the author’s knowledge, no other study has examined the feasibility and reliability of the YBT-LQ in children. Measures of inter-rater reliability were substantial and test-retest reliability scores in children in first through fifth grades were consistent over 7 to 10 days. Typical error values were less than 10% of the mean for all reach measures across all grade levels and these observations could be considered clinically significant. These substantive findings fill the gap of prior literature that focused on measures of dynamic balance in adolescents and adults, and provide valuable information for the use of this dynamic postural control assessment as a tool to quantify normal motor control development in healthy children. Since compromised stability and poor postural control may hinder a child’s ability to master fundamental movement skills and, in turn, participate in recreational and sporting activities as an ongoing lifestyle choice, further research is recommended to establish age-related strategies to enhance dynamic balance and postural control in school-age youth. REFERENCES 1. Institute of Medicine (IOM). Fitness Measures and Health Outcomes in Youth. Washington, DC: The National Academies Press; 2012. 2. President’s Council on Physical Fitness Sports and Nutrition. Physical Educator Resource Guide; 2012. 3. Faigenbaum A, Westcott W. ACE Youth Fitness Manual. San Diego, CA: Americn Council on Exercise; 2013. 4. Hardy L, Reinten-Reynolds T, Espinel P, Zask A, Okely A. Prevalence and correlates of low fundamental movement skill competency in children. Pediatrics. 2012;130:e390-e398. 5. Okely AD, Booth, M., Patterson J. Relationship of physical activity to fundamental movement skills

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16. Ford K, Myer G, Hewett T. Reliability of landing 3D motion analysis: implications for longitudinal analyses. Med Sci Sports Exerc. 2007;39:2021-2028. 17. Barnett L, Van Beurden E, Morgan P, Brooks L, Beard J. Does childhood motor skill proficiency predict adolescent fitness? Med Sci Sports Exerc. 2008;40:2137-2144. 18. Shaffer S, Teyhen D, Lorenson C, Warren R, Koreerat C, Straseske C. A reliability study involving multiple raters. Military Med. 2013;178:1264-1270. 19. Hoffman M, Schrader J, Applegate T, Koceja D. Unilateral postural control of the functionally dominant and nondominant extremities of healthy subjects. J Athl Train. 1998;33:319-322. 20. Lin W, Liu Y, Hsieh C, Lee A. Ankle eversion to inversion strength ratio and static balance control in the dominant and non-dominant limbs of young adults. J Sci Med Sport. 2009;12:42-49. 21. Myer G, Martin L, Ford K, et al. No association of time from surgery with functional deficits in athletes after anterior cruciate ligament reconstruction: evidence for objective return-to-sport criteria. Am J Sports Med. 2012;40:2256-2263. 22. Paterno M, Ford K, Myer G, Heyl R, Hewett T. Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction. Clin J Sports Med. 2007;17:258-262. 23. Malina R, Bouchard C, Bar-Or O. Growth, Maturation and Physical Activity. 2nd ed. Champaign, IL: Human Kinetics; 2004. 24. Lee A, Lin W. The influence of gender and somatotype on single leg upright standing postural stability in children. J Appl Biomech. 2007;22:173-179. 25. Earl J, Hertel J. Lower extremity muscle activation during the Star Excursion Balance Test. J Sports Rehabil. 2001;10:93-105. 26. Hardy L, Barnett L, Espinel P, Okely A. Thirteenyear trends in child and adolescent fundamental movement skills: 1997-2010. Med Sci Sports Exerc. 2013;45:1965-1970.

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Feasibility and reliability of dynamic postural control measures in children in first through fifth grades.

Although dynamic postural control is a prerequisite to the development of fundamental movement skills in children, few studies have examined the feasi...
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