The effect of footwear and sports-surface on dynamic neurological screening for sport-related concussion

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1 Available online at Journal of Science and Medicine in Sport 13 (2010) Original paper The effect of footwear and sports-surface on dynamic neurological screening for sport-related concussion Anthony G. Schneiders a,, S. John Sullivan a, Johan Kvarnström b, Maria Olsson b, Tobias Ydén b, Stephen Marshall c a Centre for Physiotherapy Research, University of Otago, New Zealand b Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Sweden c Department of Epidemiology, University of North Carolina,USA Received 11 August 2009; received in revised form 7 January 2010; accepted 18 January 2010 Abstract The Sport Concussion Assessment Tool (SCAT) is a standardised global assessment for the identification of sport-related concussion (SRC). An integral component of the SCAT is the neurological screen, which contains the assessment of motor performance including gait evaluation. However, it is not known how performance of gait is affected by the surface/footwear interactions encountered in various sporting environments. The purpose of this study was to investigate the effect of footwear and sporting surface on the time to perform a standardised Tandem Gait (TG) task. One hundred and eight amateur athletes were recruited, and three common sports-surfaces (grass, hardwood court, artificial turf) were compared. All groups were tested barefoot and with sports-surface specific footwear. Mixed model ANOVA, controlling for covariates and including a post hoc Bonferroni procedure, was used to investigate the influence of footwear and sports-surface on TG time. The study demonstrated that times for a defined TG task in healthy athletes depended on footwear, sports-surface, and the specific athletic population. The study demonstrated a significant interaction (F 2,104 = 3.35, p = 0.039) between groups (grass, hardwood court and artificial turf), and times were faster wearing footwear compared to barefoot (F 2,138 = 26.31, p = 0.001). In contrast to the footwear conditions, there was no statistical difference between the barefoot conditions on any of the sport-surfaces. These findings suggest that clinicians should standardise footwear and the testing surface at baseline in order to accurately assess motor performance tests when SRC is suspected Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. Keywords: Brain concussion; Footwear; Performance; Tandem Gait; Measurement 1. Introduction Concussion and mild traumatic brain injury (mtbi) are common injuries in contact and collision sports, 1 3 however, it has been noted that many concussions go undetected and unreported. 4 6 Unreported concussions are serious because they increase the likelihood of athletes continuing to practice and play, placing themselves at risk of a subsequent and possibly more serious injury. Valid and reliable screening tools are therefore essential in assisting the sports medicine professional in recognising a concussion. Corresponding author. address: tony.schneiders@otago.ac.nz (A.G. Schneiders). The International Concussion in Sport Group is developing a standardised screening and assessment tool for the sideline screening of sport concussion. 7 The Sport Concussion Assessment Tool (SCAT) was designed to assess a number of specific concussion indicators including physical signs and symptoms; memory and cognitive performance; and a neurological screen of motor performance. The updated SCAT2 recommends a qualitative measurement of gait performance; however, there is no specific assessment protocol associated with the item and it is thus open to differing interpretations. This issue has been recently addressed by the introduction of a timed Tandem Gait (TG) task 8 that evaluates locomotion, dynamic balance and lower limb coordination. The test requires the individual to walk in a heel toe manner along a /$ see front matter 2010 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. doi: /j.jsams

2 A.G. Schneiders et al. / Journal of Science and Medicine in Sport 13 (2010) m line, turn and return to the starting position as quickly as possible without losing their balance. The TG task has been shown to be reliable in young non-concussed barefoot individuals in a controlled environment and norms have been developed. 9 Testing environment, 10 footwear, 11 and support surface 12,13 have all been shown to affect the measurement of balance and gait performance. It has been demonstrated that balance testing using the Balance Error Scoring System (BESS), which is frequently used in the screening and assessment of a concussion, 7,14 is affected by the environment in which it is administered. Athletes are often screened in settings such as; emergency rooms, changing rooms or on the sidelines, and often the sports-surface and footwear are specific to the sport. Improved scores were obtained when the BESS was administered in a locker room environment in comparison to when it was administered on the sideline during sports participation. 10 This finding has implications for the interpretation of performance scores in a potentially concussed athlete who may be assessed serially in different environments and conditions, and potentially by different health care providers. The types of footwear and surface have been shown to affect performance during gait assessment, with participants walking faster with shoes 11 and slower when walking on irregular surfaces. 12 Therefore, it is vital to understand the difference in performance of a potential concussion screening task such as TG when measured under different environmental conditions. The purpose of this study was to investigate the effect of footwear and sporting surface on the time to perform the standardised TG motor performance task. 2. Method 2.1. Participants Healthy active males and females aged between 16 and 35 yrs were recruited from amateur sport teams and community sport centres in a metropolitan area in southern New Zealand. Participants were recruited into the study based on the type of surface (grass, hardwood court, artificial turf) they regularly played on. Participants were excluded if they had suffered a recent (<6 mths) head injury or had a known neurological or musculoskeletal condition. Individuals who had recently finished a session of intense physical activity were also excluded. Participants gave written informed consent to be involved in the study and approval was obtained from the University of Otago, Human Ethics Committee Task The TG task 8,9 required participants to perform a tandem (heel toe) gait along a 3-m line, turn 180 and return to the starting position in the same heel toe manner. Task instructions were standardised, the task was demonstrated, and participants were instructed to walk as quickly and as accurately as possible while maintaining contact with the line. No practice was allowed. The trial was counted as a fail and was repeated if the feet lost contact with the line. Three trials of each condition were measured with a manually operated digital stopwatch accurate to 0.01 s (Oregon Scientific, Portland, OR). Prior to main data collection, a study was undertaken to determine the inter-rater reliability of the timed TG task measure recorded by three members of the research team who tested all participants Testing surface The TG task was performed on three surfaces chosen to simulate a number of sideline assessment sports environments. The surfaces were: (1) grass (rugby/football field); (2) hardwood court (basketball); (3) artificial grass/turf (Tiger- Turf WETT TM ) and participants wore their usual footwear for playing on each surface: (1) rugby/football boots; (2) court shoes/cross trainers and; (3) turf shoes/cross trainers, respectively. Each group of subjects was only tested on the surface they regularly played on and not on every surface. The tests were performed on the sideline of the sports field/court during team practice sessions. An adjacent firm concrete/asphalt surface was also used for testing to simulate the surface in an assessment environment such as an emergency room, stadium corridor/tunnel or walkway. Ground hardness was measured on the grass surface using an industry penetrometer (Eijkelkamp, model 06.01; Giesbeck, Netherlands). Average hardness values 15 were calculated from four days across the testing week using the average of 3 measurements from 7 points spaced 0.5 m along the 3-m TG line Procedures For the grass and artificial turf surfaces, participants performed the TG task under two footwear conditions and on an additional surface: (1) wearing sports footwear; (2) barefoot and; (3) barefoot on an adjacent concrete surface. For the court surface, the test was performed both barefoot and wearing sports footwear, and an adjacent concrete surface was not utilised due to the fact that the court surface was considered comparable to concrete in terms of relative hardness. The testing order on all three surfaces was randomised to control for potential learning effects. Participants were given short recovery breaks (20 s) after each trial and between each condition. Data were collected within a week for each testing surface during stable climatic conditions, with outdoor testing occurring at a set time in the afternoon Data analysis The mean score of the three trials for each condition was determined for each participant. The primary analysis employed a 3 2 mixed model ANOVA

3 384 A.G. Schneiders et al. / Journal of Science and Medicine in Sport 13 (2010) Table 1 Characteristics of participants grouped by primary sports-surface. Sports-surface Age (yrs) Sex Height (cm) Weight (kg) BMI Mean ± SD Male:female Mean ± SD Mean ± SD Mean ± SD Grass ± : ± ± ± 2.53 (N = 36) Court ± : ± ± ± 2.68 (N = 36) Artificial turf ± : ± ± ± 2.56 (N = 35) Group difference F 2,104 = p = χ 2 = p = F 2,104 = 4.24 p = F 2,104 = p = F 2,104 = p = (groups conditions) to investigate the role of surface and footwear. A 2 2 mixed model ANOVA investigated barefoot performance on the different surfaces. All post hoc analysis was performed using a Bonferroni procedure and the alpha level was fixed at Descriptive statistics were calculated for age, weight, height, sex and BMI. Intra-class Correlations (ICC) statistics were calculated prior to the main study for combinations of raters. All analysis was performed using SPSS version Results Thirty-six participants were recruited from each of three sporting environments (groups). No participants failed any trial via our criteria, however, one participant in the artificial turf group produced atypically slow times (>35 s), which indicated that they were most probably not following the instructional set, and their data were removed from further analyses. The characteristics of the participants are presented in Table 1. The three groups were comparable (p > 0.05) with respect to age, weight and BMI while the artificial turf group was shorter (p = 0.03) than the other two groups (F 2,105 = 4.76, p = 0.011) which likely reflects the higher ratio of females in this group. In contrast to the turf participants, the grass and court groups were predominantly male. The mean stud/cleat length of the football boots worn on grass was 14.6 ± 3.2 mm and the mean ground hardness was 56 (±9.6) N/cm 2 with these results included primarily to allow study replication. Inter-rater reliability of TG timed measurement for combinations of raters resulted in ICC (2, 1) values ranging from of 0.96 (C.I ) to 0.99 (C.I ). The TG task times for the various conditions are presented in Tables 2 and 3. In the 3 2 ANOVA there was a significant main effect by condition (F 2,138 = 26.31, p = 0.001) with all 3 groups faster with footwear than barefoot (Table 2). This difference was greatest in the artificial turf and court athletes resulting in a significant group condition interaction (F 2,104 = p = 0.039). In the 2 2 ANOVA there was no difference between the two barefoot conditions within each environment (F 1,69 = 0.10, p = 0.751) (Table 3.). Examination of the two barefoot conditions for the grass and artificial turf groups showed a significant interaction (F 1,69 = 15.66, Table 2 Tandem Gait time(s) for sports-surface and footwear conditions. Sports-surface Test condition Footwear Barefoot Grass (N = 36) Mean ± SD ± ± 3.08 Range Court (N = 36) Mean ± SD ± ± 3.18 Range Artificial turf (N = 35) Mean ± SD ± ± 2.55 Range Table 3 Tandem Gait time(s) for sports-surface groups during barefoot conditions. Sports-surface group Test condition Barefoot on sports-surface Barefoot on concrete Grass (N = 36) Mean ± SD ± ± 2.75 Range Artificial turf (N = 35) Mean ± SD ± ± 3.41 Range p = 0.000) with the artificial turf athletes slower. It is noted that despite the standard deviations of the mean values being relatively tight, the distributions (range) do overlap between all conditions which reflects some variability in task performance that should be taken into consideration when interpreting the results. 4. Discussion The results demonstrated that performance on the timed TG task varied significantly with the nature of the sporting group or surface and whether participants were barefoot or shod. Footwear (boots or sports shoes) resulted in a faster performance than when the TG task was performed barefoot. Likewise, times varied between each sporting environment which might suggest that the sporting surface or the type of athletes played a role in TG performance.

4 A.G. Schneiders et al. / Journal of Science and Medicine in Sport 13 (2010) The reason for the significantly faster performance on all testing surfaces while wearing footwear is speculative. The logical and practical explanation for decreased speed when walking heel toe barefoot could be that the participants were more careful to avoid standing on their toes and therefore walked more carefully (slowly). Likewise, the higher level of sensory feedback while performing barefoot 16 could have created a more careful gait pattern in fear of getting hurt. Additionally, shoes might provide a larger base of support and could afford additional stability during dynamic balance and coordination tasks. The enhanced performance while wearing footwear has been demonstrated by others during traditional gait and balance tasks, 11,17 illustrating that the footwear provides some form of protective function and/or confidence to the user, allowing them increased speed and accuracy. The lack of difference between the barefoot conditions on grass/artificial turf and concrete suggests that the change in surface was not a distinguishing factor and justifies our decision not to test an alternative firm surface (concrete) within the hardwood court environment. The fact that barefoot times did not significantly change between firm and more compliant surfaces also suggests that the physical, sporting and psychological characteristics of each sports group were more likely responsible for the difference in performance observed between environments. Previous data on TG in young persons has been generated while walking barefoot or with sports shoes in a clinical laboratory environment. 8,9 The TG times reported in this present study are slower than those previously reported when walking with 8 or without shoes, 9 despite the firm court and concrete surfaces approximating the laboratory (vinyl on concrete) surface of the former studies. The differences observed might therefore reflect the sports environment, with increased participant distraction due to other competing and concurrent activities, noise and varying climatic conditions. This finding is in keeping with a recent study which measured static balance using the BESS in different environments 10 and demonstrated that sideline testing resulted in decreased performance compared to a controlled clinical environment (locker room). Our data adds to the argument that repeated measurement of standardised tests must also take into account when and where the measures are obtained. As the TG task has the potential to be used as both a preseason assessment and for the monitoring of recovery in SRC, it is important that the conditions surrounding each assessment are well documented to assist in the interpretation of the subsequent scores. A difference in TG performance between sporting groups was also identified in this study. The participants were persons who currently were playing sport in each of the three environments and the ages, weights and BMI were comparative between the groups. While gender differences were not balanced in two (grass and hardwood court) of the three groups and might have affected the results, the gender ratio is typical of the sports studied (rugby, football, basketball) and the higher percentage of males who sustain a concussion. 18 In a preliminary study by the authors, 8 females were shown to be significantly slower during TG than males; however, two recent larger studies reported no gender effect with TG. 9,19 An alternative reason for the differences between groups might be the motivation and competitiveness of the participants. Anecdotally, the football/grass group, who performed best across all conditions, consisted of associated club members who brought an element of competition to the testing arena (team practice). While this factor was difficult to minimise in the open environment where the testing took place it is unlikely to be present during screening of an injured/concussed athlete. It must also be noted that a possible limitation to the reliability of results exists due the use of a manual stopwatch. 5. Conclusion The neurological assessment of sports concussion with standardised motor performance tests is common; therefore it is vital that the effect of the footwear and sporting surface on these tests is understood. This study investigated the effect of footwear and sporting surface on the timed TG task, a dynamic measure of speed, coordination and balance. The results demonstrated that the time for a defined TG task depends on whether footwear is being worn and we propose that sporting surface and motivation might also be factors in performance outcome. In addition, there were relatively large variations in task performance within conditions. Therefore it is recommended that baseline assessment and subsequent screening of dynamic motor tasks are performed with the same footwear and, if possible, in the same environment for each sports participant. Practical implications Tandem Gait, as a timed dynamic task, is a practical and reliable measure of motor performance for use in concussion assessment tools. Timed performance of the Tandem Gait task varies depending on footwear, sports-surface and athletic group. Clinicians should standardise footwear when serial administration of the Tandem Gait task is required. Barefoot should be used as the default footwear condition in the Tandem Gait task during assessment for sportsrelated concussion. Acknowledgements The authors gratefully acknowledge David S. Jackson for assisting with manuscript preparation.

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