Postural Control in Karate Practitioners: Does Practice Make Perfect?

Journal Pre-proof Postural Control in Karate Practitioners: Does Practice Make Perfect? Amit Hadad, Natalie Ganz, Nathan Intrator, Neta Maimon, Lior Molcho, Jeffrey M. Hausdorff

PII:

S0966-6362(20)30060-6

DOI:

https://doi.org/10.1016/j.gaitpost.2020.01.030

Reference:

GAIPOS 7459

To appear in:

Gait & Posture

Received Date:

22 October 2019

Revised Date:

6 January 2020

Accepted Date:

31 January 2020

Please cite this article as: Hadad A, Ganz N, Intrator N, Maimon N, Molcho L, Hausdorff JM, Postural Control in Karate Practitioners: Does Practice Make Perfect?, Gait and amp; Posture (2020), doi: https://doi.org/10.1016/j.gaitpost.2020.01.030

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Postural Control in Karate Practitioners: Does Practice Make Perfect?

Amit Hadada, Natalie Ganza, Nathan Intratorb,c, Neta Maimond,e, Lior Molchod, Jeffrey M. Hausdorffa,c,f,g

Center for the Study of Movement, Cognition, and Mobility, Neurological Institute, Tel Aviv Sourasky Medical

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a

Center, Israel. b

Blavatnik School of Computer Science, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv

c

Sagol School of Neuroscience, Sackler School of Medicine, Tel Aviv University, Israel. Neurosteer Inc., Herzliya, Israel.

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d

e

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University, Israel.

The School of Psychological Sciences, Tel Aviv University, Israel.

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Department of Physical Therapy, Sackler School of Medicine, Tel Aviv University, Israel.

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Rush Alzheimer’s Disease Center and Department of Orthopaedic Surgery, Rush University Medical Center,

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Chicago.

*Corresponding author

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Prof. Jeffrey M. Hausdorff

Center for the Study of Movement, Cognition, and Mobility, Neurological Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. Phone: +972-3-6972587 Fax: +972-3-6947513/4 1

E-mail: [email protected]

Highlights Karate practice may lead to enhanced postural control.

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Previous studies of postural control in karate practitioners are inconsistent.

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Swimmers, athletes with similar health levels, and karate practitioners were studied.

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Under easy conditions, postural control was similar in both groups.

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Under challenging conditions, postural control was better in karate practitioners.

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Abstract

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Background: Karate training likely leads to enhanced postural control, however, previous studies did

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not always include a healthy, physically active comparison group and the findings are inconsistent. Research question: Will the postural control of experienced karate practitioners be better than that of experienced swimmers, i.e., athletes with similar characteristics who do not practice under conditions that require upright postural control? Methods: In this cross-sectional study, 20 experienced, male

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karate practitioners and 20 experienced, male swimmers, ages 20-50, performed four standing postural control tasks of increasing difficulty: (a) two-legged stance with eyes open; (b) one-legged stance with eyes open; (c) one-legged stance with eyes closed, and (d) a dual-task, one-legged stance with eyes closed and a verbal fluency challenge. The primary outcome measure was a functional, behavioral measure that reflects the loss of balance. Specifically, in tasks that included one-legged stance, every 2

touch of the raised foot to the floor was counted. Center-of-gravity movements were measured using a wearable sensor. Results: Task-related differences were seen in all of the postural control measures. In the OneLegEyesClosed task, the median number of touches was 0.00 in the karate group and 6.50 in the swimming group (p<0.001). In the OneLegEyesClosedWords task, the median number of touches was 0.00 in the karate group and 5.00 in the swimming group (p<0.001). Shannon entropy, a measure of the complexity of the sway of the center-of-gravity, was lower in the karate group (p=0.002), compared to the swimmers. Significance: Karate training is associated with a higher level of postural control, even when compared to a physically active age-matched comparison group. In addition to supporting the

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specificity of exercise training principle, these findings raise the intriguing possibility that karate may be useful as a form of pre-habilitation, potentially aiding in the prevention of age-associated declines in balance control.

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Key Words: Martial Arts, Postural Balance, Equilibrium, Floor Touches, Entropy, Exercise

Introduction

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The principle of specificity of exercise training [1-3] posits that specific balance-related exercises, such as repeatedly standing on one leg, are needed to achieve optimal postural control. This approach to

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exercise may, however, be boring and require extensive self-discipline and motivation to continue to practice it over extended time periods. Many people may prefer to maintain and improve their postural control as part of a wider leisurely or fun activity. Therefore, it is necessary to expand our understanding regarding which physical training and sports can improve postural control without having to repeatedly

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perform specific sets of exercises. In this study, we focused on karate as a potentially effective activity for improving postural control. Karate is based on two elements: Kumite focuses on dynamic postural control, and Kata focuses on dynamic and static postural control. Here we aimed to gain insight into the impact of karate on postural control. The connection between karate training and postural control has been evaluated in children [4,5], young adults [6-8], and adults aged 50 and over [9]. In most studies [4,6,7], postural control was assessed in 3

standing tasks, in particular, in one or two-legged stance with eyes open and closed, on a firm or foam surface. In some cases, the karate group was compared to a control group of physically active subjects [8,9], while in other cases, a comparison was made to subjects who are not physically active [4,6] and sometimes, an intervention was conducted [5]. Several reports support the hypothesis that karate training is related to improved postural control [4-6,911]. Indeed, one review [12] concluded that karate training contributes to enhanced postural control in healthy young adults. In contrast to these studies, Juras et al. reported that postural control was similar

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in the karate and control groups [7]. One possible explanation for these discrepancies is that the benefit of karate training may only be revealed during relatively demanding postural control tasks. Here we evaluated this possibility.

The purpose of the present study was to better understand the relationship between karate training and

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postural control. To this end, we included a control group of similar health and exercise history –

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experienced swimmers – to evaluate the specific role of karate training. We hypothesized that during relatively simple tasks, postural control would be similar in both groups due to a kind of floor effect. In

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addition, we hypothesized that during more complex and challenging tasks, the karate practitioners

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would show a higher level of postural control compared to the swimmers.

Materials and methods

Subjects

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20 experienced karate practitioners and 20 experienced swimmers were studied. After an initial search, we found it difficult to identify women karate practitioners and therefore, decided to recruit only men. Thus, male sex was an inclusion criteria. The other inclusion criteria were: (a) age 20-50 (inclusive); (b) absence of neurological disease like Parkinson's, multiple sclerosis, stroke, Alzheimer's, orthopedic disease or other disease likely to directly affect postural control; (c) currently exercising (swimming or karate) at least twice a week; (d) at least three years of experience practicing karate or swimming; (e) 4

lack of expertise in other types of postural control activities, e.g., slacklining, skateboarding, surfing; and (f) no other type of exercise training in the last two years. Subjects were excluded if they practiced or studied other martial arts or any other physical exercise that might have affected their postural control. All subjects provided informed written consent before participating in the study, as approved by a local Helsinki committee and by Tel Aviv University's ethics committee.

Tasks To assess postural control under different conditions, the subjects performed four standing tasks: (a)

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StandEyesOpen – two-legged stance with eyes open. In this task, the first metatarsal heads and the medial malleoli of both feet were in contact; (b) OneLegEyesOpen – one-legged stance with eyes open. In this task, the raised leg's hip was slightly flexed, the knee was extended, the ankle was in dorsiflexion,

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and the heel was approximately 5 cm above the ground; (c) OneLegEyesClosed – one-legged stance with eyes closed; (d) OneLegEyesClosedWords – a dual-task consists of the OneLegEyesClosed task

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and the simultaneous performance of a cognitive task, i.e., a verbal fluency challenge. In this challenge, the subject had 60 seconds to produce as many words as possible starting with a given letter (without

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repeating words or similar words, e.g., zebras and zebra would be counted only once). All subjects were given the same letter. In the one-legged tasks, we allowed the subjects to choose which leg to stand on

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to encourage optimal performance.

Procedures, Measures and Instruments

The subjects were assessed during one session that lasted approximately two hours. Because muscle

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fatigue may affect postural control [13], the testing did not take place after karate or swimming. Testing took place in a closed space, free from distractions on a floor (and not a mattress) while barefoot. The room temperature was approximately 24º Celsius. Subjects who usually wore prescription glasses or contact lenses, performed the tasks while wearing them. Testing of each subject was conducted as follows: (a) explanation of the research and its general objectives; (b) informed written consent; (c) characterization via a screening questionnaire and the 5

International Physical Activity Questionnaire – Short Form (IPAQ-SF) [14], Montreal Cognitive Assessment (MoCA) [15], Color Trails Test (CTT1 and CTT2) [16,17], Waterloo Handedness Questionnaire-Revised (WHQ-R) [18], Waterloo Footedness Questionnaire-Revised (WFQ-R) [18] and Mini-Balance Evaluation Systems Test (Mini-BESTest) [19]; (d) placing a DynaPort inertial measurement unit on the lower back (at L5-S1); (e) explanation of the tasks; (f) performing the tasks. Each task lasted for 60 seconds, with a 60-second rest break between each task-pair. We extracted six measures of postural sway from the lower-back sensor: three that reflect the magnitude

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of the movement of the center-of-gravity and three that reflect movement complexity. Since complexity measures can provide information that differs from and augments those based on magnitude [20], the inclusion of both types could lead to a more complete representation of sway. The three magnitude measures used were acceleration path [21], mean velocity [21] and root mean square [21,22]. The

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complexity measures were sample entropy [23], multiscale entropy [24] and Shannon entropy [25]. For

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more details see the supplementary material.

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Statistical Analyses

To compare the subject characteristics of the two groups, chi-square tests evaluated nominal variables, Mann-Whitney tests evaluated ordinal variables and scale variables that were not normally distributed,

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and independent samples t-tests evaluated scale variables that were normally distributed. To examine the main outcome measure, floor touches, non-parametric Wilcoxon tests evaluated task differences and Mann-Whitney tests evaluated group differences since the outcome was not normally distributed. To examine the six sway magnitude and sway complexity measures, we used multivariate analysis of

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variance (MANOVA). In cases of significant differences between the tasks, post hoc tests with a Bonferroni correction compared each task to the other. In cases of significant group differences, independent samples t-tests examined the group difference in each task separately. Statistical analyses were performed using SPSS version 20.

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Results

Subject Characteristics The 20 karate subjects came from seven different styles (i.e., Shitō-ryū, Gōjū-ryū, Shōtōkan, Shōrinryū, Kyokushin, Seido and Uechi-Ryū) and had 10 different trainers. Except for one subject, their routine training included both Kumite and Kata. Half of the karate subjects reported that they usually train on a mattress and half reported usually training on a floor. Among the karate practitioners, only two trained

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competitively. The others reported that they were training for personal development, physical fitness, and a healthy lifestyle and that they did not participate in competitions.

Unlike the karate practitioners, the swimmers did not report on a certain training style of swimming, except for one subject who reported training in a method called total immersion. The swimmers were

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trained by nine different coaches across the country. Half of the swimmers trained competitively. Most

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subject characteristics were similar in both groups (see Table 1); only side preference in the legs differed (p=0.046). Three swimmers had attention disorders creating a trend toward a group difference (p=0.072).

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The few diseases and conditions reported by subjects included exercise-induced asthma, colitis, and tennis elbow; these were not directly relevant to postural control.

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Floor touches

When analyzing floor touches among the tasks that included one-legged stance (see Table 2), there were significant differences between OneLegEyesOpen, on the one hand, and OneLegEyesClosed and OneLegEyesClosedWords, on the other hand (p<0.001). However, no significant difference was found

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between OneLegEyesClosed and OneLegEyesClosedWords (p=0.117). The number of floor touches was significantly different between the two groups during OneLegEyesClosed and OneLegEyesClosedWords (p<0.001) (see Figure 1) but not during the less challenging OneLegEyesOpen task (p=0.317). In the OneLegEyesClosed task, the median number of

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touches was 0.00 in the karate group and 6.50 in the swimming group. In the OneLegEyesClosedWords task, the median number of touches was 0.00 in the karate group and 5.00 in the swimmers. Due to the trend of a group difference in attention disorders, we examined the floor touch differences between the groups while leaving out the three swimmers with attention disorders. This did not change the results; significant group differences were observed during OneLegEyesClosed and OneLegEyesClosedWords (p<0.001), but not in the OneLegEyesOpen task (p=0.278), with the swimmers touching the floor much more often than the karate group.

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Among all the three tasks that included one-legged stance, the 20 swimmers touched the floor a total of 292 times while the 20 karate practitioners touched the floor a total of only 19 times (see Figure 1). This total number of floor touches in the three one-legged stance tasks was significantly different between

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the groups (p<0.001).

In each of the three tasks that included one-legged stance, the subjects chose which leg to stand on, i.e.,

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right or left. In this matter, we found that the support leg chosen was similar in the two groups (p>0.507). In addition, the number of support leg switches from task-to-task was also similar in the two groups

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Sway magnitude measures

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(p=0.157).

All three sway magnitude measures showed significant task differences (p<0.001) but no significant group differences (p>0.167) (see Table 3). There were also no interaction effects (p>0.293). In other words, the acceleration path, mean velocity, and root mean square were related to the level of task

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difficulty in both groups. In contrast, these measures were similar among the karate practitioners and the swimmers.

The acceleration path (p<0.001), the mean velocity (p<0.001), and the root mean square (p<0.001) showed significant task-related differences. Pairwise comparisons using Bonferroni corrections revealed that, in these measures, the averages of all the tasks differed significantly from each other (p<0.001) except for the more difficult tasks, OneLegEyesClosed and OneLegEyesClosedWords, which were 8

similar to each other (p>0.109). As expected, the values of the StandEyesOpen task were the lowest, the values

of

OneLegEyesOpen

were

higher,

and

the

values

of

OneLegEyesClosed

and

OneLegEyesClosedWords were the highest.

Sway complexity measures All the three sway complexity measures showed task differences (see Table 4). Some of them also showed either group differences or interaction effects. The sample entropy (p<0.001) and multiscale entropy (p<0.001) showed significant task differences. These measures did not show group effects

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(p>0.183), but they did show group × task interaction effects (p<0.004). In the case of task differences, pairwise comparisons using Bonferroni corrections revealed that the OneLegEyesClosed task was significantly lower than the other tasks (p<0.005). Unexpectedly, these measures were not related to the

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task level of difficulty.

Unlike the other complexity measures, the Shannon entropy measure showed significant task differences

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(p<0.001), significant group differences (p=0.002) and no interaction effect (p=0.319). Pairwise

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comparisons using Bonferroni corrections revealed that Shannon entropy during StandEyesOpen was significantly lower than the three one-legged stance tasks (p<0.001). Independent samples t-tests revealed that the two groups differed significantly from each other among all the tasks (p<0.046), except

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during OneLegEyesClosedWords (p=0.606).

When leaving out the three swimmers who had attention disorders, the Shannon entropy group differences remained significant (p=0.003). Specifically, the StandEyesOpen and OneLegEyesOpen tasks remained different among the groups (p<0.030), the OneLegEyesClosedWords task remained

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similar among the groups (p=0.605), and the OneLegEyesClosed task turned from significantly different (p=0.027) to a trend of difference (p=0.081) among the groups.

Discussion

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The present findings suggest that under some challenging conditions, young adult, healthy karate practitioners have a higher level of postural control than young adult, healthy swimmers. The higher levels of postural control of the karate practitioners were all seen during the eyes closed tasks (recall Figure 1). In other words, it seems that in relation to swimmers, karate practitioners are less dependent on vision to maintain postural control and that the advantage of karate practitioners may originate in the somatosensory system and/or the vestibular systems. Nonetheless, the fact that karate practitioners do not typically practice with closed eyes and still exhibit apparently better non-visual balance may suggest that karate training leads to improvements in postural control more generally, somewhat in contrast to

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the specificity of training principle [1-3]. These improvements are probably multifactorial and are not only based on the visual system.

Previous work associates karate training and higher levels of postural control [4-6,9-12]. However, to

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the best of our knowledge, this study is the first to present this link by counting the floor touches in tasks that include one-legged stance. The floor touch measure has some limitations, but it also sheds light on

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the subject from a new perspective and emphasizes the functional and behavioral aspects of postural

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control (as opposed to sway measures). The enormous group difference in the floor touch measure – a measure that reflects a loss of balance, along with the fact that in most of the sway measures there was no significant difference between the groups, indicates that there is not always overlap between the sway

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measures and performance-based measures of postural control. While the sway parameters are subject to interpretation, floor touches may more closely reflect everyday functioning. Drawing conclusions based solely on sway measures might not reflect the complete picture. This may be one of the reasons that some previous studies found that karate training is related to higher levels of postural control [4-

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6,9-11] and some did not [7]. Another possibility is that relatively easy and more challenging tasks were not always evaluated. The present findings suggest that the advantage of karate practitioners is only seen during relatively challenging postural control tasks. The Shannon entropy differences between the karate practitioners and swimmers are also of interest. The present results can be interpreted in light of a study in which 139 older adults were divided into two 10

groups, i.e., fallers and non-fallers, based on their history of falls [25]. The Shannon entropy values were lower in the non-fallers. This finding, together with our results, suggests that lower values of Shannon entropy of sway may reflect better postural control, parallel to the floor touch findings.

Limitations This study has several limitations. (a) Sample size – there were measures that showed consistent differences between groups among several tasks but these differences were not statistically significant (e.g., mean velocity, acceleration path). If the sample size was larger, these differences might have

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become statistically significant. Nonetheless, some group differences were already observed with the current sample size. (b) The order of the tasks was not random. This may have caused a learning effect and might have reduced the challenge of the tasks that were performed later. Still, since all subjects

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followed the same order, the impact of order is likely to be similar in both groups. (c) In tasks that included one-legged stance, the decision about which leg to stand on was left to the subjects.

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Retrospectively, we found that the support leg switching was similar in the two groups, a finding that minimizes the impact of this limitation. (d) In tasks that included one-legged stance, even though all

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subjects were instructed to avoid contact of the raised foot with the floor, no specific instructions were given to deal with the loss of balance. One subject could choose to "freeze" his center-of-gravity at the

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cost of more floor touches, while another could choose to leave his raised foot in the air at the cost of more movement of the center-of-gravity. In the future, it may be interesting to see if the groups use different strategies and how the strategy choice is related to postural control and exercise history. (e) The one-legged sway data were interrupted by the floor touches and these interruptions predominantly

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occurred in the swimmers, possibly leading to some of the group differences in complexity. (f) The cross-sectional nature of this study limits inferences regarding cause and effect. Still, since the subjects were well-matched with respect to most subject characteristics, the most likely interpretation is that the observed group differences were attributable to karate and swimming practice and not to some unknown confounders. Nonetheless, prospective studies, especially among older adults and others with deficits in postural control, would be informative. 11

Practical implications This study provides further evidence that karate training is associated with a higher level of postural control among young adults. This knowledge, along with other studies in different fields of exercise, can be used to create a "menu" of effective training options to improve postural control. Some people strive to maintain and even improve their balance and prefer to do so as part of a broader activity rather than by performing specific sets of exercise. For those people, the evidence that karate offers an advantage over activities that do not include standing and walking skills, such as swimming, might be

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important. More generally, these findings suggest that karate and perhaps other types of balance training may be useful as a form of pre-habilitation, possibly preventing age-associated declines in balance control [26,27]. Future longitudinal investigations in young and older adults are needed to address this

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intriguing possibility and its impact on falls, a major problem among many older adults.

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Conclusions

Although this study has limitations, the findings suggest that the postural control of healthy young adult

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swimmers and healthy young adult karate practitioners are fairly similar under relatively simple test conditions. Nonetheless, repeated practice of challenging balance tasks over many years in the karate

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practitioners apparently does lead to better postural control during relatively demanding tasks.

Conflict of interest statement

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Declarations of interest: none.

Funding

This work received no financial support.

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Acknowledgments We would like to express our gratitude to the research participants for their willingness to contribute their time and participate in the study and thank the swimming and karate coaches who helped with the

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recruitment of their students.

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Figure captions Figure 1: Group differences of floor touches in the tasks that included one-legged stance. There were significant group differences in OneLegEyesClosed and OneLegEyesClosedWords, but not in OneLegEyesOpen, with the

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karate group outperforming the swimmers in those conditions.

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Table 1: Subject characteristics of the two groups

Swimmers

p-

n=20

n=20

value

20 (100)

20 (100)

*

Age (years)

33.82 ± 08.00

35.40 ± 09.90

0.582

Height (cm)

175.80 ± 05.43

178.65 ± 05.45

0.106

Length of right leg (cm) †

90.48 ± 03.47

92.15 ± 03.90

0.159

Length of left leg (cm) †

90.58 ± 03.29

92.28 ± 04.20

0.163

Weight (kg)

76.90 ± 13.02

76.95 ± 06.65

0.988

Trainings per week (number)

03.00 [02-05]

02.00 [02-05]

0.512

Experience (years)

15.86 ± 10.73

15.20 ± 04.92

0.805

20 (100)

20 (100)

*

20 (100)

20 (100)

*

20 (100)

20 (100)

*

20 (100)

20 (100)

*

Yes

00 (00)

03 (15)

No

20 (100)

17 (85)

20 (100)

20 (100)

*

No postural disorders of lower limbs

20 (100)

20 (100)

*

No pain or limp while walking

20 (100)

20 (100)

*

Yes

01 (05)

02 (10)

No

19 (95)

18 (90)

Was not hospitalized in the last two months

20 (100)

20 (100)

*

No history of head trauma or brain surgeries

20 (100)

20 (100)

*

Positive

19 (95)

20 (100)

Negative

01 (05)

00 (00)

Yes

01 (05)

03 (15)

Sex: male

Lack of expertise in other types of

-p

postural control activities

ro of

Karate

No other activity in last two years

re

Hebrew is mother language

lP

No dyslexia

0.072

Diagnosed with attention disorders

ur na

Usually healthy

0.548

Jo

Diagnosed with any illness

0.311

General mood

Prescription medications

18

0.292

No

19 (95)

17 (85)

Yes

03 (15)

01 (05)

No

17 (85)

19 (95)

15.55 ± 03.39

15.05 ± 03.33

Physical

05 (25)

02 (10)

Office

11 (55)

11 (55)

Combined

04 (20)

07 (35)

Moderately physically active (IPAQ score)

02.00 [02-02]

02.00 [02-02]

1.000

Daily sitting (hours)

08.50 ± 04.13

07.93 ± 03.22

0.626

Unimpaired cognitive function (MoCA score)

29.00 [26-30]

29.00 [26-30]

0.506

Handedness (WHQ-R score)

48.50 [-24-65]

53.00 [-44-72]

0.167

Footedness (WFQ-R score)

04.50 [-06-13]

09.50 [-16-20]

0.046

Balance functions (MiniBESTest score)

28.00 [27-28]

27.00 [27-28]

0.209

CTT1 duration (seconds)

35.18 ± 15.48

28.45 ± 09.32

0.104

CTT2 duration (seconds)

61.58 ± 18.74

61.15 ± 19.75

0.944

32.70 ± 15.91

0.161

0.292

Physical pain

re

-p

Physical behavior at work

0.641

0.443

ro of

Education (years)

25.95 ± 13.88

lP

Time difference between CTT2 and CTT1 (seconds)

Note. Number (percent) is presented for nominal variables. Mean ± standard deviation is presented for scale variables. Median [minimum-maximum] is presented for ordinal variables and for scale variables which are not

ur na

normally distributed. CTT = Color Trails Test

* Constant values in all the subjects

Jo

† From the bottom of the heel to the greater trochanter

Table 2: Task differences of floor touches in all the subjects (n=40)

OneLegEyesOpen OneLegEyesClosed

19

OneLegEyesClosedWords

Floor 0.00 [0-1]

1.50 [0-44]*

0.00 [0-24]*

Touches

Note. Median [minimum-maximum] is presented for floor touches. There were significant differences between OneLegEyesOpen, on the one hand, and OneLegEyesClosed and OneLegEyesClosedWords, on the other hand. However, no significant difference was found between OneLegEyesClosed and OneLegEyesClosedWords (p=0.117).

Table 3: Group and task differences in the sway magnitude measures

ro of

*p<0.001 compared to OneLegEyesOpen

OneLeg

Stand

OneLeg

OneLeg

-p

EyesClosed

p-value

Task

Group

Diff.

Diff.

<0.001

0.416

<0.001

0.167

<0.001

0.597

EyesOpen EyesOpen EyesClosed

Words

1568.530

9204.649

8835.559

±

±

±

±

225.260

590.056

7352.662

7910.371

474.447

1837.744

6294.117

8052.798

±

±

±

±

104.376

1112.408

4800.489

6956.799

0.269

0.387

1.529

1.711

±

±

±

±

0.071

0.103

0.614

0.752

0.314

0.438

1.778

2.098

±

±

±

±

0.088

0.113

0.859

1.103

0.016

0.034

0.194

0.171

±

±

±

±

path (cm/sec2)

ur na

swimmers

karate

Mean

Jo

velocity

lP

Acceleration

re

karate

525.135

(cm/sec)

swimmers

karate

20

Root

0.004

0.010

0.131

0.129

mean

0.020

0.056

0.224

0.173

±

±

±

±

0.009

0.039

0.326

0.106

square

swimmers

(cm/sec2)

Note. Entries are means ± standard deviations.

ro of

Table 4: Group and task differences in the sway complexity measures

OneLeg

Stand

OneLeg

OneLeg

EyesOpen EyesOpen EyesClosed

EyesClosed

Task

Group

Words

Diff.

Diff.

<0.001

0.183

<0.001

0.497

<0.001

0.002

0.666

0.471

±

±

±

±

sample

0.134

0.075

0.106

0.104

entropy

0.602

0.556

0.528

0.533

±

±

±

±

karate

multiscale entropy

Jo

swimmers

Shannon

karate

entropy swimmers

re

lP

0.094

0.176

0.081

0.071

79.877

87.600

59.245

78.090

±

±

±

±

11.193

10.990

17.204

13.039

71.381

75.515

73.871

77.315

±

±

±

±

12.439

18.754

12.575

13.030

3.210

4.154

4.309

4.649

±

±

±

±

1.048

0.511

0.471

0.548

3.907

4.628

4.694

4.752

ur na

swimmers

0.575

-p

0.634 karate

p-value

21

±

±

±

±

1.089

0.660

0.582

0.695

Note. Entries are means ± standard deviations. When leaving out the three swimmers who were diagnosed with attention disorders, the Shannon entropy group

Jo

ur na

lP

re

-p

ro of

differences remained significant (p=0.003).

22