# The Effects of Functional Ankle Taping on Postural Stability in Elite Judo Players
## 4 Discussion  
The purpose of the current study was to biomechanically examine the effects of functional ankle taping on postural stability in elite Judo players. Particularly, this study used both linear (i.e., COPSWAY and COPVEL) and nonlinear biomechanical postural measures, providing a holistic perspective on how the functional taping intervention influences Judo players' postural stability. First, with regard to the linear measures of postural stability, lower COPSWAY and COPVEL values were observed in a narrow stance with a taping condition than non-taping condition. This indicates that ankle taping could limit joint movement, which may in turn increase the ankle joint stiffness. Perhaps, enhanced joint stiffness could strongly support ankle joint, making COP movement smaller while affecting COP's range in a narrow stance. In other words, this result supports previous research suggesting that ankle taping is effective in enhancing ankle stability by strengthening ankle muscles involved in the ankle movement [2,24]. On the contrary, there were no differences in COPSWAY and COPVEL between taping and non-taping conditions during normal and wide stance standing tasks. Given that the main performance of Judo is to maintain postural stability with wide stance standing [8], our finding suggests that the ankle taping may not be beneficial for improving performance of Judo players. Rather, the ankle taping could suppress the ankle joint movement in a narrow stance, showing lower COPSWAY and COPVEL. This finding may reflect a reduced degree of freedom or flexibility representing an adaptability in various conditions to fluidly control dynamic movements. In other words, it is difficult to explain whether a small or a large value in linear postural measures is good or bad when evaluating the effect of ankle taping on postural stability. Hence, this plausible explanation suggests that only using linear methods of COPSWAY and COPVEL to assess the effectiveness of taping and postural stability may be limited. This is because the definitive value of linear postural measures may not be sufficient to explain postural stability over a certain period of time [25]. Furthermore, we additionally assessed dynamic postural stability of Judo players through a nonlinear method (Approximate Entropy, ApEn). Results indicated that ApEn values in anteroposterior (ApEnAP) were smaller in the overall standing task when ankle taping was applied compared to a non-taping condition. In normal and wide stances, particularly, lower ApEn values were observed in taping compared to non-taping. As previously mentioned, it might be possible that the ankle taping increased ankle stiffness and reduced the degree of freedom of the ankle joint movements. Indeed, observed lower \begin{table}
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* Significant difference (\(p<0.05\)) between taping and non-taping. Abbreviation: COPSWAY, 95% Confidence Ellipse sway; COPVEL, COP velocity; ApEnAP, Approximate Entropy Anteroposterior; ApEnML, Approximate Entropy Mediolateral.  
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Table 1: Mean, standard deviation and p-value from paired \(t\)-tests for all dependent variables including COPSWAY, COPVEL, ApEnAP and ApEnML. \(p<0.05\) for difference between taping and non-taping conditions. ApEn values in most stance standings may reflect that taping had an adverse effect on flexibility that is necessary for balance control in various dynamic postural conditions [2]. The implication of this nonlinear finding is that reduced ankle flexibility due to taping can have an adverse effect on Judo players who need to adeptly change postures and control those changed postures. In other words, postural complexity is important in fluidly adapting to changing situations. Specifically, the less the postural complexity, the less the flexibility and the greater the consistency in posture control [26]. In summary, taping can negatively affect flexibility that creates COP during fast or slow dynamic movements.