To the best of our knowledge, this study is the first to investigate the effects of ankle brace application pressures on postural control and electromyographic activation sequence of lower limb muscles. In a recent study, Papadopoulos et al. [
26], examined the effects of different ankle brace application pressures on the peroneus longus reaction time, during a sudden inversion stress test and found that ankle brace application with medium and high pressure, resulted in a significant delay of the peroneal reaction time. In the current study, we investigated the effect of no brace application and two different ankle brace application pressures, on single limb balance control and the electromyographic activation sequence of four lower limb muscles. The results showed that overall with the specific type of brace that was used in this study, postural control, as assessed by the total stability parameter '
σ
r', was not positively or adversely affected by the two different brace application pressures. This finding is in agreement with previous studies, which showed that ankle bracing had no effect on postural control, without however, referring to the pressure of brace application [
5,
6]. It was also shown that different ankle brace application pressures had no effect on the mediolateral plane but on the other hand, it significantly deteriorated balance in the anteroposterior plane. These findings are partly in agreement with Bennell & Goldie [
1], and Papadopoulos et al. [
2], who also found that ankle bracing adversely affected balance in young healthy volunteers. However, the fact that mediolateral balance was not affected in any of the three brace application conditions may be more valid in this research since in this study sample, the COP trajectory during single limb balance, mainly traveled in the mediolateral direction. The deterioration of balance in the anteroposterior direction may also be attributed to the fact that muscular control of single limb balance which is more efficient in the AP direction [
27], was adversely affected by the application of the ankle brace. Furthermore, since both the mediolateral (
σ
Apr) and the anteroposterior (
σ
Latr) stability parameters, as well as the total stability parameter (
σ
r), were not significantly affected, it may be concluded that overall, the application of the two different ankle brace application pressures, had no positive or negative effect on quiet single limb balance. This is also supported by Riley et al. [
7], who stated that the stability parameter they calculated, which combines both the centre of pressure excursion and centre of pressure excursion velocity, as well as the mediolateral and anteroposterior planes, is more valid and representative for the assessment of standing balance than separately assessing each of these parameters alone. This information may be useful in future studies as well as in the clinical setting, since it seems that the application of the laced-up ankle brace with a moderate and a high pressure, had no significant stimulation effect on the peripheral, mainly skin receptors, and therefore afferent signals were not strong enough to provoke a specific central response and affect single limb balance control. Another finding of this study was that single limb balance was significantly worse with closed eyes as compared to open eyes. This is in agreement with previous studies [
2,
28‐
31] and further establishes the importance of vision which is one of the three major sources of balance control together with the vestibular system and the peripheral joint receptors [
32].
The results of the electromyographic measurements showed that the sequence of lower limb muscle activation onset was not altered by the application of two different ankle brace application pressures. This finding cannot be compared with previous studies since this is the only study that has investigated the effect of ankle bracing on the EMG activity of lower limb muscles and, as mentioned above, the only that has examined the effect of different brace application pressures. However, useful information that arises is that different ankle brace application pressures do not change the ankle strategy of balance control, which is the one that dominates during balance of young healthy subjects [
15,
10,
14,
9,
33]. Therefore, the fact that the more distal peroneus longus and gastrocnemius muscles were activated faster than the more proximal thigh muscles (rectus femoris and biceps femoris), both in the condition without brace and the conditions with moderate and high brace application pressures, further supports the hypothesis that the central nervous system (CNS) does not alter its single limb balance control strategy. Several explanations may be given for this observation: first, the skin receptors are either not adequately stimulated by the high application pressure of the brace so as, in turn, to provoke a CNS response, or their role in controlling single limb balance is less important. Second, the fact that the study sample consisted of non-injured subjects, may in part explain the lack of pressure application effect on balance. It could be argued that joint receptors in healthy subjects may be adequate in preventing single balance distortion with different ankle brace application pressures. However, this is not supported by previous studies since ligament receptors are stimulated in the end ranges of joint motion and therefore ligament injury affects only the mechanical and not the functional dynamic stability of the joint which is mostly controlled by the muscle spindles [
32]. Further research, which will investigate the effect of ankle brace application in injured subjects too, is necessary.