Ankle sprain occurs commonly among athletes in sports (Hootman et al., 2007; Mack et al., 1982; van den Bekerom et al., 2012). An ankle sprain accounts for 14.8% of all injuries in collegiate sports, and the athletes who participate in activities that involves jumping and landing, such as basketball and volleyball, have a higher chance of ankle sprain (Hootman et al., 2007). Pain, decreased range of motion, and functional instability occur as a result of ankle sprains (Ivins et al., 2006). Yeung et al. (1994) reported that 30.2% of patients experience pain.
Ankle sprains recur at a high rate (56-74%) (McKay et al., 2001), and repeated ankle sprain leads to chronic ankle instability. Because chronic ankle instability incurs enormous economic and social costs, preventing lateral ankle sprain recurrence is important.
Ankle braces are used as one of the preventive measures against ankle sprains. The benefit of the ankle brace includes: 1) decreasing anterior tibial shear force; 2) decreasing range of motion in ankle and subtalar joints; 3) improving ankle proprioception facilitated by mechanoreceptors; and 4) maintaining dynamic balance ability (Hardy et al., 2008). An ideal ankle brace should protect the ankle from lateral ligament injury without restraining its normal movement.
There are various ankle braces, including soft braces, semi-rigid braces, and rigid braces. The braces are prescribed widely to prevent sports injuries during athletic practice or competitions and treat them if they do sustain an injury. Sitler et al. (1994) reported that use of a semirigid brace (SRB) could significantly reduce the frequency of ankle injuries. Clinically, SRBs are believed to help athletes with functional ankle instability by improving neuromuscular control and mechanical stability. The ability of ankle braces to prevent ankle sprain, however, is still debatable (McGuine et al., 2012).
Although a number of studies have investigated the effect of ankle braces on postural control, evidence on the effects of ankle braces on postural control is still inconclusive. Guskiewicz and Perrin (1996) and Baier and Hopf (1998) reported the positive effects of ankle braces on postural control. To the best of our knowledge, however, there have been no comparisons of the effects of soft braces (SB) and SRBs on static or dynamic postural control after landing.
Dynamic postural control can be assessed using the Dynamic Postural Stability Index (DPSI) (Wikstrom et al., 2006). The DPSI assesses balance while the subject transits from a dynamic to static state in single-leg hop stabilization maneuver. Thus it is a functional measurement of neuromuscular control (Wikstrom et al., 2006).
The effects of the SB, SRB, and no brace (NB) on static and dynamic balance could have implications for athletes, trainers, and rehabilitation staff. The difference in the effects of SRB and SB on static and dynamic postural control after landing is not known. The purpose of this study was to compare the effects of SBs and SRBs on static and dynamic postural control. We hypothesized that there are no difference between interventions in static postural sway and dynamic postural stability.
A total of 21 healthy, young, recreationally active men [age 24.0 [+ or -] 3.6 years (mean [+ or -] SD); height 1.74 [+ or -] 0.06 m; body weight 63.1 [+ or -] 14.4 kg] voluntarily participated in this study. "Recreationally active" was defined as having participated in at least one exercise session per week during the preceding 2 months but no involvement in structured exercise training during this period (Costa et al., 2009). Exclusion criteria of this study were: 1) current ligamentous defects; 2) history of a grade II or higher sprain; 3) history of ligament or joint reconstruction or repair; 4) trauma (including fracture, myositis ossificans, burns); or 5) dysfunction of the vestibular system affecting balance. All the participants never used any of the braces used in this study. The power for each analysis of variance (ANOVA) was not less than 0.65 for an effect size more than 0.8 (Cohen et al., 1998). The Ethics Committee of the Graduate School of Health Sciences, Hiroshima University approved the study protocol (ID number, 1411).
Subjects were assigned to three randomly ordered experimental conditions (NB, SB, SRB). Their order experimental conditions were counterbalanced across subjects. The participants performed under three brace conditions (SB, SRB, NB) in various orders on three separate days, with an intersession interval of at least 24 h and no more than 48 h between tests. Braces were fitted to each subject by a single investigator in order to minimize within-subject and between-subject variations.
Zamst ankle braces (Nippon Sigmax Devices, Inc., Tokyo, Japan) were used in this study. The SB (Zamst FA-1) was a nylon supporter and was designed with two layers of support for weak and swollen ankles while allowing dorsiflexion/plantar flexion (Figure 1). An inner wrap adjusts with a hook-and-loop closure to provide compression and control of the ankle and heel area. The SRB (Zamst A1) was a nylon supporter and included L-strap and Y-strap stabilizers. It is designed to resist inversion loads while allowing dorsiflexion/plantar flexion and stabilize the ankle joint (Figure 2). Braces were fitted to each subject by a single investigator in order to minimize within-subject and between-subject variations.
To compare the effect of each condition, we...