Effects of fatiguing treadmill running on sensorimotor control in athletes with and without functional ankle instability
Introduction
Ankle sprains are among the most common sports injuries, with a general incidence reported as high as 4.2 per 1000 person-hour in team sports (Fong et al., 2007). About 40% to 70% of individuals develop long term impairments following an ankle sprain, including loss of ankle function, hypo- or hypermobility, pain, weakness or swelling (Anandacoomarasamy and Barnsley, 2005, Löfvenberg et al., 1994, Verhagen et al., 1995, Wikstrom et al., 2009). This condition is referred to as chronic ankle instability and may originate from mechanical and functional ankle instability (FAI) (Hertel, 2002).
FAI is operationally defined as experiencing repeated episodes of ankle instability and spraining subsequent to an initial sprain and has been attributed to alterations in the sensorimotor control system. Data from recent meta-analyses suggest that deficits in proprioception (McKeon and McKeon, 2012), evertor muscle strength (Arnold et al., 2009) as well as postural control (Munn et al., 2010, Wikstrom et al., 2010b) exist in individuals with FAI. These impairments might explain frequent episodes of instability and the high risk of recurrent sprains in this population (Hertel, 2002). Investigating athletes who successfully return to preinjury levels of sports activity while having no injury recurrences or feelings of instability (copers) may help to elucidate the role of the sensorimotor system in the development of FAI (Hertel and Kaminsky, 2005).
Sensorimotor control is also temporarily impaired in physically fatigued state. Increased muscle reaction time (Benesch et al., 2000), reduced muscular activation (Thorlund et al., 2008), altered proprioception (Mohammadi and Roozdar, 2010), and postural control (Paillard, 2012, Zech et al., 2012) in healthy, non-injured individuals following fatiguing exercise were reported in the literature. Thus, it is suggested that dynamic joint stability is decreased in the fatigued state (Hiemstra et al., 2001), potentially leading to a higher risk of sustaining an ankle sprain. This is supported by epidemiological studies from team ball sports showing an increased incidence of traumatic injuries towards the end of a game (Ekstrand et al., 2011, Gabbett, 2000).
The deleterious effects of physical fatigue on sensorimotor control are well investigated in healthy, non-impaired individuals. However, athletes with existing sensorimotor impairments, such as FAI individuals, might respond differently to physical fatigue. Preliminary evidence indicates that athletes with FAI (Gribble et al., 2004, Gribble et al., 2007) and copers (Steib et al., 2013) suffer larger fatigue-induced impairments of dynamic postural control as compared to non-injured controls. This is an important issue as poor postural control is associated with an increased risk of ankle injury (McGuine et al., 2000, Noronha et al., 2012, Plisky et al., 2006). However, existing evidence is limited and to date no study has compared fatigue effects between copers and individuals with FAI.
Thus, the primary aim of this study was to compare the effects of fatiguing exercise on dynamic postural control, as measured by the star excursion balance test (SEBT), in individuals with FAI, ankle sprain copers, and non-injured athletes. Additionally, static postural control, jump landing stabilization times, and proprioception were assessed to evaluate effects on different levels of the sensorimotor control system. We hypothesized that dynamic postural control would be more substantially impaired (decreased SEBT performance) by fatigue in previously injured athletes and that individuals with FAI would be most severely affected.
Section snippets
Participants' characteristics
In this cohort study, a convenience sample of 57 athletes between 18 and 35 years was recruited from the university sports program and local ball sports teams (handball, volleyball, basketball, soccer). Participants exercised at least three times per week for a minimum of 30 min per session. All participants gave written informed consent, and local ethics committee approval was obtained.
Results
We included 19 individuals with FAI, 19 ankle sprain copers and 19 non-injured controls. There were no significant differences in demographic data between groups (Table 1). The FAI group had significantly more ankle sprains (P = .018) and giving-way episodes (P = .000) compared to copers. Further, the FAI group had significantly (P = .000) lower scores in the FAAM compared to copers (Table 1). No adverse events were reported during the fatiguing running. Mean RPE at exhaustion was 19.5 (0.6) and mean
Discussion
The primary aim of this study was to compare the acute effects of physical fatigue on dynamic postural control between athletes with FAI, ankle sprain copers and non-injured individuals. Dynamic postural control, as assessed by maximum SEBT reach distances and single leg jump stabilization times, was negatively affected in the fatigued state. Further, postural sway velocity in single leg stance was increased. No fatigue effects were seen on passive joint position sense. Contrary to our
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