Original researchMen with unilateral Achilles tendinopathy have impaired balance on the symptomatic side
Introduction
Achilles tendinopathy (AT) is characterised by activity related pain localised to the Achilles tendon, which can affect both daily activities and sporting performance.1 People with painful Achilles tendons often have intratendinous pathology, but asymptomatic pathology is also common, demonstrating an unclear relationship between structural pathology and pain.2 The prevalence rate of AT in runners is reported as 6.2–9.5%, and as high as 18.5% in an ultra-marathon running population.3
Motor deficits including reduced plantarflexion torque have been reported in people with, and preceding the onset of, Achilles tendon pain.4, 5 However, the mechanism behind this impaired motor function in people with Achilles tendon pain is not clear. In patellar tendinopathy, Rio et al.2 recently reported an increase in both motor cortex inhibition and corticospinal excitability of the rectus femoris muscle, providing some insight into potential explanations for impaired motor function in lower limb tendinopathy. Furthermore, two recent studies found reduced proprioceptive function (i.e. decreased movement and load sensing ability) associated with patellar tendinopathy.6, 7 This impaired motor control during functional loading tasks in lower limb tendinopathy may alter tendon loading, and subsequently result in pain development and persistence.2
Single leg standing balance is a potential motor deficit that has received very little attention in lower limb tendinopathy. The advantage of single leg standing balance compared to other measures of motor performance in the literature (e.g. proprioceptive measures such as joint position sense or threshold to detection of a passive movement) is that it is easily and quickly measured in clinical practice. Standing balance requires a coordinated motor output that involves the integration of feedforward motor prediction, as well as feedback proprioceptive input.8 Proprioceptive information about force, effort and balance are provided principally by mechanoreceptors in the skin, muscle spindle and the intra-tendinous golgi tendon organ (GTO).9 It is possible that pathological changes to tendon structure with lower limb tendinopathy, including the Achilles, may impact on GTO function and proprioception, resulting in impaired sensorimotor control during single leg standing balance. Identification of potential motor deficits, such as impaired standing balance in tendinopathy, may help to monitor the effect of current interventions on motor output.
The aim of this study was to investigate single leg standing balance by assessing COP path length in males with unilateral AT. We hypothesised that participants would have reduced single leg standing balance on their affected side compared with the unaffected side.
Section snippets
Materials and methods
Males with midportion AT were recruited from two sports medicine clinics in Melbourne, Australia. Given differences in standing balance between genders is unknown in AT, we only recruited men to ensure homogeneity. Inclusion criteria were similar to prior studies (e.g. Munteanu et al., 2014) and included; age 20–60 years old, fluent in written and spoken English, able to provide informed written consent, and current clinical diagnosis of midportion Achilles for >12 weeks as determined by the
Results
Comparisons for outcome measures are provided in Table 2. 14/21 (67%) of symptomatic limbs were the non-dominant leg. AP diameter of the tendon was significantly higher on the symptomatic side. A high proportion of tendons on the asymptomatic side (43%) showed pathology on ultrasound. COP path length was greater on the symptomatic side during single legged stance with eyes closed (p = 0.001), but not open.
The only significant correlations were between COP path length and AP diameter during the
Discussion
This is the first study to assess single leg standing balance in patients with AT. Impaired balance (sway amplitude) during single legged stance with eyes closed on the symptomatic side indicates a sensorimotor deficit among people who have Achilles pain and pathology. Single leg standing may be a simple clinical test that could identify motor control deficits between people with and without AT. These findings may also have implications for AT management, but further work is needed first to
Conclusion
Patients with symptomatic AT demonstrate a unilateral deficit in eyes closed single leg standing balance when compared with their contralateral limb. Sensory dysfunction may contribute to altered sensorimotor output, and the relative influence of impaired ascending afferent information and descending motor control mechanisms requires further investigation. The observed changes to motor output during the single leg standing task may be influenced by cognitive emotional factors, and other “top
Practical implications
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People with AT displayed deficits in single leg standing with eyes closed on the symptomatic but not asymptomatic side.
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Single leg standing with eyes closed is a simple clinical test that may be useful to identify standing balance deficits among people with AT.
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Single leg standing with eyes closed may be useful to monitor the effect of traditional rehabilitation interventions on motor control.
Acknowledgements
Adam Bryant is a recipient of an NHMRC Career Development Fellowship (R.D.Wright Biomedical, #1053521). Ross Clark is a recipient of an NHMRC Career Development Fellowship (R.D.Wright Biomedical, # 1090415). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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2023, Clinical BiomechanicsCitation Excerpt :Input from the visual system provides information about relative body position to the surrounding environment; the lack of visual information contributes to instability (Faquin et al., 2018). Scholes et al. (2018) investigated men with unilateral Achilles tendinopathy and demonstrated impaired balance on the symptomatic side during single-leg standing with eyes closed but not during single-leg standing with eyes open. They concluded that structural changes within the affected tendon might impair proprioception.
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2018, Drug and Alcohol DependenceCitation Excerpt :However, these sway variables are not commonly used to assess sway and appear to have been used in only one previous study by this same group (Thewlis et al., 2014). By contrast, COP path length is routinely used to assess postural sway, with numerous published studies employing this measure to quantify sway in just the last calendar year (Clark et al., 2017; Howard et al., 2017; Kalron, 2017; Koyama and Yamauchi, 2017; Lee and Brown, 2017; Ludwig, 2017; Pavao et al., 2017; Schmidt et al., 2017; Scholes et al., 2017). The idea of 2-component COP was introduced in the 1990s and the rambling-trembling method (Zatsiorsky and Duarte, 1999) in particular has garnered substantial empirical support.
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