An external focus of attention attenuates balance impairment in patients with Parkinson's disease who have a fall history
Introduction
Parkinson's disease is a progressive neurodegenerative disease that characteristically produces a variety of motor control problems and movement disorders including bradykinesia, rigidity, resting tremor, and deterioration in balance and postural control. The cumulative effects of these impairments often result in considerable disability, thereby predisposing the individual to falling. Whereas associated motor deficits are not usually directly life threatening, they can contribute to falling, which in turn can lead to severe injuries (e.g. head injuries, fractures, etc.). These injuries may ultimately lead to hospitalisation and/or confinement to a wheelchair. Falling can also lead to fearfulness about walking, which may result in social isolation.
Koller et al. [1] reported that 10% of patients with Parkinson's disease fall more than once per week. In addition, patients are five times more likely to suffer fall-related fractures [2]. Johnell et al. [2] reported that by 10 years after diagnosis, an estimated 27% of a Parkinsonism cohort had experienced a new hip fracture, which was a 20-fold increase in risk compared with an age- and sex-matched control group. Clearly, such statistics highlight that a primary focus in physiotherapy intervention of patients with Parkinson's disease is the prevention of falls [3]. Interestingly, postural instability, which is implicated as a causative factor of falls in this group, is the only major motor sign that appears to be resistant to dopaminergic therapy [1]. This further illustrates the need for developing physiotherapy interventions that effectively enhance balance in those with Parkinson's disease.
One potential way to improve physiotherapy balance training in Parkinson's disease comes from motor learning research, which suggests that performance on a variety of motor skills, such as balance, can be enhanced in young, healthy adults by giving them attentional focus instructions [4], [5], [6], [7], [8], [9], [10], [11], [12]. Specifically, it has been demonstrated that directing the performer's attention to the effects that his or her movements have on the environment (external focus) is more effective than directing attention to the movements themselves (internal focus). For example, using a balance task, Wulf et al. [5] compared the effectiveness of instructions that directed the performers’ attention to their feet (internal focus) with those of instructions that directed attention to markers on the balance platform (external focus). Compared with an internal focus, the adoption of an external focus resulted in enhanced balance learning. It has also been shown that the focus of attention adopted on a suprapostural task (e.g. pointing) can affect postural control, with an external focus resulting in greater postural stability than an internal focus [13]. Taken together, these results suggest that external focus instructions can enhance the learning of balance tasks in subjects without pathology. If these results could be replicated in subjects with Parkinson's disease, this could lead to more effective physiotherapy intervention directed at improving balance.
Importantly, external focus advantages have also been found in comparison to control conditions without attentional focus instructions [5], [14], [15]. That is, while internal focus and control groups often show similar performances, an external focus generally results in enhanced performance and learning. This seems to hold true for the learning of new skills [5], [14], as well as for the performance of well-practiced skills (e.g. standing still) [13]. This finding is important as it suggests that if subjects are given external focus instructions, motor performance can be enhanced above and beyond their normal level of performance. This might, therefore, have important implications for training procedures used in physiotherapy settings.
Wulf et al. [7], [8], [10], [16] proposed a ‘constrained action hypothesis’ to account for these external focus benefits. According to this view, subjects focusing on their body movements tend to actively intervene in the control of their movements, which interferes with automatic motor control processes. In contrast, focusing attention on the movement effect (i.e. the outcome of the movement) allows unconscious processes to control the movements required to achieve this effect. That is, an external focus promotes the utilisation of automatic control processes, resulting in enhanced performance and learning. In fact, the benefits of an external focus appear to increase with task complexity [17], [18]. If the task is relatively simple and already controlled relatively automatically, an external focus might not provide additional advantages. However, if the task is relatively complex and challenging for the individual, an external focus typically results in enhanced performance.
Section snippets
Aim of the study
The purpose of this study was to explore the generalisability of the attentional focus advantages outlined by Wulf and co-workers [4], [5], [6], [7], [8], [9], [10], [11], [12] in a population of subjects with Parkinson's disease. Specifically, we wanted to determine whether balance in subjects with Parkinson's disease could be improved by giving them external focus instructions, relative to internal focus or no attentional focus instructions (control condition). In addition and perhaps most
Subjects
A convenience sample using disproportional stratified sampling (1:1 ratio of faller to non-faller) of 22 subjects (five females, 17 males) was recruited from the local American Parkinson's Disease Association. Diagnosis of idiopathic Parkinson's disease was made by a neurologist. Subjects were all Hoehn and Yahr Stage II or III [19], and were aged 61–86 years (mean age: 72.7 years, mean onset: 6.7 years). Ten of the 22 subjects reported at least one unexplained fall within the last year (mean:
Fallers and non-fallers
Equilibrium scores There was a main effect of condition (F [2, 42] = 41.30, P < 0.001, Eta2 = 0.66) indicating increasingly lower equilibrium scores with increasing task difficulty (eyes open, eyes closed, sway referenced/eyes open). The main effect of attentional focus was not significant (F [2, 42] = 2.22, P > 0.05), but the interaction of condition and attentional focus was significant (F [4, 84] = 2.86, P < 0.05, Eta2 = 0.12) Follow-up ANOVAs and post hoc tests (LSD) revealed that the only significant
Discussion
The present study examined the influence of different types of attentional strategies for balance in subjects with idiopathic Parkinson's disease. Specifically, we wanted to examine whether previously found benefits of adopting an external focus of attention would be observed for this population. While there were no significant external focus advantages for the combined group of subjects (with and without a history of falls), benefits of an external focus emerged for the fallers under
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2021, Human Movement ScienceThe autonomy and focus of attention strategies under distraction: Frequency and sample entropy analyses in a dynamic balance task
2021, Human Movement ScienceCitation Excerpt :Following research replicated the benefits of external focus in both dynamic (Abdollahipour, Land, Cereser, & Chiviacowsky, 2019; Bahmani, Diekfuss, & Kharestani, 2019 in Exp. 1; Chiviacowsky, Wulf, & Wally, 2010; McNevin, Shea, & Wulf, 2003; Wulf et al., 1998, Wulf, McNevin, & Shea, 2001) and static balance tasks (Landers, Wulf, Wallmann, & Gaudagnoli, 2005; Rhea, Diekfuss, Fairbrother, & Raisbeck, 2019). A meta-analysis confirmed the external focus benefits for maintaining postural control (Kim, Jimenez-Daiz, & Chen, 2017).
The effect of attentional focus on movement accuracy in an immersive and interactive virtual reality environment
2021, Neuroscience LettersCitation Excerpt :A subtle difference in verbal cues shifts individuals' attentional focus (AF) [1,2] and affects motor performance and learning [3]. While various categories of AF have been examined, directing attention to the effects of the movement on the environment (EXF) is robustly beneficial to motor behavior when compared to attention directed to body parts or body movements (INF) [1,2,4–9]. According to the constrained-action hypothesis [10,11], an INF disrupts the motor system, whereas an EXF enhances performance by promoting greater automaticity throughout the motor system [10,11].
Attention focus modulates afferent input to motor cortex during skilled action
2020, Human Movement ScienceCitation Excerpt :The benefits of an external focus have been demonstrated across a litany of upper (Lohse, Sherwood, & Healy, 2010; Wulf, Gartner, McConnel, & Schwarz, 2002; Wulf & Su, 2007; Zachry, Wulf, Mercer, & Bezodis, 2005) and lower limb (Wulf et al., 2002; Wulf, Hoss, & Prinz, 1998) motor skills as well as postural control (McNevin, Shea, & Wulf, 2003; McNevin & Wulf, 2002; Rhea, Diekfuss, Fairbrother, & Raisbeck, 2019; Wulf et al., 1998) in healthy populations. The external focus also appears to benefit use-dependent learning paradigms in clinical populations (Chiviacowsky, Wulf, & Wally, 2010; Landers, Wulf, Wallmann, & Guadagnoli, 2005). The behavioral benefits of adopting an external focus have been associated with enhanced dynamic and kinematic efficiency as well as reduced energetic costs (Lohse et al., 2010; Lohse & Sherwood, 2012; Schucker, Hagemann, Strauss, & Volker, 2009; Vance, Wulf, Tollner, McNevin, & Mercer, 2004; Zachry et al., 2005).