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PHYS THER
Vol. 89, No. 2, February 2009, pp. 170-172
DOI: 10.2522/ptj.20080045.ar
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Research Reports

Author Response

Gabriele Wulf, Rebecca Lewthwaite, Merrill Landers and Thomas Töllner


We thank Morris for her thoughtful commentary1 on our study.2 We concur with her in the observation that our study provides further support for the role that instructional sets or pretask instructions can play in enhancing the motor performance of individuals with Parkinson disease (PD).3,4 Given the constellation of cognitive and movement symptoms common in people with PD, as well as the relationship of cognitive processes to movement control,5 it is important to recognize that many individuals with PD retain their capabilities to distinguish between differing instructions and to act upon those distinctions motorically (eg, to increase stride length upon request). Our study provides additional evidence that individuals with mild to moderate disease severity (in the present study, at Hoehn and Yahr levels II and III; in the study by Behrman et al,3 Hoehn and Yahr levels II and III and a few with level IV staging) can distinguish between specific instructions and produce movement nuanced to these instructional distinctions. Furthermore, evidence of instructional set effectiveness is consistent with a recent review that noted stronger support for gait-related physical therapy interventions that combined conventional physical therapy with the provision of external visual or auditory cueing than for conventional physical therapy alone in individuals with PD.6 It seems reasonable to suggest that future refinements in physical therapy interventions for people with PD may be enhanced by recognition of the potential of particular forms of instructions to promote more optimal control of movement.

A relatively large and remarkably consistent body of research is accumulating to suggest that instructions to individuals to adopt an external focus of attention are more beneficial than are instructions inducing an internal focus. In our within-subject design, we found again that instructions to focus attention (concentration) on the intended movement effect ("focus on minimizing movements of the inflatable disk") produced greater reduction in postural sway than instructions inducing an internal or body-related focus ("focus on minimizing the movement of your feet") or the control condition with no explicit focus instruction. The finding that control conditions (if they are included) produce very similar performances as internal focus conditions has been consistent across studies. This finding may suggest that participants "naturally" tend to adopt an internal focus, and, more importantly, it indicates that an external focus results in enhanced performance or learning. Interestingly, clinicians have reported that individuals with PD may be aware of their need for external cueing; one individual with PD was observed to remove her belt and place it in a straight line on the floor ahead of her to assist in gait initiation (Carolee J Winstein, PT, PhD, FAPTA; personal communication; December 5, 2008). In the perhaps 50 studies that used appropriate experimental designs to compare the effectiveness of external versus internal foci (or control conditions), we have not come across any exceptions to the superiority of an external focus. Conditions in the present study were counterbalanced for order and each individual encountered all conditions within a relatively short time frame within a single testing session, ensuring that differences in movement effectiveness were not a function of which condition was experienced first, medication-related timing, cognitive capabilities, or other aspects of disease severity within the sample.

It should be pointed out that an external focus directed at the intended movement effect facilitates the achievement of that effect or movement goal. This is independent of what that goal might be (eg, a reduction of postural sway during standing, quick movement adjustments to maintain equilibrium during dynamic balance tasks). In fact, evidence for the motor system's capability to automatically achieve a desired movement outcome also comes from studies examining suprapostural task performance.7–9 These studies have shown that the healthy motor control system is able to optimize the control of posture as a function of the performer's suprapostural task goal (eg, focusing visually, pointing at a target, holding an object still). Thus, tasks such as carrying a tray10 would not be considered as "competing" with the postural task of walking. Rather, the gait pattern would be expected to adjust as a function of the suprapostural task goal of keeping the tray still. Importantly, the achievement of the suprapostural goal and ensuing regulation of postural control can be enhanced further by inducing an external relative to an internal focus on the suprapostural task.11–13 Regardless of the use of a suprapostural task or one with another movement goal, there will be some level of challenge, albeit different across individuals, that would be expected to tax and exceed their available attentional resources, resulting in poor performance on a secondary, and sometimes primary, task. This dual-task breakdown might be forestalled or limited with external attentional focus instructions—which have been shown to reduce attentional demands14—but this effect has yet to be demonstrated directly.

We concur with Morris in noting that the generalizability of the attentional focus effect awaits further evaluation. We would think that evidence of sustainable effects and of the potential for portable self-instruction3 for individuals at different stages in their disease time course would be of particular importance. The external attentional focus advantage has been found across a wide range of non-PD samples (from children to adults and novice learners to more-expert motor performers to individuals following stroke) and with a variety of movement tasks (from discrete sport skills to fundamental movements such as balance, jumping, and ballistic actions) with diverse movement requirements (from aiming accuracy to force production to reductions in postural sway, to productions of large movement amplitudes, to open and closed loop control).15 Therefore, we might speculatively predict that individuals with less impairment than that found in our present sample may find benefit in carefully worded external focus instructions. In addition, they may find it for movement tasks other than the type of balance task used in the present study, although the impact may be most evident for tasks that are of relatively moderate to high challenge for the individual. Clearly, however, extensions to individuals with greater impairment should be undertaken with caution; this form of intervention invokes cognitive and attentional, as well as motoric, abilities that may all be impaired in people with PD.16 However, the benefits for those individuals at risk for movement disorders may make careful implementation and evaluation of particular value. Furthermore, attentional focus probably is most relevant as an integrated feature of otherwise effective interventions.6,17 Assumptions about the residual and latent capabilities of individuals with diseased neuromotor systems to mitigate impairment and enhance activity and participation will continue to be challenged,16,18 and principled use of available movement science seems important.

As Rubinstein and colleagues noted about PD: "One of the most interesting features of PD is that, despite severe motor symptoms, patients are sometimes still able to perform complex movements almost normally under certain conditions... . It appears that the underlying problem has more to do with motor control than with actual motor function. The challenge lies in enabling patients to access this ability at will and to use it in normal, daily function."6(p1149)


   References
 

  1. Morris ME. Commentary on "External focus instructions reduce postural instability in individuals with Parkinson disease." Phys Ther. 2009;89:169–170.[Free Full Text]
  2. Wulf G, Landers M, Lewthwaite R, Töllner T. External focus instructions reduce postural instability in individuals with Parkinson disease. Phys Ther. 2009;89:162–168.[Abstract/Free Full Text]
  3. Behrman AL, Teitelbaum P, Cauraugh JH. Verbal instructional sets to normalize the temporal and spatial gait parameters in Parkinson's disease. J Neurol Neurosurg Psychiatry. 1998;65:580–582.[Abstract/Free Full Text]
  4. Landers M, Wulf G, Wallmann H, Guadagnoli MA. An external focus of attention attenuates balance impairment in Parkinson's disease. Physiotherapy. 2005;91:152–185.[CrossRef][Web of Science]
  5. Yogev-Seligmann G, Hausdorff JM, Giladi N. The role of executive function and attention in gait. Mov Disord. 2007;23:329–342.
  6. Rubinstein TC, Giladi N, Hausdorff JM. The power of cueing to circumvent dopamine deficits: a review of physical therapy treatment of gait disturbances in Parkinson's disease. Mov Disord. 2002;17:1148–1160.[CrossRef][Web of Science][Medline]
  7. Balasubramaniam R, Turvey MT. The handedness of postural fluctuations. Hum Mov Sci. 2000;19:667–684.
  8. Riley MA, Stoffregen TA, Grocki MJ, Turvey MT. Postural stabilization for the control of touching. Hum Mov Sci. 1999;18:795–817.[CrossRef][Web of Science]
  9. Stoffregen TA, Pagulayan RJ, Bardy BG, Hettinger LJ. Modulating postural control to facilitate visual performance. Hum Mov Sci. 2000;19:203–220.[Web of Science]
  10. Canning CG. The effect of directing attention during walking under dual-task conditions in Parkinson's disease. Parkinsonism Relat Disord. 2005;11:95–99.[Web of Science][Medline]
  11. McNevin NH, Wulf G. Attentional focus on supra-postural tasks affects postural control. Hum Mov Sci. 2002;21:187–202.[CrossRef][Web of Science][Medline]
  12. Wulf G, Mercer J, McNevin NH, Guadagnoli MA. Reciprocal influences of attentional focus on postural and supra-postural task performance. J Mot Behav. 2004;36:189–199.[Medline]
  13. Wulf G, Weigelt M, Poulter DR, McNevin NH. Attentional focus on supra-postural tasks affects balance learning. Q J Exp Psychol. 2003;56:1191–1211.
  14. Wulf G, McNevin N, Shea CH. The automaticity of complex motor skill learning as a function of attentional focus. Q J Exp Psychol A. 2001;54:1143–1154.[CrossRef][Web of Science][Medline]
  15. Wulf G. Attention and Motor Skill Learning. Champaign, IL: Human Kinetics Inc; 2007.
  16. Morris ME. Locomotor training in people with Parkinson disease. Phys Ther. 2006;86:1426–1435.[Abstract/Free Full Text]
  17. Farley BG, Koshland GF. Training BIG to move faster: the application of the speed-amplitude relation as a rehabilitation strategy for people with Parkinson's disease. Exp Brain Res. 2005;167:462–467.[CrossRef][Web of Science][Medline]
  18. Fisher BE, Wu AD, Salem GJ, et al. The effect of exercise training in improving motor performance and corticomotor excitability in people with early Parkinson's disease. Arch Phys Med Rehabil. 2008;89:1221–1229.[Medline]

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This Article
Right arrow Extract Freely available
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Right arrow Submit a response
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Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wulf, G.
Right arrow Articles by Töllner, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wulf, G.
Right arrow Articles by Töllner, T.
Related Collections
Right arrow Balance
Right arrow Motor Control and Motor Learning
Right arrow Parkinson Disease and Parkinsonian Disorders
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Copyright © 2009 by the American Physical Therapy Association.