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Papa EV1, Foreman KB2, Dibble LE2
1Idaho State University Health Science Center, Physical & Occupational Therapy, Meridian, United States, 2University of Utah, Physical Therapy, Salt Lake City, United States
Background: Falls are a major source of morbidity and disability in persons with Parkinson disease (PD). While the role of cardinal motor symptoms of the disease (rigidity, bradykinesia, tremor, and postural instability) have been linked to fall risk in this population, the role of associated PD-related deficits is still misunderstood. For example, there has been little research done to investigate the effect of fatigue on one of the cardinal signs of PD, postural instability. In fact, numerous studies have already established links between muscle fatigue and increased fall risk in neurologically healthy older adults. The lack of information about the effect of fatigue on balance in PD leaves a critical gap in our knowledge and understanding of fall risk in this population.
Purpose: The purpose of this investigation was to characterize the effect of muscle fatigue on anticipatory postural control during a self-initiated balance task in persons with PD. We hypothesized that muscle fatigue would decrease joint angular displacements and the magnitude of the anticipatory postural adjustment, while increasing the variability of the center of pressure (COP) trajectory throughout the balance task.
Methods: Lower extremity kinetic and kinematic data were gathered on 7 persons with PD (64.7+9.1) (H&Y 2.0+0.4). Participants performed a single limb balance test prior to and immediately following a bout of lower-extremity fatiguing exercise. Outcome measures included reach distance of the extended limb, joint angular displacements, peak anticipatory postural adjustment, and COP variability under the stance limb during the balance task. Data were gathered using a Vicon 10-camera motion analysis system and an AMTI-OR6 force platform. Differences in postural control were assessed using pre- and post-fatigue outcomes via paired samples t-tests. All analyses were performed using SPSS version 21.0.
Results: The magnitude of the anticipatory postural adjustment was decreased in the fatigued condition (t(6)=2.66, p=0.037, d=1.0) and COP variability under the stance limb was increased following the bout of muscle fatigue (t(6)= -2.51, p=0.046, d=0.95). Hip angular displacement of the support limb trended toward a decline following fatiguing exercise, but did not achieve statistical significance (t(6)=2.23, p=0.067). While statistical significance was not met, a large effect size was noted for the effect of fatigue on hip angular displacement (d=0.84).
Conclusion(s): Muscle fatiguing exercise portends to exacerbate the cardinal motor symptom of postural instability during balance tasks in persons with PD. This exacerbation appears to be driven by a decreased anticipatory postural adjustment during the initiation of the postural task. The trend toward decreased angular displacement of the hip during single limb support also suggests an exacerbation of hypokinesia. The increased variability of the COP profile under the stance limb represents a decline in stability during the execution of the task.
Implications: Muscle fatigue has negative consequences on anticipatory postural control in individuals with PD. Physical therapists should be aware of the potential for decreased postural stability following bouts of fatiguing exercise.
Keywords: Parkinson disease, postural control, muscle fatigue
Funding acknowledgements: This work was unfunded
Purpose: The purpose of this investigation was to characterize the effect of muscle fatigue on anticipatory postural control during a self-initiated balance task in persons with PD. We hypothesized that muscle fatigue would decrease joint angular displacements and the magnitude of the anticipatory postural adjustment, while increasing the variability of the center of pressure (COP) trajectory throughout the balance task.
Methods: Lower extremity kinetic and kinematic data were gathered on 7 persons with PD (64.7+9.1) (H&Y 2.0+0.4). Participants performed a single limb balance test prior to and immediately following a bout of lower-extremity fatiguing exercise. Outcome measures included reach distance of the extended limb, joint angular displacements, peak anticipatory postural adjustment, and COP variability under the stance limb during the balance task. Data were gathered using a Vicon 10-camera motion analysis system and an AMTI-OR6 force platform. Differences in postural control were assessed using pre- and post-fatigue outcomes via paired samples t-tests. All analyses were performed using SPSS version 21.0.
Results: The magnitude of the anticipatory postural adjustment was decreased in the fatigued condition (t(6)=2.66, p=0.037, d=1.0) and COP variability under the stance limb was increased following the bout of muscle fatigue (t(6)= -2.51, p=0.046, d=0.95). Hip angular displacement of the support limb trended toward a decline following fatiguing exercise, but did not achieve statistical significance (t(6)=2.23, p=0.067). While statistical significance was not met, a large effect size was noted for the effect of fatigue on hip angular displacement (d=0.84).
Conclusion(s): Muscle fatiguing exercise portends to exacerbate the cardinal motor symptom of postural instability during balance tasks in persons with PD. This exacerbation appears to be driven by a decreased anticipatory postural adjustment during the initiation of the postural task. The trend toward decreased angular displacement of the hip during single limb support also suggests an exacerbation of hypokinesia. The increased variability of the COP profile under the stance limb represents a decline in stability during the execution of the task.
Implications: Muscle fatigue has negative consequences on anticipatory postural control in individuals with PD. Physical therapists should be aware of the potential for decreased postural stability following bouts of fatiguing exercise.
Keywords: Parkinson disease, postural control, muscle fatigue
Funding acknowledgements: This work was unfunded
Topic: Neurology: Parkinson's disease; Human movement analysis
Ethics approval required: Yes
Institution: University of Utah
Ethics committee: Institutional Review Board
Ethics number: IRB_00056577
All authors, affiliations and abstracts have been published as submitted.
