Background: One of the most disturbing motor symptoms in Parkinson's disease (PD) is gait disturbance. Clinicians often use various verbal instructions to correct abnormal gait patterns, and the most commonly used instruction is 'lift the foot up and make big steps.' Despite immediate performance improvement, people with PD are reluctant to walk outdoors with this exaggerated walking strategy because it makes them feel embarrassed, unbalanced, and fatigue easily. Since people with PD walk with flat foot, the investigators propose that an instruction emphasizing heel-strike at foot contact may be effective. The action of heel-strike could function as a foot rocker and facilitate forward progression of the limb. Heel-strike could also increase the effective limb length and reduce energy cost during walking. Thus, emphasizing heel-strike during gait training may restore near-normal gait pattern and enhance the patients' compliance.~When delivering verbal instructions, clinicians should also consider the attentional focus of the instruction. Evidence has shown that instructions with external focus of attention (EF) is more beneficial than internal focus of attention (IF) for motor performance and learning. However, most of the gait-related instructions for PD are IF. The investigators thus aim to design a novel EF instruction and determine whether people with PD can benefit more from EF than IF instruction.~Objectives: The first aim of this study is to investigate the effects of verbal instruction emphasizing heel-strike during gait training in people with PD. The second aim is to further determine whether an instruction with EF will induce greater training benefits than IF.~Methods: Two experiments will be conducted in this study. In experiment 1, 60 individuals with idiopathic PD will be randomized into the heel-strike (HS), big-step (BIG), and control (CON) groups. All participants will receive 12 sessions of treadmill and over-ground gait training. During training, the participants will be instructed to 'strike the ground with the heel,' 'lift the foot up high,' or 'swing the arms' in the HS, BIG, or CON group, respectively. The participants will be assessed before, immediately after, and 4 weeks after the interventions. The primary outcome will be gait performance, and the secondary outcomes will include finger sequence task, Montreal Cognitive Assessment test, Stroop Color-Word test, Unified Parkinson's Disease Rating Scale, 5 times sit to stand test, Timed Up and Go test, Fatigue Severity Scale, Activities-Specific Balance Confidence Scale, Parkinson's Disease Questionnaire-39, New Freezing of Gait Questionnaire and Geriatric Depression Scale. Transcranial magnetic stimulation will be used to examine the changes of corticomotor excitability associated with the interventions.~In the 2nd experiment, 46 individuals with PD will be randomized into the internal focus heel-strike (IF-HS) or external focus shoe-strike (EF-SS) group. The instruction for the IF-HS group will be 'strike the ground with the heel,' and 'strike the ground with the shoe-heel' for the EF-SS group. The other intervention and testing procedures will be the same as experiment 1.~Group × time repeated measures analysis of variance (ANOVA) will be used to compare the intervention effects. The partial eta square (η2) will be calculated to determine the magnitude of group differences. A significance level will be set at α=0.05.
Background: One of the most disturbing motor symptoms in Parkinson's disease (PD) is gait disturbance. Clinicians often use various verbal instructions to correct abnormal gait patterns, and the most commonly used instruction is 'lift the foot up and make big steps.' Despite immediate performance improvement, people with PD are reluctant to walk outdoors with this exaggerated walking strategy because it makes them feel embarrassed, unbalanced, and fatigue easily. Since people with PD walk with flat foot, the investigators propose that an instruction emphasizing heel-strike at foot contact may be effective.~When delivering verbal instructions, clinicians should also consider the attentional focus of the instruction. Evidence has shown that instructions with external focus of attention (EF) is more beneficial than internal focus of attention (IF) for motor performance and learning. However, most of the gait-related instructions for PD are IF. The investigators thus aim to design a novel EF instruction and determine whether people with PD can benefit more from EF than IF instruction.~Objectives: (1) To investigate the effects of verbal instruction emphasizing heel-strike during gait training in people with PD. (2) To further determine whether an instruction with EF will induce greater training benefits than IF.~Methods: Two experiments will be conducted in this study. In experiment 1, 60 individuals with PD will be randomized into the heel-strike (HS), big-step (BIG), and control (CON) groups. All participants will receive 12 sessions of gait training with the specific verbal instruction allocated for each group. The participants will be assessed before, immediately after, and 4 weeks after the interventions. The primary outcome will be gait performance, and the secondary outcomes will include measurements of cognitive and behavioral functions. Additionally, transcranial magnetic stimulation will be used to examine the changes of corticomotor excitability associated with the interventions.~In the 2nd experiment, 46 individuals with PD will be randomized into the internal focus heel-strike (IF-HS) or external focus shoe-strike (EF-SS) group. Except for the verbal instruction provided to the participants, other intervention and testing procedures will be the same as experiment 1.~Group × time repeated measures analysis of variance (ANOVA) will be used to compare the intervention effects among the groups, and a significance level will be set at α=0.05.