This study aims to determine whether gait physiotherapy combined with motor imagery exercises has a superior effect than gait physiotherapy without motor imagery in people with Parkinson's disease. To do this, a six-week training program will be carried out twice a week, where walking exercises and motor imaging will be performed in the experimental group while walking exercises only, will be conducted in the control group. Motor imagery exercises consist of developing a mental exercise by which an individual rehearses or simulates a given action. We hypothesize that participants who perform motor imagery exercises have better results than participants who train without imagery exercises. To analyze the effect of the programs will be assess the gait, the functionality in activities of daily living, the motor capacity, and the perception of the quality of life of the participants.

Background:

Motor imagery (MI) is a novel technique in neurorehabilitation. Current evidence supports the ability of people diagnosed with Parkinson's disease (PD) to carry out this technique. However, the trials that assess its effectiveness in this pathology are scarce. In some physical rehabilitation programs, MI is introduced to conventional treatment or, MI can be combined with observation of images or neurofeedback. At present, the effect of this technique has been studied in highly heterogeneous variables, including both motor and cognitive abilities or performance of activities of daily living. The evidence seems to indicate that the introduction of MI to conventional treatment, with an adequate dose, may induce greater benefits over people with PD in early stages (I-III on the Hoehn and Yahr scale), especially in daily actions and movements functional such as gait, regardless of medication. However, the small sample size of the trials and the use of non-validated scales and non-objective tests, make it necessary that the results be viewed with caution. On the other hand, the cost-benefit ratio of the therapy, its benefits and its easy application are significant factors to take into account when adding MI to physiotherapy treatment in people with PD.

General objective: To determine whether gait training combined with MI exercises has a superior effect on gait, functionality in activities of daily living, motor capacity, and the perception of the quality of life in people with PD, which gait training without MI.

Specific objectives:

1. To study the validity of the instrumental technique available for the evaluation of gait and the intra- and inter-rater reliability with the same tool in healthy subjects.
2. To check the effect, in the short and medium-term, of a gait training program combined with MI in people diagnosed with PD.
3. To compare the effects of the gait and MI training program with the effects obtained through a gait rehabilitation program without MI exercises.
4. To contrast the gait pattern of people with PD before and after undergoing a rehabilitation program with MI, with that of healthy older people of the same age, sex, and height.
5. To observe the differences in the biomechanics of gait between the hemibody most affected by the signs of PD and the hemibody with less clinical alteration, before and after performing a gait training program combined with MI exercises.

Materials and Method:

The evaluation session will be carried out three times: before the treatment, at the end of the intervention, and 8-weeks after the intervention has finished. In each evaluation session, a clinical and biomechanical measurement will be carried out. The biomechanical evaluation will be done using 7 inertial sensors in a 10-meter walk corridor. The inertial sensor or inertial measurement unit (IMU) is made up of three different sensors: gyroscope, accelerometer, and magnetometer, capable of collecting information on the turns, linear acceleration, and magnetic north with respect to the earth's magnetic field. The part of the clinical evaluation includes the assessment of the functionality in the activities of daily living, the motor capacity, and the perception of the quality of life through different questionnaires and assessment scales.

Intervention:

Both, the experimental and control groups of this study, will perform an identical gait physiotherapy program, however, motor imagery exercises will be included in the experimental group.

The gait exercises are aimed at improving specific gait characteristics, so they will include:

• Exercises for length stride: walk with visual cues on the ground to reach a certain stride length, walk with horizontal poles at a height of 2 cm, walk over steps, treadmill walk.
• Exercises for Cadence training using a metronome.
• Exercises for gait velocity training by combining the visual and auditory feedback provided in previous exercises and on the treadmill
• Exercises for kinematic milestones during the stance and oscillation phase of gait through the mobility of the ankle, knee, and hip joints.

The motor imagery exercises will be performed in supine position on a stretcher, before each gait exercise. The instructions will be administered through the physiotherapy voice. The participant with closed eyes imagines himself performing the gait task while the general guidelines that guide the cognitive process are given. The instructions describe how the person is from the starting position and the different body movements that he must pay attention to during the imagining process. Through the instructions, the participant creates an image of himself and perceives the kinesthesia while performing the exercise. The duration of each motor imagery exercise is 8 minutes.

The inclusion criteria are:

1. Diagnosed with PD according to the United Kingdom Parkinson's Disease Society Brain Bank diagnostic scale
2. Independent walk in a 10-meter corridor
3. Normal cognitive state, determined by the Mini-Mental State Examination with a score >25
4. Stable medication from the month before the start of the study until the t2 assessment.

Likewise, the exclusion criteria are:

1. Additional neurological condition different from PD
2. Disease or musculoskeletal acute alteration that limits mobility or balance
3. Lower extremities asymmetries >1 cm
4. Report pain on the Visual Analog Scale
5. Suffer from blindness, deafness, or any other visual/hearing impairment or pathology that may influence the ability to understand instructions and carry them out
6. Significant tremor that may interrupt the MI exercise
7. To perform other physical therapies or sports during the trial or the two months before.

All measured and recorded data will be shared through the publications made and through their supplementary material.

To ensure masking, the raters physiotherapist, and data analysis researcher, will be blinded to the participant's allocation. Although participants and treating physiotherapists cannot be totally blinded to the intervention performed, the hypothesis and objectives of the study will be hidden from them. At the same time, all participants will be instructed not to disclose information regarding their intervention to the raters' physiotherapists.