Here is the design of a clinical trial:

Official Title: Investigating the Effect of Motor Imagery With or With no Visual Neurofeedback on Grasping Capabilities After C6-C7 Tetraplegia: a Multicentric Randomized Controlled Trial.

Included conditions:
- Individuals With C6-C7 Tetraplegia (AIS A or B)

Study Armgroups:
- {'label': 'Motor imagery combined with neurofeedback (MINF)', 'type': 'EXPERIMENTAL', 'interventionNames': ['Behavioral: Motor imagery combined with neurofeedback (MINF)']}
- {'label': 'Motor imagery (MI)', 'type': 'ACTIVE_COMPARATOR', 'interventionNames': ['Behavioral: Motor imagery (MI)']}
- {'label': 'Control (C)', 'type': 'SHAM_COMPARATOR', 'interventionNames': ['Behavioral: Control (C)']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Motor imagery combined with neurofeedback (MINF)', 'description': '7 individuals with C6-C7 tetraplegia randomize in the experimental group consisting in motor imagery practice combined with visual neurofeedback (NF - i.e. performance of the imagined movement).\n\nIntervention consists in a total of 15 sessions repeated 3 times a week and lasting 5 weeks. Each session will last 45 minutes. An experienced physical therapist supervised all sessions. After each imagined movement, the NF based on brain activity measured by electroencephalography is display on a screen.', 'armGroupLabels': ['Motor imagery combined with neurofeedback (MINF)']}
- {'type': 'BEHAVIORAL', 'name': 'Motor imagery (MI)', 'description': '7 individuals with C6-C7 tetraplegia randomized in the active comparator group consisting in motor imagery practice alone without visual NF. This means that the performance of the imagined movement is not displayed to the participants.\n\nIntervention consists in a total of 15 sessions repeated 3 times a week and lasting 5 weeks. Each session will last 45 minutes. An experienced physical therapist supervised all sessions.', 'armGroupLabels': ['Motor imagery (MI)']}
- {'type': 'BEHAVIORAL', 'name': 'Control (C)', 'description': '7 individuals with C6-C7 tetraplegia randomized in the sham comparator group consisting in imagining geometric shapes by visualization. Shapes are successively displayed on a screen.\n\nIntervention consists in a total of 15 sessions repeated 3 times a week and lasting 5 weeks. Each session will last 45 minutes. An experienced physical therapist supervised all sessions.', 'armGroupLabels': ['Control (C)']}

Primary Outcomes:
- {'measure': 'Wrist extension angle in degree during grasping with 3D motion analysis system', 'description': 'Individuals with C6-C7 tetraplegia extend their wrist to grasp using tenodesis. Specifically, the wrist extension shortens the tendons of fingers and thumbs flexors that elicit either a palmar or a lateral grip. A complete reach-to-grasp movement will be recorded using a 3D motion analysis system (Vicon Motion Systems Ltd. UK). Wrist extension angle in degree will be measure during grasping when the object is grasped.', 'timeFrame': 'Up to 19 weeks'}

Please estimate the sample size based on the assumption: 
Alpha is set to 5% (0.05), the effect size is medium (f2=0.35), and the calculated power is 85%. No participants are expected to withdraw from the study.
Sample size calculation
        Our sample size calculation is based on data from healthy participants collected during a similar MI intervention. Mateo et al13 reported that wrist extension angle in people with SCI was an average of 17.8Â° before MI tenodesis grasp training and increased up to an average of 26.9Â° after, thus representing a medium effect size.13 We expect this MI-related gain to increase by a further 10Â° in participants who receive MI training with neurofeedback. Based on these assumptions, we used the R software package âpwrâ and the associated function to compute the power for a general linear model âpwr.f2.testâ.57 We considered an interaction between GROUP (three levels, ie, MI with neurofeedback, MI and control) and VISIT (three levels: baseline grouping visits 1, 2 and 3, visit 4 and visit 5), that is 3Ã3 factorial design. We then computed the degrees of freedom (df) for the numerator (u = (3 â 1)*(3 â 1) = 4); considering n=7 participants in each of the 9 cells (GROUP * VISIT) of the design, a total N of 63, the denominator df was v=63â9=54; with alpha set to 5% (a=0.05) and a medium effect size as previously reported13 (f2=0.35), the calculated power is 85%.57 This indicated that seven participants should be included in each group, thus requiring a total of 21 participants.58 Based on our experience of patient motivation to improve hand-arm function we do not expect any participants to withdraw from the study after giving their consent to participate.