Muscle Injury RTP Design in Football; Effects of Backward Design vs Forward Design.

Capturing and Recruiting Participants

Since the players are from the same club and suffer muscle injuries, they will be included in the control and intervention groups for three years. The following section will explain that the sampling technique is consecutive and that participants can take part in the study several times, as long as they have a muscle injury diagnosed by resonance. Relapses of the same injury or injuries in the same or different muscle groups will also be included in the sample. The head of the club's medical service and collaborating researcher, Dr. José María Villalón Alonso, will recruit the participants. After the diagnostic test (MRI) is performed and the diagnosis and prognosis are established, the participants will be handed over to the recovery specialists, who will design the RTP. The specialists and the participants (players) will be blinded in the same way.

Allocation Procedure/Randomization

Subjects (muscle injuries) have the same probability (50%) of being allocated to the control or intervention group, regardless of previous allocations.

Justification of Sample Size

A type of consecutive sampling will be carried out based on the average probability that a soccer player will suffer a muscular injury. On average, each player will suffer 0.6 muscular injuries per season. In a team of 25 soccer players, this translates to an average of 15 muscular injuries per season. By contrasting this data with the club's database, we can verify the accuracy of this estimate. According to this statistical data, the population from which we will extract the sample will be the total number of muscle injuries suffered by the two teams of Club Atlético Madrid over three years:

0.6 (injuries) x 50 (players) x 3 years = 90 muscle injuries. Using the Grammo sample calculator with a relative error of 5% and a 95% confidence interval, we will calculate the necessary sample size for the sample to be representative, which will be N = 74.

Statistical Analysis Plan:

Phase 1: Use Levene's test to check if the variances of the control and intervention groups are equal.

Phase 2: Use a t-test to determine if there is a significant difference between the means of the control and intervention groups, and to establish whether the null hypothesis (H0) or the alternative hypothesis (HA) is true.

Phase 3: Perform a bivariate study of the relationship between anxiety (dependent variable) and estimated prognosis (independent variable) using Pearson's correlation coefficient.

Phase 4: Conduct a multivariate study through multiple regression between the dependent variable, sleep quality, and the independent variables, age, type of affected tissue, and cortisol level.

Phase 5: Perform a multivariate study through simple linear regression between the dependent variable, anxiety, and the independent variable, previous injuries in the same musculature.

Ethical and Legal Aspects:

Compliance with the standards of Good Clinical Practice, the Declaration of Helsinki, the Oviedo Convention, and the Personal Data Protection and Guarantee of Digital Rights Act (LO 3/2018, December 5, 2018), as well as the regulations for managing clinical histories.

The investigator undertakes to comply with the aforementioned rules throughout the development of the research protocol, as well as in the presentation to this ethics committee, for which the investigator must provide a certificate of Good Clinical Practice (GCP). The collaborating investigators also have this GCP certificate.

Informed Consent Form:

The patient information sheet and informed consent form are both attached in Annexes 1 and 2.

The confidentiality of information collected in the context of the study is guaranteed.

Data Controller: Óscar Vicente Rodríguez TLF: 699 874 059 Email: [email protected]

Purpose of data collection: Clinical and epidemiological research.

Maximum period of data retention: The data will be kept for four years (three years for the duration of the study and one extra year for future research).

Processing, communicating, and transferring the personal data of all participating subjects will comply with the provisions of Organic Law 3/2018 of December 5 on the protection of personal data and the guarantee of digital rights.

In accordance with the aforementioned legislation, you may exercise your rights of access, rectification, deletion, opposition, and limitation of data processing. You may also transfer your data to an authorized third party (portability). For these requests, please contact the principal investigator responsible for processing at [email protected] or C/Moreno Torroba 10, 1o B, CP. 28220 Majadahonda, Madrid.

The data will be computerized and incorporated into an automated personal data system that complies with all security measures for restricted access, as described in this document.

To guarantee the confidentiality of the obtained information:

Your data and the sample will be identified by a code, and only the study physician and their collaborators will be able to relate this data to you and your medical history. Therefore, your identity will not be disclosed to anyone except in case of medical emergency or legal or administrative requirement.

Only the essential data necessary for the study will be transmitted to third parties and other countries. In no case will the data contain information that can directly identify you, such as your name, initials, address, or social security number. If this transfer occurs, it will be for the aforementioned study purposes and will guarantee confidentiality with at least the level of protection guaranteed by the legislation in force in our country.

Access to your personal information will be restricted to the study physiotherapist, collaborators, health authorities, the Balearic Islands Research Ethics Committee, and authorized personnel when required to verify the study's data and procedures, always maintaining confidentiality in accordance with current legislation.

You may contact the Spanish Data Protection Agency with any claims related to the processing of your personal data.

The handling of biological samples will be in accordance with Law 14/2007 and Royal Decree 1716/2011.

Saliva samples to determine cortisol levels will be collected at the Ciudad Deportiva Atlético de Madrid clinic on three occasions: at the beginning of the RTP, after the magnetic resonance imaging diagnosis, halfway through the established prognosis, and the day before the RTP ends. The analysis will be performed at the same clinic, where, at the end of the cortisol measurement, the saliva will be discarded and only the recorded cortisol value will be kept.

Any risks associated with the procedure used to collect these samples are covered by the study insurance.

The sample will be coded and treated confidentially throughout this study. A code will be used to link the sample to you, and only the investigator and his staff will be able to decipher it to preserve your identity.

If additional data or samples are needed, your physical therapist will contact you to request your cooperation.

You will be informed of the reasons and asked again for your consent if necessary.

It will not receive any economic benefits from the donation of samples or the transfer of provided data, nor will it have any rights to possible commercial benefits from discoveries resulting from the research.

The samples will be analyzed in the Ciudad Deportiva Atlético de Madrid laboratory and stored for four years in case additional analyses related to the study's objectives are necessary. The person responsible for the samples will be the study promoter during this process.

At the end of the research period, your sample may be:

• Destroyed
• Anonymized (i.e., the link between the sample and you will be completely destroyed so that neither the researcher nor any other team member will be able to identify to whom your sample belongs again).
• Incorporated into a collection managed by researcher Óscar Vicente Rodríguez at the Ciudad Deportiva Atlético de Madrid so that it can continue to be used in the "Stress and Muscle Injury" study and line of research. ́

Samples are stored in the Ciudad Deportiva Atlético de Madrid biobank for use in other research projects, which may be unrelated to the initial study for which consent was given. The biobank may provide samples to authorized projects, including those abroad, with prior approval from the scientific and ethics committees. You may contact the biobank to obtain information on projects in which your samples were used.

Insurance Policy or Justification of Absence for Experimental Studies

Mr. Óscar Vicente Rodríguez is the principal investigator and has the following identification number: 35.572.548, and is a member with no. 1224, is registered in the Collective Policy of Professional Civil Responsibility, to which the Official College of Physiotherapists of the Balearic Islands adheres, with number 531000009 from A.M.A. (Agrupación Mutual Aseguradora - La Mutua de los Profesionales Sanitarios). Annex 3.

Commitment to publishing the results

The principal investigator is committed to publishing the results, regardless of their nature, since there is no conflict of interest. This trial will be part of the doctoral student's (principal investigator) thesis, which guarantees the publication of the results to improve the design of the RTP process.

Financial report and source of financing

The project has no private funding other than the 3,235.45 euros provided by PI Oscar Vicente Rodriguez for the cortisol ELISA measurement kits, Oura rings, and tablets used to record expenses. The MRI and radiological report expenses are free for the club due to the entity's nature, with no conflict of interest. The same applies to the team of statisticians who can analyze the results. They are part of the UIB and collaborate with doctoral theses. This essay is one such work. Regarding the CEIm of the Balearic Islands, this trial is exempt from fees (see the documentation), as it is part of the UIB's Doctoral School studies.

Inclusion criteria

• Male soccer players.
• Diagnosed with a muscle injury via magnetic resonance imaging (MRI) during the three year study period.
• They will all belong to the same club.
• Age will be between 18 and 40 years old.

Exclusion criteria

• Patients (Muscle injuries) that do not cause players to miss training or competitions.
• Patients voluntarily decide not to participate in the study or abandon the RTP process due to transfers or other exceptional causes.