Association Between Weekly Strength Training Load and Perceived Physical Performance in Non-Professional Soccer Players

• Soccer players sample (Other): Active non-professional (amateur) soccer players.

Primary outcomes

• Measurement of perceived physical performance [Screening visit]: This variable will be assessed using the Spanish version of the Perceived Performance in Sports Questionnaire. This instrument measures athletes' subjective evaluation of their own performance during competition or sport practice. It consists of five items rated on a 1-5 Likert scale, with the final score calculated as the mean of the items; higher scores indicate better perceived performance. As no specific cut-off points are established, the score will be interpreted as a continuous variable.

Secondary outcomes

• Measurement of weekly strength training load [Screening visit]: Weekly strength training load will be quantified using the session Rating of Perceived Exertion (sRPE; Borg CR-10). Participants will report session duration and perceived intensity (0-10) for all strength sessions in the previous week. Weekly load will be calculated as the sum of sRPE × duration (minutes) across sessions.
• Measurement of perceived fatigue [Screening visit]: This variable will be assessed using the Spanish version of the Fatigue Severity Scale (FSS). This self-reported questionnaire evaluates the impact of fatigue on daily functioning and consists of nine items rated on a 1-7 Likert scale. The final score is calculated as the mean of the items, with higher values indicating greater perceived fatigue; a mean score ≥4 is considered indicative of clinically significant fatigue.
• Measurement of motivation toward training and sport participation [Screening visit]: This variable will be assessed using the Spanish version of the Behavioral Regulation in Exercise Questionnaire-2 (BREQ-2). This self-reported instrument, grounded in Self-Determination Theory, evaluates different types of motivational regulation toward exercise. It consists of 19 items distributed across the dimensions of amotivation, external regulation, introjected regulation, identified regulation, and intrinsic motivation. Higher scores in autonomous regulation, particularly intrinsic motivation, are associated with greater adherence to and engagement in sport practice.

Other outcomes

• Measurement of age [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be measured in years.
• Measurement of gender [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be recorded as a dichotomous variable (male/female).
• Measurement of playing position [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be recorded as an ordinal variable (goalkeeper / defender / midfielder / forward).
• Measurement of competitive category [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be recorded as an ordinal variable (e.g., first regional division / second regional division, etc.).
• Measurement of soccer-specific experience [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be measured as a continuous variable, defined as the number of competitive seasons played.
• Measurement of average match playing time [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be recorded as an ordinal variable (<45 minutes / 45-90 minutes / >90 minutes).
• Measurement of body mass index [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be calculated from body mass and height (kg/m²).
• Measurement of overall weekly training load [Screening visit]: This confounding or moderating variable, used to control for individual characteristics, will be assessed as the mean perceived exertion of all training sessions (strength training plus field-based sessions) using a 0-10 rating of perceived exertion scale.

Sex: Male, ages: 18 Years to 40 Years, accepts healthy volunteers

Inclusion Criteria:

* Age between 18 and 40 years.
* Competing in the 3ª RFEF category.
* Male sex.
* Having at least two years of seniority in federated football.
* Signing the informed consent document.

Exclusion Criteria:

* Athletes with injuries lasting more than 3 months during the last season.
* Participation in fewer than two weekly group training sessions (one or none).
* Having undergone lower-limb surgery in the last 24 months.
* Players who, despite being able to attend training sessions on a continuous basis, have a regular occupational activity that causes such a high physical workload that their sports performance is limited in training and/or competition.