Arm Circumference Measurement

Skeletal Muscle Endurance Tests (Sit-Up, Push-Up, and Pull-Up)

Anaerobic Power Assessment

Bench Press 1RM Test Measurement

Triceps Push-Down 1RM Test Measurement

Hand Grip Strength Test Measurement

Yo-Yo IR1 Test Measurement

Ultrasound (US) Measurements

Determination of Perceived Discomfort Level

Exercise Enjoyment Assessment

Perceived Exertion Level Assessment

Dominant and non-dominant shoulder internal and external rotation strength will be assessed using a Lafayette digital handheld dynamometer. This portable device provides peak force, time to peak force, total test duration, and average force in kilograms, Newtons, and pounds. Participants will receive verbal instructions and complete a familiarization trial before testing. The "make test" technique will be used, in which the examiner stabilizes the device while the participant applies maximal isometric force. All measurements will be taken twice by the same trainer. Prior to testing, a 10-minute warm-up including upper-extremity and shoulder rotation movements will be performed. Participants will then lie supine on a flat surface, and dominant and non-dominant internal and external rotation strength will be measured and recorded (Kesilmiş & Manolya, 2020).

The serve speed test will be conducted in the Hasan Doğan Sports Sciences Gymnasium at Karabük University using official balls (FIVB Beach Championship VLS300 MIKASA). Athletes will begin with a 15-minute warm-up consisting of joint mobility exercises (e.g., knee flexion/extension, shoulder rotation, ankle dorsiflexion), followed by technical movements such as ball-free jumping and running to enhance coordination. Each player will then perform ten practice serves. A total of 196 power-kick serves (28 per participant) will be recorded without opposition. After each isometric exercise, participants will execute four maximal-intensity serves, and ball speed will be determined from these attempts. Athletes will be encouraged to strike the ball with maximum force. A radar device will be positioned 8 m behind the service line and 3 m above the ground to capture serve velocity at a height consistent with ball-hand contact (Buscà et al., 2012). Serve speed will be measured using a standard ra

The arterial occlusion pressures (AOP) of the athletes randomized to the experimental group will be automatically determined using a digital LED-display BFR device (Fit Cuffs BFR, Denmark). Optimal cuff width, occlusion pressure, and exercise procedures have been previously described in the literature (Loenneke et al., 2015; Scott et al., 2015). A 4-inch-wide tourniquet will be applied to the upper arm of the participant's dominant limb. During the exercise, the AOP will be maintained at 60% using the Fit Cuffs BFR Unit (Denmark), and consistent pressure will be applied to the limb throughout the full range of motion. All participants will use the same cuff model, and 60% AOP will be administered with an FDA/CE-approved automatic Smart Cuffs Pro device (Elite, USA), applied to the proximal region of the arm.

After each training session, RPE will be collected using the 6-20 Borg Scale at the end of the session, where 6 indicates "no exertion" and 20 indicates "maximal exertion" (Foster et al., 2021).

Based on prior literature recommending battle ropes measuring 12-15 m in length, 3-5 cm in diameter, and 9-16 kg in weight (Pustina et al., 2017; Tessitore et al., 2006; Ziy et al., 2009), this study will use a 12-m, 3.8-cm diameter, 12-kg rope. Participants will perform wave-style rope exercises in a standing position with feet shoulder-width apart and the trunk flexed forward at approximately 30-45°. The rope will be anchored at its midpoint to a stable object, and participants will grip the ends (5 m ± 5 cm each) and execute bilateral oscillations. The protocol will include three sets of five exercises, with progressive durations across the 8-week period: 15 seconds in Weeks 1-2, 20 seconds in Weeks 3-5, and 25 seconds in Weeks 6-8. Rest intervals between sets will remain consistent at 45 seconds throughout the training program.

Before the training session and without performing any physical activity, arm circumference will be measured using a 300-cm non-elastic measuring tape. Measurements will be taken at a 90° elbow angle from the midpoint of the upper arm, over the biceps muscle (Otman, 2003).

Upper-body and trunk muscular endurance will be assessed using standardized ACSM protocols. Upper-body endurance will be measured with the ACSM push-up test: men will perform standard push-ups, while women will complete kneeling push-ups. The test will stop at volitional fatigue or after two consecutive form errors (chin to mat and full elbow extension). Trunk endurance will be evaluated using the cadence-based YMCA bent-knee sit-up test, performed at one repetition every 2 seconds until volitional fatigue. A valid sit-up requires elbows touching the knees and returning to the starting position in cadence. Upper-body pulling endurance will be tested with a pronated-grip pull-up test. Repetitions must include the chin rising above the bar and full controlled elbow extension. The test ends at volitional fatigue or after repeated form errors. All endurance tests (push-up, sit-up, pull-up) will be performed to volitional fatigue with 2-3 minutes of rest between tests, and the same test

The Wingate Anaerobic Power Test (WAnT) is a widely used 30-second cycling test designed to measure short-term, high-intensity power output and anaerobic energy system capacity (Reiser et al., 2002). Conducted on a Monark 894E ergometer, the test uses a resistance load adjusted to each participant's body mass (Jaafar et al., 2014). Before testing, participants will complete a 4-5 minute warm-up at 60-70 W and 60-70 rpm, including 2-3 short sprints, followed by 3-5 minutes of passive rest. Saddle and handlebar settings will be adjusted so the knee reaches full extension at the lowest pedal position, and feet will be secured with clips. Participants will accelerate to maximal speed without resistance; once they reach 150 rpm, the programmed resistance load will automatically engage. They will then pedal maximally for 30 seconds against this resistance while receiving verbal encouragement (Ozkan, 2007).

Participants will begin with a 5-minute treadmill warm-up at 9 km/h followed by three minutes of light stretching (do Carmo et al., 2021). A specific warm-up will then be performed: 5 reps at 50% of estimated 1RM, followed by 1-2 sets of 2-3 reps at 60-80%. After warm-up, participants will perform single-rep attempts with gradually increasing loads to determine their 1RM, resting 3-5 minutes between trials. Up to five attempts will be used to identify the true 1RM (Schoenfeld et al., 2016).

Participants will stand in front of the triceps push-down machine, gripping the bar with a shoulder-width pronated grip. Throughout the exercise, the arms will be kept close to the torso, with the trunk slightly leaned forward, ensuring that the hands do not touch the body during full elbow extension. Participants will push the bar downward until reaching full elbow extension, then return to the starting position in a controlled manner; this will count as one repetition. The maximum load that each participant can successfully lift for one full repetition will be recorded as their 1RM (Hussain et al., 2020).

A calibrated hand grip dynamometer (Takei 5101, Tokyo, Japan) will be used to evaluate maximal hand grip strength. Participants will be instructed to grasp the dynamometer with their hand while exerting maximal isometric force, maintaining extended elbows and a neutral wrist position at the lateral side of the body. The testing protocol will include two trials with a 60-second rest interval between them. The highest value obtained will be recorded as the maximal force output. Throughout the test, participants will be strongly encouraged to exert maximal effort (Lopes-Silva et al., 2022).

The Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) test will be used to assess intermittent endurance capacity (Krustrup et al., 2003). Participants will complete 20 m shuttle runs at progressively increasing speeds, with 10 seconds of active recovery (light jogging over 2 m × 5 m) between runs. The test will stop when the participant can no longer maintain the required pace or fails to reach the line on time for two consecutive shuttles. Performance will be scored by the total distance (number of completed shuttles). A familiarization trial will be conducted before testing. The Yo-Yo IR1 demonstrates high reliability (ICC = 0.94; CV = 3.6%) (Krustrup et al., 2003).

Muscle thickness and cross-sectional area (CSA) will be measured 48-72 hours after the final training session, with no prior physical activity. A blinded physician will conduct all assessments using standardized anatomical points for the biceps brachii, triceps brachii, brachialis, anterior deltoid, upper trapezius, and rectus abdominis. Measurements will be taken in the axial plane with a light, 90° probe contact. A Toshiba Aplio 500 ultrasound device (10 MHz linear probe) will be used. CSA will be calculated by tracing the inner muscle border, and muscle thickness will be measured between superficial and deep aponeuroses. Two radiology specialists will evaluate the results jointly (Kubo et al., 2011).

Perceived Discomfort Level (PDL) will be assessed using a scale ranging from 0 ("no discomfort") to 10 ("maximum discomfort") (Borg, 1998). The PDL will be evaluated twice: once for overall body discomfort and once specifically for arm discomfort.

Exercise enjoyment will be measured using the shortened 8-item version of the Physical Activity Enjoyment Scale (PACES), originally developed by Kendzierski and DeCarlo (1991) and later adapted by Raedeke (2007). This single-factor scale evaluates the level of enjoyment experienced during exercise. Each item is rated on a 7-point Likert scale ranging from 1 ("do not enjoy at all") to 7 ("enjoy very much"), with 4 representing a neutral midpoint. Higher scores indicate greater enjoyment derived from the physical activity (Soylu et al., 2023).

The OMNI-RES resistance exercise scale will be used to assess participants' perceived exertion levels. A rating will be recorded at the end of each set, and the average of all set scores will be calculated and documented at the end of the exercise session. The scale will remain within the participant's visual field throughout the session, and they will be instructed to focus on their sense of effort immediately before each rating. Using standardized definitions and instructions, participants will rate their exertion on a scale ranging from 0 ("extremely easy") to 10 ("extremely hard") (Robertson et al., 2003).

Change in maximum volleyball serve speed (km/h) from baseline to 8-week follow-up measured by radar.

Change in Yo-Yo IR1 performance (VO2max) from baseline to 8-week follow-up.

Change in peak power and mean power (W and W·kg-¹) derived from the 30-s Wingate test from baseline to 8-week follow-up.

Change in session RPE (Borg 6-20 score), averaged across training sessions, from baseline to 8-week follow-up.

Change in perceived discomfort scores (0-10 scale) for whole body and arm-specific measures from baseline to 8-week follow-up.

Change in exercise enjoyment score (8-item PACES, score range 1-7) from baseline to 8-week follow-up.

Change in OMNI-RES average score (0-10) across sessions from baseline to 8-week follow-up.

Body mass index (BMI) (kg/m2) will asses by Inbody 270 (Biospace, California, USA).

Body fat percentage (%) will asses by Inbody 270 (Biospace, California, USA).