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IRCT20250905067129N1 IRCT 2025-09-15 Shahid Beheshti University Plyometric-jump training with unstable load UL-PJT = unstable loaded plyometric-jump training Plyometric-jump training with versus without unstable load to improve physical fitness in trained young volleyball players: a randomized controlled trial 2025-04-21 anticipated 30 Complete https://irct.ir/trial/86001 interventional Randomization: Randomized, Blinding: Single blinded, Placebo: Not used, Assignment: Parallel, Purpose: Supportive, Randomization description: In this study, the allocation of participants to groups was performed using a combined approach of pair-matching and simple randomization in order to both reduce baseline heterogeneity between groups and ensure true randomization. First, all participants were matched in pairs based on their baseline performance in the Jump-and-Reach test, so that individuals with similar jump ability were grouped together. This pair-matching procedure was applied to achieve a more balanced distribution of baseline jumping ability across groups. Within each pair, participants were then assigned to the study groups using simple randomization. The random sequence was generated with Microsoft Excel using the RAND() function. Each participant received a random number, and after sorting these numbers in ascending order, participants were allocated to one of the three study groups: 1.Unstable Load Plyometric Jump Training (UL-PJT), 2.Stable Plyometric Jump Training without additional load (S-PJT), and 3. Active Control (CON). The unit of randomization was individual-based. The randomization sequence was generated and kept by a researcher who was not involved in data collection or analysis. To maintain allocation concealment and prevent any potential selection bias, the randomization codes were placed in opaque, sealed, and sequentially numbered envelopes, which were opened only at the time of participant assignment. Thus, the randomization procedure in this trial ensured both a reduction in baseline heterogeneity across groups and the preservation of a truly random allocation process, Blinding description: This trial was conducted with a single-blind design. Participants were not informed about their group allocation or the specific differences between interventions. In addition, data analysis was performed by an independent statistical consultant who was blinded to group assignments. However, due to the nature of the intervention and the need for close supervision during exercise sessions and testing, the investigator responsible for conducting the interventions and outcome assessments was aware of group allocation. Therefore, blinding was ensured at the level of participants and data analysis, while assessor blinding was not feasible. N/A . Intervention 1: Intervention group1: Participants in this group performed plyometric jump training with an unstable load equivalent to 10% of their body weight over a 4-week period (three sessions per week, totaling 12 sessions). The unstable load was provided using a barbell and two water-filled gym balls. The exercises were conducted on the gym floor and consisted of consecutive jumps over obstacles with heights ranging from 35 to 50 cm. The intensity and volume of the training progressively increased, with the number of jumps rising from 48 repetitions in the first session to 104 repetitions in the final sessions. Each session lasted 15 to 25 minutes, with a work-to-rest ratio of 1:7 and a 2-minute rest interval between exercises. All sessions began with a RAMP warm-up protocol (light running, dynamic stretching, and submaximal jumps). Intervention 2: Intervention group2: This group followed the same training protocol as the UL-PJT group, with the exception that no unstable load was added to the exercises. Participants performed jump training on a stable surface without using water-filled gym balls. The number of sessions, duration of training, type of exercises, volume, intensity, and warm-up protocol were identical to those of the first group, ensuring that the only interventional variable was the presence or absence of an unstable load. Intervention 3: Control group: Participants in the control group continued their regular volleyball training over the 4-week period (three sessions per week, each approximately 90 minutes). Their training consisted of standard team technical and tactical activities, with no additional plyometric exercises or specific interventions. This group served as a comparison to determine the net effect of the plyometric interventions in the other two groups. No - There is not a plan to make this available Justification or reason for not sharing IPD is To adhere to ethical principles and protect participants' personal and confidential information, the raw data (individual participant data) from this study will not be shared for public use or secondary research. However, if required, and solely to assure journal reviewers or editors of the accuracy of statistical analyses, the data will be provided confidentially.
public Mohammad Fashi
Shahid Beheshti University, Shahid Shahriari Square, Daneshjo Blvd., Evin.
Tehran Iran (Islamic Republic of) 1983969411 +98 21 2990 5858 fashi84.u@gmail.com Shahid Beheshti University scientific Mohammad Fashi
Shahid Beheshti University, Shahid Shahriari Square, Daneshjo Blvd., Evin.
Tehran Iran (Islamic Republic of) 1983969411 +98 21 2990 5858 fashi84.u@gmail.com Shahid Beheshti University Iran (Islamic Republic of) At least 2 years of experience competing in Tehran volleyball school competitions or Tehran league competitions. Their specific sports training volume is ≥6 hours per week. Boys age range 14 to 18 years. No cardiovascular problems. Avoiding the use of stimulants and certain medications (steroids) No smoking or drinking alcohol. 14 years 18 years Male A history of acute or chronic musculoskeletal injury/disorders of the ankle, knees, or lower back. Training volume less than 6 hours per week. Age above 18 and below 14. History of cardiovascular disease and problems in the participant. Taking steroid medications. Tobacco and alcohol consumption. Experience of participating in competitions for more or less than 2 years. Other Other Other Intervention group1: Participants in this group performed plyometric jump training with an unstable load equivalent to 10% of their body weight over a 4-week period (three sessions per week, totaling 12 sessions). The unstable load was provided using a barbell and two water-filled gym balls. The exercises were conducted on the gym floor and consisted of consecutive jumps over obstacles with heights ranging from 35 to 50 cm. The intensity and volume of the training progressively increased, with the number of jumps rising from 48 repetitions in the first session to 104 repetitions in the final sessions. Each session lasted 15 to 25 minutes, with a work-to-rest ratio of 1:7 and a 2-minute rest interval between exercises. All sessions began with a RAMP warm-up protocol (light running, dynamic stretching, and submaximal jumps). Intervention group2: This group followed the same training protocol as the UL-PJT group, with the exception that no unstable load was added to the exercises. Participants performed jump training on a stable surface without using water-filled gym balls. The number of sessions, duration of training, type of exercises, volume, intensity, and warm-up protocol were identical to those of the first group, ensuring that the only interventional variable was the presence or absence of an unstable load. Control group: Participants in the control group continued their regular volleyball training over the 4-week period (three sessions per week, each approximately 90 minutes). Their training consisted of standard team technical and tactical activities, with no additional plyometric exercises or specific interventions. This group served as a comparison to determine the net effect of the plyometric interventions in the other two groups. Jump-and-reach height. Timepoint: 1. Initial measurement (pre-test) of jump and reach height in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: For J&R, standing reach height was initially assessed during upright erect standing with both feet in lateral position close to a wall, the dominant arm fully extended in upright direction and the fingers touch-ing a wall-mounted touch-sensitive sensor connected to a digital display (Sargent jump device, Danesh Salar Iranian, Iran). Subsequently, participants performed a countermovement (i.e., knee and hip flexion) with arm swing immediately followed by a rapid and powerful vertical jump. The participants’ task was to touch the wall-mounted scale during flight time at the highest position with their middle finger. Drop jump. Timepoint: 1. Initial measurement (pre-test) of drop jump in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: Drop jumps were performed with the participants stepping off a 40 cm box, landing on firm floor, and immediately jumping as high as possible. Participants were instructed to touch the wall-mounted scale during the flight at the highest position. Jump height was defined as the difference between standing reach height and jumping reach height. Knee flexion/extension peak isokinetic torque. Timepoint: 1. Initial measurement (pre-test) of Knee flexion/extension peak isokinetic torque in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: The Knee flexion/extension peak isokinetic torque in the dominant leg was measured using the Biodex Multi-Joint System 4 Pro (Biodex Medical System Inc., USA). Leg dominance was determined based on the lateral preference questionnaire. The device was calibrated before each test. Participants were seated with a hip joint angle of 80 degrees and secured with straps around the upper body and pelvis. The shank of the dominant leg was attached to the dynamometer lever to record the torque generated by the muscles. The knee joint range of motion was set between 10 and 100 degrees (0 degrees = full extension). The test consisted of three sets of five maximal knee flexion–extension movements at an angular velocity of 60 degrees/second. The rest interval between sets was 180 seconds. For the final analysis, the average of the three sets was calculated. Knee flexion/extension time to peak isokinetic torque. Timepoint: 1. Initial measurement (pre-test) of Knee flexion/extension time to peak isokinetic torque in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: The Knee flexion/extension time to peak isokinetic torque in the dominant leg was measured using the Biodex Multi-Joint System 4 Pro (Biodex Medical System Inc., USA). Leg dominance was determined based on the lateral preference questionnaire. The device was calibrated before each test. Participants were seated with a hip joint angle of 80 degrees and secured with straps around the upper body and pelvis. The shank of the dominant leg was attached to the dynamometer lever to record the torque generated by the muscles. The knee joint range of motion was set between 10 and 100 degrees (0 degrees = full extension). The test consisted of three sets of five maximal knee flexion–extension movements at an angular velocity of 60 degrees/second. The rest interval between sets was 180 seconds. For the final analysis, the average of the three sets was calculated. Knee flexion/extension power. Timepoint: 1. Initial measurement (pre-test) of Knee flexion/extension power in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: The Knee flexion/extension power in the dominant leg was measured using the Biodex Multi-Joint System 4 Pro (Biodex Medical System Inc., USA). Leg dominance was determined based on the lateral preference questionnaire. The device was calibrated before each test. Participants were seated with a hip joint angle of 80 degrees and secured with straps around the upper body and pelvis. The shank of the dominant leg was attached to the dynamometer lever to record the torque generated by the muscles. The knee joint range of motion was set between 10 and 100 degrees (0 degrees = full extension). The test consisted of three sets of five maximal knee flexion–extension movements at an angular velocity of 60 degrees/second. The rest interval between sets was 180 seconds. For the final analysis, the average of the three sets was calculated. Overall Stability Index. Timepoint: 1. Initial measurement (pre-test) of Overall Stability Index in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: Static bilateral balance was measured using the Biodex Balance System SD (Biodex Medical System Inc., USA). After necessary training by the tester, participants were asked to stand as still and stable as possible during the test. Each player performed three 20-second trials with a 10-second rest interval between trials. The test difficulty was set at a tilt level ranging from 8 to 5 (based on initial pilot results), with level 1 creating the highest degree of instability. Continuous visual feedback regarding the body's center of gravity was provided on the screen during the test. Ultimately, the Overall Stability Index was calculated, and the average of the three trials was used for the final analysis. Medial–Lateral Stability Index. Timepoint: 1. Initial measurement (pre-test) of Medial–Lateral Stability Index in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: Static bilateral balance was measured using the Biodex Balance System SD (Biodex Medical System Inc., USA). After necessary training by the tester, participants were asked to stand as still and stable as possible during the test. Each player performed three 20-second trials with a 10-second rest interval between trials. The test difficulty was set at a tilt level ranging from 8 to 5 (based on initial pilot results), with level 1 creating the highest degree of instability. Continuous visual feedback regarding the body's center of gravity was provided on the screen during the test. Ultimately, the Medial–Lateral Stability Index was calculated, and the average of the three trials was used for the final analysis. Anterior–Posterior Stability Index. Timepoint: 1. Initial measurement (pre-test) of Anterior–Posterior Stability Index in week zero, before the start of training.2. Final measurement (post-test) at the end of week four, 48 hours after the last training session. Method of measurement: Static bilateral balance was measured using the Biodex Balance System SD (Biodex Medical System Inc., USA). After necessary training by the tester, participants were asked to stand as still and stable as possible during the test. Each player performed three 20-second trials with a 10-second rest interval between trials. The test difficulty was set at a tilt level ranging from 8 to 5 (based on initial pilot results), with level 1 creating the highest degree of instability. Continuous visual feedback regarding the body's center of gravity was provided on the screen during the test. Ultimately, the Anterior–Posterior Stability Index was calculated, and the average of the three trials was used for the final analysis. Shahid Beheshti University Approved 2025-04-19 Research Ethics Committee of Shahid Beheshti University Ethics Committee in Biomedical Research, Shahid Beheshti University, Shahid Shahriari Square, Daneshjoo Boulevard, Evin. Tehran Tehran Iran (Islamic Republic of)