The main goal of this randomized controlled trial (RCT) is to evaluate the chronic effects of using instep weights on technical, physical (conditional), and perceptual parameters in amateur male soccer players. The secondary objective will be to propose a training methodology using instep weights to enhance athletic performance. The following hypotheses are formulated based on the objectives outlined previously. Hypothesis 1: the use of instep weights will enhance performance in ball striking speed, change of direction ability, and repeated sprint capacity. Hypothesis 2: the use of instep weights will negatively affect performance in ball striking accuracy and ball control. Hypothesis 3: the use of instep weights will not produce adverse effects on perceived exertion, groin pain or reduce maximal adductor, quadriceps and hamstring muscle contraction values.
A RCT will be performed and players will be randomly assigned in one of the two groups (experimental or control). Players will attend their regular training sessions and the protocol will be divided into two phases: * Phase 1: familiarization On the recruitment day, players will be briefed on the study procedures, followed by the reading and signing of informed consent forms. Familiarization with the study procedures will take place over the two weeks prior to the intervention phase. During this period, participants will practice all testing protocols once a week and will wear 100-gram instep weights in different training sessions. * Phase 2: intervention During the intervention phase, all players who meet the inclusion and exclusion criteria will be recruited and will be randomly allocated into an intervention group (experimental) or a non-intervention group (control group). Randomization will be conducted by an external researcher using blocked randomization via a web-based tool (Urbinak, 1997). Both groups will undergo distinct interventions over an 8-week period. The study will be conducted during the competitive season on artificial turf field under consistent environmental conditions. Players will wear soccer boots for all testing procedures. Testing will occur at three time points: * Pre-intervention: first day of Week 1 to collect baseline data. * Mid-intervention: first day of Week 5. * Post-intervention: first day of Week 9.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
42
Players will perform their scheduled training sessions while wearing a 150-gram instep weight. The use of instep weights in the intervention group will be introduced progressively and gradually, increasing both the frequency of sessions and the duration of their use. During weeks 1-2, instep weights will be used in one training session per week. During weeks 3-5, will be used in two training sessions per week. And during weeks 6-8, will be used in three training sessions per week. The duration of instep weight usage within each session will increase by 5% weekly, starting at 40% in Week 1 and reaching 75% by Week 8.
University of Vic-Central University of Catalonia
Vic, Spain
Hip and Groin Outcome Score (HAGOS)
The HAGOS was first described and validated in 2011 in the British Journal of Sports Medicine (Thorborg et al., 2011). It reliably assesses a patient's perception of disability, discomfort, or issues related to the hip and/or groin region. In addition to perceived dysfunction, the questionnaire also measures actual disability. HAGOS was designed to evaluate both short-term functional changes, such as those observed week-to-week during therapy, and long-term outcomes, such as the natural progression of a condition. HAGOS consists of six subscales scored from 0 (extreme) to 100 (no existance) hip/groin problems. Scales evaluate: Symptoms; Pain ; Physical Function in Daily Living; Function in Sports and Recreation; Participation in Physical Activities and Quality of Life. With: 7, 10, 5, 8, 2 and 5 items for each subscale respectively. The final measure is a composite outcome measure obtained by summing the values of the 6 subscales
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Subjective perceptual well-being questionnaire measures change: RPE
Rate of Perceived Exertion (RPE) using the Borg (Borg, 1982) 0-10 scale (being 0 no exertion and 10 maximal exertion) will also be recorded. Players will respond one simple question: How hard was your session? Each player will complete the 0-to-10 scale without the presence of other players and will not see the values of other participants. Players will be allowed to mark a plus sign (interpreted as 0.5 point) alongside the integer value
Time frame: The questionnaire will be administered within the first 15-20 minutes following the conclusion of each training session.
Ball Striking Accuracy Test
A precision screen (Nagasawa et al., 2011) measuring 7.3 meters wide by 2.4 meters high will be used to delineate target zones on a regulation football goal. The screen will have four openings (target zones) located in the top corners (Zones A and B) and bottom corners (Zones C and D). Each opening measures 1.5 meters wide by 0.8 meters high. Players will perform two strikes for each target zone in the following sequence: A, B, C, D. Accuracy will be assessed manually. A strike will score a point if the ball passes through the designated opening. Each successful strike scores one point, with a maximum total score of eight points (two successful strikes per zone). Accuracy will also be analyzed by high zones (A and B), low zones (C and D), and individual zones. Participants will be instructed to strike the ball with maximum power and precision. Official match balls used by the team for training and competition will be utilized, inflated to a pressure of 0.6-0.8 bar.
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Ball Striking Velocity Test
A Radar Stalker ATS II (Stalker®, USA) will be used to record ball velocity. Offering a time precision of 0.01 seconds, a velocity range of 1-1432.3 km/h, and the ability to detect ball motion up to 152.40 meters. Measurements will record the ball's speed in meters per second (m/s) as validated by previous studies (Ferraz et al., 2012; Tomas et al., 2014). The radar will be positioned directly behind the goal, 15 meters from the ball. The striking point will be at the penalty spot, 11 meters from the goal line. Participants will be instructed to strike the ball with maximum power and precision. Immediate feedback on velocity will be provided after each strike to encourage performance consistency or improvement. Official match balls used by the team for training and competition will be utilized, inflated to a pressure of 0.6-0.8 bar. Velocity data will be recorded (km/h) automatically by the radar.
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Change of Direction (COD) and Ball Control
The test evaluates the player's ability to change direction quickly and efficiently, as well as to control the ball while doing so. To evaluate these variables, the modified Barrow test (Bidaurrazaga et al., 2015) will be used. Players will start the test by positioning the foot they use most efficiently to begin the sprint at the starting point. They will then begin the test voluntarily, without waiting for a starting signal. The test will be performed in two conditions: without a ball and with a ball. Each player will perform the test twice in each condition, and the average result will be recorded. Results will be recorded using ChronoJump Boscosystem® photogates (Barcelona, Spain), with timing measurements conducted using Chronopic and recorded through Chronojump software version 2.2.1. Players will complete the test two times without the ball and two times with the ball, with a 2-minute rest between each attempt. The average values (sec) will be considered and analyzed.
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Repeated Sprint Ability (RSA)
To replicate the extreme demands of competition in terms of the number, duration, and recovery of sprints, a valid and reliable test (Aziz et al., 2008; Gabbett, 2010) will be used. This test aims to assess the ability of players to repeatedly perform high-intensity sprints with minimal recovery, reflecting the demands placed on athletes during competition. The test will consist of 6-8 sprints of 20 meters each, performed at maximal effort, with 20-second cycles between sprints. After each sprint, players will perform a 10-meter decelerationfollowed by a 10-meter active recovery (jogging). Results will be recorded using ChronoJump Boscosystem® photogates(Barcelona, Spain). The time measurements will be taken using Chronopic and recorded through Chronojump software version 2.2.1. The average values (sec) will be considered and analyzed.
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Adductors Maximum Voluntary Contraction (MVC)
MVC test will be used to assess the maximum force exerted by the hip adductors. A Lafayette Manual Muscle Testing System(Lafayette Instrument Company, Lafayette IN, USA) will be used to measure the muscle force. Two different procedures will be used to test the hip adductors(Esteve et al., 2018): 1. Short Lever Test: resistance will be placed between the knees while the feet are positioned on the examination table. The hip will be in 45-degree flexion. 2. Long Lever Test: resistance will be placed between the ankles, with the hip in neutral position (0° flexion). The maximum isometric force (Newtons;N) will be recorded as the average value of three attempts. For the hip adductor tests, both body mass and the length of the short and long levers (distance in cm between the body's center of mass and the point of resistance) will be measured for each player. Force values will then be normalized based on body weight and lever lengths and reported as N·m/kg.
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Knee extensors Maximum Voluntary Contraction (MVC)
The MVC test will be used to assess the maximum force exerted by the quadriceps. This is a valid and reliable test for evaluating the force capacity of the knee extensors (Alshahrani et al., 2023; Mentiplay et al., 2015). A Lafayette Manual Muscle Testing System(Lafayette Instrument Company, Lafayette IN, USA) will be used to measure the muscle force. To assess the quadriceps (knee extensors), the participant will be seated with the hips and knees flexed at 90°. The dynamometer will be placed on the anterior aspect of the lower leg, just proximal to the ankle joint (Alshahrani et al., 2023; Mentiplay et al., 2015). The maximum isometric force (measured in Newtons, N) will be recorded as the average value of three attempts. For the quadriceps test, the average force (N) from the three attempts will be normalized by body mass (measured in N/kg).
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Knee flexors Maximum Voluntary Contraction (MVC)
The MVC test will be used to assess the maximum force exerted by the hamstrings. This is a valid and reliable test for evaluating the force capacity of the knee flexors (Alshahrani et al., 2023; Mentiplay et al., 2015). A Lafayette Manual Muscle Testing System(Lafayette Instrument Company, Lafayette IN, USA) will be used to measure the muscle force. To assess the hamstrings (knee flexors), the participant will also be seated with the hips and knees flexed at 90°. The dynamometer will be positioned on the posterior aspect of the lower leg, proximal to the ankle joint (Alshahrani et al., 2023; Mentiplay et al., 2015). The maximum isometric force (measured in Newtons, N) will be recorded as the average value of three attempts. For the hamstring test, the average force (N) from the three attempts will be normalized by body mass (measured in N/kg).
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
Body mass
Players body mass in kg will be measured
Time frame: Pre-intervention (first day of week 1), mid-intervention (first day of week 5), and post-intervention (first day of week 9)
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