Purpose: This study aimed to examine the effects of different muscle warm-up phases on knee joint proprioception, vertical jump, agility, and balance in professional youth soccer players. Methods: Twenty-five professional youth football players under 18 were assessed during muscle rest, warm-up, and fatigue phases using tests measuring knee proprioception, dynamic balance, explosive power, and agility.
Purpose: The purpose of this study was to investigate how different phases of muscle warm-up affect knee joint proprioception, vertical jump performance, agility, and dynamic balance in professional youth soccer players. Understanding these effects is critical for optimizing warm-up protocols to enhance athletic performance and reduce injury risk in this population. Methods: Twenty-five male professional youth football players under the age of 18 (mean age 16.5 ± 1.2 years) were randomly selected for this study. Each participant underwent assessments during three distinct muscle states: resting, after warm-up, and post-training fatigue. Knee joint proprioception was evaluated at a 30° angle using a digital inclinometer to measure joint position sense accuracy. Dynamic balance was assessed through the Y-balance test in three directions: anterior, posteromedial, and posterolateral. Explosive power was measured using the Sargent vertical jump test, while agility was tested with the T-test. All measurements were performed in each muscle condition to compare performance across the different warm-up phases.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
25
All assessments will be measured in three warming phases of the muscle. The first phase is the Rest state (Cold state), which is the phase before the training begins. In this phase, the athlete has not warmed up. The second phase is the "Warming state," where the athlete has started the training and has warmed up for 20 minutes. The third phase is the "Post-Training Phase," which occurs 10 minutes after the completion of a 90-minute training session. Measurements will be taken for all three phases.
Nezahat Keleşoğlu Faculty of Health Sciences
Konya, Konya, Turkey (Türkiye)
Proprioception Test
Knee joint proprioception was assessed using a Baseline Digital Inclinometer (Fabrication Enterprises Inc., USA). Active joint position sense (JPS) of the dominant knee was measured with this device. Participants were seated in a 90° hip and knee flexion position. Initially, the researcher passively positioned the participant's knee at 30° of flexion with eyes open, instructing the participant to memorize the angle. The participant was then asked to close their eyes and actively replicate the target position. The angular deviation from the target was recorded as the proprioceptive error. This procedure was repeated three times, and the mean error was used for analysis .
Time frame: It was measured separately in all three phases of exercise. Baseline (resting phase), immediately after the warm-up phase, and immediately after the fatigue phase.
Sargent Vertical Jump Test
The Sargent Jump Test (SJT) was used to evaluate the explosive power of the lower extremities. Participants stood side-on to a wall and extended their dominant arm upward to mark their maximum reach height while standing flat-footed. This point was recorded as the baseline. From a standing position, participants performed a maximal vertical jump and touched the wall at the peak of their jump. The difference between the jump reach and the standing reach height was calculated and recorded as the jump height. Three trials were conducted, and the highest value was used for analysis. A higher score indicates better performance .
Time frame: It was measured separately in all three phases of exercise.Baseline (resting phase), immediately after the warm-up phase, and immediately after the fatigue phase.
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