Clinical trial NCT06987344: How Eccentric Closed Chain Training Affects Knee Strength and Muscle Properties in Soccer Players
Official title: Field-based Closed Kinetic Chain Training With Progressive Eccentric Time Under Tension: Effects on Knee Strength and Lower Limb Viscoelasticity in Soccer Players: a Randomized Controlled Trial
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Healthy
Keywords: Exercise therapy
Muscle strength
Lower extremity
Tendons
Lead sponsor: University of Americas
Sponsor class: OTHER
First posted: 2025-05-23
Enrollment: 24
Sex: MALE
Minimum age (years): 18
Maximum age (years): 25
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: BASIC_SCIENCE

Brief summary: The goal of this study is to learn whether a 6-week lower-body training program using closed kinetic chain (CKC) exercises with slow, controlled movements (called "eccentric time under tension") can improve leg muscle strength and muscle-tendon viscoelastic properties in male university soccer players.

The Main Questions Are:

1. Does this type of training improve knee strength?
2. Does it change the way muscles and tendons respond to movement or pressure?

What Will Participants Do?

1. Join one of two groups: one does the CKC training program, the other continues regular soccer training
2. Train twice a week for 6 weeks
3. Have their leg strength tested using special equipment
4. Have their muscle and tendon properties measured with a handheld device

Detailed description: This randomized controlled trial investigated the effects of a 6-week, field-based closed kinetic chain (CKC) exercise program with progressively increased eccentric time under tension (TUT) on isokinetic knee performance and lower limb muscle-tendon viscoelastic properties in male university soccer players.

A total of 24 healthy participants were randomly assigned (1:1) to either an intervention group performing supervised CKC exercises or an active control group that maintained routine soccer training. The CKC training was performed twice per week and included progressive increases in eccentric phase duration and external loading. Training volume was quantified using both mechanical load and eccentric TUT. Each session lasted approximately 35 minutes and included a variety of multi-joint, bilateral and unilateral exercises performed on a soccer field.

Baseline and post-intervention assessments were conducted using:

Isokinetic dynamometry (Biodex System 3 Pro) to measure concentric peak torque, mean power, and agonist/antagonist ratio at 60°/s.

MyotonPRO handheld myotonometer to assess oscillation frequency and stiffness of specific lower limb muscles (VM, VL, ST, GM) and tendons (Achilles, patellar).

Muscle and tendon assessments were performed following standardized anatomical landmarks. To ensure data reliability, repeated trials were used and measurements with high variability were repeated. Pre-testing familiarization was implemented to reduce learning effects.

The statistical approach included a two-way repeated measures ANOVA to compare group (CKC vs. control) and time (pre vs. post) effects. Holm-Sidak post hoc tests were applied when appropriate, and effect sizes were interpreted using eta squared (η²). All data analyses were conducted using JASP software (v0.18.3).

The protocol was reviewed and approved by an institutional ethics committee , and written informed consent was obtained from all participants. No serious adverse events were reported, and dropout was minimal (n = 4). No dietary interventions were applied; however, participants were instructed to maintain consistent routines throughout.

Eligibility criteria: Inclusion Criteria:

* Absence of any medical conditions that could compromise their ability to participate.
* Active membership in their university's soccer team for a minimum of one year.

Exclusion Criteria:

* Musculoskeletal injuries reported in the two months prior to the start of the study.
* Surgical interventions involving the lower limbs within the past year.

Primary outcomes:
measure: Change from baseline in the rotational peak torque relative to body mass at 6 weeks
timeFrame: From enrollment to the end of closed kinetic chain training protocol at 6 weeks
measure: Change from baseline in the rotational mean power at 6 weeks
timeFrame: From enrollment to the end of closed kinetic chain training protocol at 6 weeks
Secondary outcomes:
measure: Change from baseline in the agonist/antagonist strength ratio at 6 weeks
timeFrame: From enrollment to the end of closed kinetic chain training protocol at 6 weeks
measure: Change from Baseline in the muscle oscillation frequency at 6 weeks
timeFrame: From enrollment to the end of closed kinetic chain training protocol at 6 weeks
measure: Change from Baseline in the stiffness at 6 weeks
timeFrame: From enrollment to the end of closed kinetic chain training protocol at 6 weeks
Other outcomes:
Locations:
city: Viña del Mar
country: Chile
facility: Human Movement Analysis Laboratory
state: V región/Valparaíso
Study officials:
References: