How Eccentric Closed Chain Training Affects Knee Strength and Muscle Properties in Soccer Players

University of Americas

Status: Completed

Conditions: Healthy

Treatments: Other: Field-based closed kinetic chain exercise with progressively increased time under tension; Other: Regular soccer training routines

Study type: Interventional

Funder types: Other

Identifiers

NCT06987344

2025015

Details and patient eligibility

About

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

Full 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.

Enrollment: 24 patients

Sex: Male

Ages: 18 to 25 years old

Volunteers: Accepts Healthy Volunteers

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.

Trial design

Primary purpose: Basic Science

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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24 participants in 2 patient groups

Active Control Group

Active Comparator group

Description:

Maintained their customary daily activities and regular soccer training routines: Trained three times a week, two days were dedicated to functional and tactical on-field training, while the third day was reserved for a two-hour gym session focused on flexibility, muscular strength, and endurance development.

Treatment:

Other: Regular soccer training routines

Closed Kinetic Chain Group

Experimental group

Description:

In addition to the same activities as the active cotrol group, participants performed five to seven different closed kinetic chain drills during the two days of field-based training, completing two to three sets per drill and eight to fourteen repetitions per set. The training volume underwent gradual increments over the course of every week. The total training volume for externally loaded CKC exercises was calculated by summing sets × repetitions × load (kg), yielding a cumulative volume of approximately 10,863 kg over 12 sessions. For exercises involving bodyweight or elastic resistance, training volume was estimated using time under tension (TUT), computed as the product of repetitions and eccentric phase duration. The cumulative TUT throughout the 6-week protocol amounted to 9,300 seconds (155 minutes) of eccentric loading.

Treatment:

Other: Regular soccer training routines

Other: Field-based closed kinetic chain exercise with progressively increased time under tension