Quadriceps and Hamstring Activation Timing

Quadriceps and Hamstring Activation Timing During Functional Tasks Following ACL Reconstruction

The anterior cruciate ligament (ACL) plays a crucial role in maintaining knee stability and enabling dynamic movement. ACL injuries are common, especially among athletes, and reconstruction surgery is frequently performed to restore knee function. Despite rehabilitation, neuromuscular deficits-particularly in muscle activation timing-may persist. This study will aim to evaluate the activation timing of quadriceps and hamstring muscles during a functional task in individuals who have undergone ACL reconstruction.

Study Overview

• Status: Enrolling by invitation
• Conditions: Anterior Cruciate Ligament Reconstruction; Knee Injury; Neuromuscular Control
• Intervention / Treatment: Diagnostic test: Electromyography

Detailed Description

This study will be conducted as a cross-sectional, quantitative investigation involving male participants who have undergone ACL reconstruction using semitendinosus and gracilis tendon grafts. Electromyographic (EMG) signals will be collected using the Noraxon Ultium EMG system and analyzed with Noraxon MyoResearch XP software. Muscle activation onset timing will be assessed for the vastus medialis oblique (VMO), vastus lateralis (VL), semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF). Participants will perform a standardized single-leg squat task, during which EMG-based activation timing will be recorded. The findings are expected to provide insight into neuromuscular control strategies and inform rehabilitation approaches following ACL reconstruction.

• Study Type: Observational
• Enrollment (Estimated): 25

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Karatay
    • Konya, Karatay, Turkey (Türkiye), 42030
      • KTO Karatay University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population will consist of male individuals aged 18-45 years who have undergone anterior cruciate ligament (ACL) reconstruction using semitendinosus and gracilis tendon grafts.

Description

Inclusion Criteria:

• participants must be males between 18 and 45 years old
• must have undergone ACL repair surgery and be within 6 months to 2 years post-surgery
• should have completed a standard rehabilitation program post-surgery
• must provide written informed consent to participate in the study
• should be in generally good health, without any other significant medical conditions that could affect the study outcomes;
• must have returned to a moderate level of physical activity post-surgery

Exclusion Criteria:

• participants with any neurological disorders affecting lower limb function or any other musculoskeletal disorders or injuries that could affect the lower limb, apart from the ACL injury
• those with cardiovascular conditions that contraindicate participation in physical activity
• those with contraindications to kinesiological electromyography, such as skin conditions or allergies to electrodes
• those who are unable or unwilling to comply with study procedures and follow-ups
• those who have had multiple ACL surgeries on the same knee
• participants involved in ongoing litigation related to their ACL injury

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Electromyography	Muscle Activation Timing (%MVIC)	Single session (approximately 15-20 minutes per participant)

Collaborators and Investigators

• Sponsor: KTO Karatay University

Study record dates

Study Major Dates

• Study Start (Estimated): April 20, 2026
• Primary Completion (Estimated): May 2, 2026
• Study Completion (Estimated): May 15, 2026

Study Registration Dates

• First Submitted: April 9, 2026
• First Submitted That Met QC Criteria: April 9, 2026
• First Posted (Actual): April 16, 2026

Study Record Updates

• Last Update Posted (Actual): April 16, 2026
• Last Update Submitted That Met QC Criteria: April 9, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Rehabilitation; Muscle activation; Electromyography; ACL reconstruction; Neuromuscular training
• Additional Relevant MeSH Terms: Wounds and Injuries; Leg Injuries; Knee Injuries; Diagnostic Techniques and Procedures; Diagnosis; Electrodiagnosis; Myography; Electromyography
• Other Study ID Numbers: 2025/029

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared to protect participant privacy and confidentiality.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No