A Paradigm Shift in Musculoskeletal Rehabilitation Assessment After ACL Reconstruction Using Near-Infrared Spectroscopy (HemoNIRS-LCA)

A Paradigm Shift in the Assessment of Musculoskeletal Rehabilitation After Anterior Cruciate Ligament Reconstruction: Protocol for a Multicenter Case-Control Cross-Sectional Study Using Near-Infrared Spectroscopy (HemoNIRS-LCA)

This study aims to establish and compare muscle haemodynamic response patterns in physically active subjects with anterior cruciate ligament (ACL) reconstruction, at different time points after surgery, against healthy controls, using 24 non-invasive near-infrared spectroscopy (NIRS) devices simultaneously during a single incremental interval cycling test.

Muscle haemodynamics has so far been assessed using at most 2-3 near-infrared spectroscopy devices on isolated muscles and without correlating variables. At the same time, research on musculoskeletal pathologies is limited, and there are no studies that analyse the haemodynamic changes that occur when the anterior cruciate ligament (ACL) is injured and whether these changes last over time.

This is a multicentre, observational, case-control, cross-sectional study, approved by the Clinical Research Ethics Committee of the Arnau de Vilanova University Hospital (CEIC-3203), that will include males aged 18-65 years who have undergone ACL reconstruction, divided into three groups: less than 6 months since surgery (ACL1), more than 2 years since surgery with normalised physical activity (ACL2), and a healthy control group with no history of ACL injury. Recruitment has not yet started and is expected to begin in October 2026

Study Overview

• Status: Not yet recruiting
• Conditions: Exercise; Anterior Cruciate Ligament Reconstruction; Hemodynamics; ACL Injury; Oxygen Consumption Based Assessment of Hemodynamics
• Intervention / Treatment: Diagnostic test: Incremental Interval Test on a Cycle Ergometer

Detailed Description

Assessment of muscle haemodynamics after musculoskeletal injury has traditionally relied on a limited number of near-infrared spectroscopy (NIRS) sensors placed on isolated muscles, without a simultaneous, multi-site approach. This study addresses that methodological gap in the context of anterior cruciate ligament (ACL) reconstruction.

This study aims to establish and compare muscle haemodynamic response patterns, measured using NIRS, in physically active individuals with ACL reconstruction at different time points after surgery, compared with healthy controls.

It is a multicentre, observational, case-control, cross-sectional study, conducted in three groups of males aged 18 to 65 years: ACL1 (less than 6 months since ACL reconstruction), ACL2 (more than 2 years since ACL reconstruction, with normalised physical activity and no longer undergoing rehabilitation), and a healthy control group with no history of ACL injury.

Each participant completes a single incremental interval cycling test on a cycle ergometer. During the test, 24 portable NIRS devices (Moxy) simultaneously and bilaterally record haemodynamic data at 12 muscle locations: rectus femoris (proximal and distal thirds), vastus medialis, vastus lateralis, biceps femoris (proximal and distal thirds), semitendinosus, gluteus maximus, tibialis anterior, gastrocnemius, medial deltoid, and biceps brachii; combining propulsive, stabilising, and postural musculature and reflecting a multi-joint, whole-body approach to the assessment of exercise-induced muscle haemodynamics.. Data are analysed using a proprietary multiparametric interpretation algorithm designed to evaluate the haemodynamic performance of multiple muscle groups simultaneously and comparatively. Assessors and statisticians remain blinded to group assignment throughout data collection and analysis.

Primary outcomes are muscle oxygen saturation, capillary haemoglobin concentration, and muscle blood flow, recorded continuously via NIRS at each of the 12 bilateral locations during exercise and through 2 to 3 minutes of post-exercise recovery (an individually variable recovery period). Secondary outcomes include heart rate (continuous Bluetooth monitoring), rating of perceived exertion (Borg CR-10 scale, 0-10), anthropometric and adiposity indicators (height, weight and body mass index), sociodemographic and clinical variables (age, toxic habits, injury and sports history, and physical activity in the preceding 48 to 72 hours), and study dropouts with their reason.

Sample size was calculated using G-Power, based on a moderate effect size (Cohen's d = 0.5) estimated from a study in the process of publication, with a 95% confidence level (Z = 1.96), 80% statistical power (β = 0.20), and a 10% non-response rate, yielding a required sample of 43 participants per group (total n = 129).

The study is conducted at four collaborating centers: Espai Físic de Salut Integral, Fisioplanet, Hospital Universitari Son Espases (HUSE), and Sant Joan de Déu Palma-Inca (SJD). It is approved by the Clinical Research Ethics Committee of the Arnau de Vilanova University Hospital (CEIC-3203)

• Study Type: Observational
• Enrollment (Estimated): 129

Contacts and Locations

• Study Contact: Name: Francisco J. Verdejo-Amengual; Phone Number: +34 670729376; Email: xisco.verdejo@udl.cat
• Study Contact Backup: Name: Oriol Martínez-Navarro, PhD; Phone Number: +34 619562618; Email: oriol.martinez@udl.cat

Study Locations

• Spain
  • Balearic Islands
    • Palma de Mallorca, Balearic Islands, Spain, 07015
      • Espai Físic de Salut Integral (Sant Agustí)
      • Contact: Francisco J Verdejo-Amengual; Phone Number: +34 973702459; Email: xisco.verdejo@udl.cat
      • Principal Investigator: Francisco J Verdejo-Amengual
      • Sub-Investigator: Claudia Arumí-Trujillo
      • Sub-Investigator: Oriol Martínez-Navarro, PhD
      • Sub-Investigator: Fran Valenzuela-Pascual, PhD
      • Sub-Investigator: Joan Llobera Morro

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Participants are recruited from four collaborating centres in Mallorca: Espai Físic de Salut Integral, Fisioplanet, Hospital Universitari Son Espases (HUSE), and Sant Joan de Déu Palma-Inca (SJD), coordinated by the Universitat de Lleida (UdL). The sample is a non-probability convenience sample of men aged 18 to 65 years, allocated to three groups. LCA1: recent post-surgical ACL reconstruction, up to 6 months since surgery, referred by the physiotherapist or rehabilitation physician responsible for their recovery. LCA2: long-term post-surgical ACL reconstruction, at least 2 years since surgery, currently physically active, identified retrospectively from clinical databases at the collaborating centres. CON: healthy controls with no history of ACL or meniscal injury, recruited among people attending the collaborating centres for general fitness training, who are also regularly physically active.

Description

General inclusion criteria

• Men aged 18 to 65 years.
• Adipose tissue thickness of less than 2 cm at the NIRS device placement sites, assessed with a skinfold calliper.
• Functional capacity to complete an incremental interval test on a cycle ergometer.
• Able to understand and communicate, both orally and in writing, in Spanish, Catalan or English.

General exclusion criteria

• Cardiometabolic, endocrine, neurological, or other severe comorbidity that could compromise participant safety, alter physical performance, or interfere with the interpretation of the results.
• Disabling pain preventing completion of the physical assessment as established in the protocol.

Eligibility criteria (LCA1 group)

• Physically active before the injury, with an exercise frequency greater than 3 days per week.
• Surgically treated with ACL reconstruction.
• Time since surgery of 6 months or less.
• Explicit authorisation from the physiotherapist or rehabilitation physician responsible for their recovery, confirming that the participant is able to safely tolerate the physical demands of the test.

Eligibility criteria (LCA2 group)

• History of ACL reconstruction surgery, with a minimum of 2 years since the intervention.
• Regular physical exercise practice (more than 3 days per week) during at least the 2 to 3 months prior to assessment.

Eligibility criteria (CON group)

• Regular physical exercise practice (more than 3 days per week) during at least the 2 to 3 months prior to assessment.
• No history of ACL injury or meniscal injury in either knee.

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
LCA1; Participants who underwent ACL surgical reconstruction no more than 6 months before assessment and are at a stage of recovery that allows them to safely perform and tolerate the physical test.	Diagnostic test: Incremental Interval Test on a Cycle Ergometer; Participants perform a single incremental interval test on a cycle ergometer: 4 minutes of exercise followed by 1 minute of rest, at an individual intensity below the anaerobic threshold. All participants begin at the same initial load of 50 watts, increased at the end of each rest minute in steps of 25 watts, until the participant is unable to complete a full interval; this final incomplete interval is also recorded and analysed. During the rest minute, participants must remain completely still, without moving any part of the body; at the end of each 4-minute work period, the assessor counts down so the participant can prepare for the next interval. Throughout the test, 24 near-infrared spectroscopy (NIRS) devices are placed bilaterally over 12 muscle sites: rectus femoris (proximal and distal thirds), vastus medialis, vastus lateralis, biceps femoris (proximal and distal thirds), semitendinosus, gluteus maximus, tibialis anterior, gastrocnemius, medial deltoid, and biceps brachii.; Other Names: Fitness assessment test; Physical test
LCA2; Participants with a history of ACL surgical reconstruction at least 2 years before assessment, who have maintained regular physical activity, are no longer undergoing rehabilitation, and are able to perform and tolerate the same physical test as the LCA1 group	Diagnostic test: Incremental Interval Test on a Cycle Ergometer; Participants perform a single incremental interval test on a cycle ergometer: 4 minutes of exercise followed by 1 minute of rest, at an individual intensity below the anaerobic threshold. All participants begin at the same initial load of 50 watts, increased at the end of each rest minute in steps of 25 watts, until the participant is unable to complete a full interval; this final incomplete interval is also recorded and analysed. During the rest minute, participants must remain completely still, without moving any part of the body; at the end of each 4-minute work period, the assessor counts down so the participant can prepare for the next interval. Throughout the test, 24 near-infrared spectroscopy (NIRS) devices are placed bilaterally over 12 muscle sites: rectus femoris (proximal and distal thirds), vastus medialis, vastus lateralis, biceps femoris (proximal and distal thirds), semitendinosus, gluteus maximus, tibialis anterior, gastrocnemius, medial deltoid, and biceps brachii.; Other Names: Fitness assessment test; Physical test
CON; Healthy participants with no history of ACL or meniscal injury, matched by regular physical activity to the other study groups, and able to perform and tolerate the same physical test as the LCA1 group	Diagnostic test: Incremental Interval Test on a Cycle Ergometer; Participants perform a single incremental interval test on a cycle ergometer: 4 minutes of exercise followed by 1 minute of rest, at an individual intensity below the anaerobic threshold. All participants begin at the same initial load of 50 watts, increased at the end of each rest minute in steps of 25 watts, until the participant is unable to complete a full interval; this final incomplete interval is also recorded and analysed. During the rest minute, participants must remain completely still, without moving any part of the body; at the end of each 4-minute work period, the assessor counts down so the participant can prepare for the next interval. Throughout the test, 24 near-infrared spectroscopy (NIRS) devices are placed bilaterally over 12 muscle sites: rectus femoris (proximal and distal thirds), vastus medialis, vastus lateralis, biceps femoris (proximal and distal thirds), semitendinosus, gluteus maximus, tibialis anterior, gastrocnemius, medial deltoid, and biceps brachii.; Other Names: Fitness assessment test; Physical test

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Muscular Oxygen Saturation (SmO2 - %)	Percentage of oxygen-loaded haemoglobin and myoglobin at the muscular capillary level, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minu
Absolute Capillary Haemoglobin (ThB - g/dL)	Grams of oxygen-loaded and oxygen-depleted haemoglobin and myoglobin per deciliter of blood captured by the devices at the muscular capillary level, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics.
Oxygen-loaded capillary haemoglobin (O2HHb - g/dL)	Grams of oxygen-loaded haemoglobin and myoglobin per decilitre of blood captured by the devices at the muscular capillary level, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics.
Capillary Haemoglobin Oxygen Depleted (HHb - g/dL)	Grams of oxygen-depleted haemoglobin and myoglobin per decilitre of blood captured by the devices at the muscular capillary level, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics
Blood Flow of Relative Muscle Haemoglobin (ThB BF - g/dL/min)	Relative blood flow value of haemoglobin per unit of time circulating through the muscular capillary, calculated by incorporating heart rate values, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics
Blood Flow of Oxygen Loaded Relative Muscle Haemoglobin (O2HHb BF - g/dL/min)	Relative blood flow value of oxygen-loaded haemoglobin per unit of time circulating through the muscular capillary, calculated by incorporating heart rate values, recorded via NIRS at 0.5-second intervals.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics
Blood Flow of Oxygen Discharged Relative Muscle Haemoglobin (HHb BF - g/dL/min)	Relative blood flow value of oxygen-depleted haemoglobin per unit of time circulating through the muscular capillary, calculated by incorporating heart rate values, recorded via NIRS at 0.5-second intervals	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart Rate (bpm)	Continuous heart rate monitoring throughout the test and post-exercise recovery, using a chest strap heart rate monitor (Garmin HRM-Pro Plus) with Bluetooth transmission to the central data unit.	Continuously during the test and through a minimum 2-minute post-exercise recovery period, extended up to 3 minutes according to each participant's individual recovery kinetics
Rating of Perceived Exertion (RPE-10 / Borg CR-10 scale - 0-10)	Subjective perception of physical effort measured using the reduced Borg scale (CR-10), ranging from 0 (no exertion) to 10 (maximum exertion).	Recorded before the test, during the initial 5-minute calibration period; during the test, at the end of each 4-minute work interval; and immediately at the end of the test.
Anthropometry: Height (m)	Height measured with a standard stadiometer, used together with body weight to calculate body mass index (BMI, kg/m2).	Baseline, prior to the incremental interval cycling test, recorded once.
Anthropometry: Weight (kg)	Body weight (kg), measured together with height to calculate body mass index (BMI, kg/m2).	Baseline, prior to the incremental interval cycling test, recorded once.
Sociodemographic and Clinical Variables	Sociodemographic and clinical data collected via a brief questionnaire, including age, toxic habits, injury history, sports history, and physical activity in the preceding 48 to 72 hours.	Baseline, prior to the incremental interval cycling test, recorded once.

Collaborators and Investigators

• Sponsor: Universitat de Lleida
• Investigators: Study Director: Francesc Valenzuela-Pascual, PhD, Universitat de Lleida; Study Director: Oriol Martínez-Navarro, PhD, Universitat de Lleida

Study record dates

Study Major Dates

• Study Start (Estimated): October 1, 2026
• Primary Completion (Estimated): December 30, 2026
• Study Completion (Estimated): December 30, 2026

Study Registration Dates

• First Submitted: September 25, 2024
• First Submitted That Met QC Criteria: September 27, 2024
• First Posted (Actual): October 1, 2024

Study Record Updates

• Last Update Posted (Actual): September 10, 2026
• Last Update Submitted That Met QC Criteria: September 5, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: Exercise; Hemodynamics; Oxygen consumption; Spectroscopy, Near-Infrared; Case-Control Studies; Vascular resistance; Cross-Sectional Studies
• Additional Relevant MeSH Terms: Wounds and Injuries; Leg Injuries; Knee Injuries; Behavior; Anterior Cruciate Ligament Injuries; Motor Activity
• Other Study ID Numbers: HemoNIRS-LCA

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: The plan to share individual participant data (IPD) is pending a final decision, as data interpretation in this study relies on an algorithm that is the subject of an international patent (WO2022013479A9) held by a third party. This intellectual property matter constrains the scope of any future data-sharing plan. Once resolved, the research team will consider making anonymized hemodynamic and sociodemographic data available to qualified researchers upon reasonable request, subject to applicable data protection regulations (EU Regulation 2016/679 and Spanish Organic Law 3/2018).
• IPD Sharing Supporting Information Type: SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No