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. The aim of the study is to monitor and evaluate the physiological changes produced by ACL injury on muscle performance using non-invasive near-infrared spectroscopy (NIRS) devices in trained athletes. This descriptive cross-sectional observational multicentre multicentre study, with Balearic Islands ethics committee IB 5585/24PI, will include males aged 18-65 years who have undergone ACL surgery, divided into 3 groups that: have an evolution of less than 6 months (ACL1), more than 2 years since the surgical intervention and are already practising normal physical-sports activities (ACL2) and the control group (CON) that has never suffered an ACL affectation to date. The 3 groups will perform an incremental intervallic test (4:1) on a cycloergometer or treadmill (according to the specificity of their sport), where different muscular haemodynamic variables will be assessed using 12-24 NIRS devices. The main study variables will be the muscular haemodynamic values of each muscle analysed and their correlation between them: muscular oxygen saturation, absolute capillary haemoglobin, loaded and unloaded with oxygen and relative muscular haemoglobin blood flow, loaded and unloaded with oxygen. Secondary variables will be heart rate, socio-demographic variables (age, toxic habits, injury and sports history) and subjective perception of effort (RPE-20).
An adipose layer of <2 cm in areas of NIRS placement, assessed with a plicometer
Understand written, read and spoken Spanish, English or Catalan.
Having any cardio-metabolic, hormonal, neurological or other comorbidities that could affect participation in the study (e.g. severe mental illness, end-stage disease).
Regular athlete with training and/or competition >3 days/wk prior to injury.
ACL injury <6 months after surgery.
Able to perform an incremental intervallic test on a cycloergometer or treadmill.
The sample, which will be selected by convenience, will be made up of participants who have a diagnosis of ACL involvement and who have undergone surgery (total or partial), either recently or have had an injury in previous years, may be recruited to participate in the study. Healthy, physically active patients who have never had an ACL injury will also be recruited. The sample will initially come from the Físic Espai de Salut Integral, Centre Re3MOVE, MET Salut, Hospital Universitari Son Espases (HUSE) and San Juan de Déu Palma-Inca centres. Other private and public physiotherapy, rehabilitation and recovery centres, as well as private entities (clubs, federations, associations and organisations) that may contain participants susceptible to being included in the study, are expected to be included as they are accepted by the respective research commissions.
Case-control
Cross-sectional
Physical fitness test: Progressive intervalic test
Other interventionAn incremental interval test of 4\' of work for 1\' of rest will be performed at an individual intensity below the aerobic threshold. At the end of the rest minute, the load shall be increased slightly. In order to be as adjusted and individualised as possible, the subjective physical condition level stated by the patient during the sociodemographic data collection shall be taken as a reference for the establishment of the initial load, being a value of power (W) in cycle ergometer and speed (km/h) in treadmill. Never less than 50W or 6 km/h, respectively. The minimum incremental values will be 25W or 0.5km/h until you are unable to complete a full interval. An incomplete interval shall also be recorded and analysed. During the one minute rest period, as will have been well emphasised during the explanation of the test, no part of the body may be moved at all, so at the end of the 4 minutes of work, the evaluator will count down for the patient to get ready and remain stil
Muscular Oxygen Saturation (SmO2 - %)
Percentage of haemoglobin + myoglobin at muscle capillary level loaded with oxygen
Absolute Capillary Haemoglobin (ThB - g/dL)
grams of haemoglobin + myoglobin loaded and unloaded with oxygen divided by decilitres of blood taken up by the devices in the muscle capillaries
Oxygen-loaded capillary haemoglobin (O2HHb - g/dL)
grams of haemoglobin + oxygen-loaded myoglobin divided by the decilitres of blood taken up by the devices in the muscle capillaries
Capillary Haemoglobin Oxygen Depleted (HHb - g/dL)
grams of haemoglobin + oxygen-loaded myoglobin divided by the decilitres of blood taken up by the devices in the muscle capillaries
Heart Rate (ppm)
will be monitored at all times through the use of a heart rate monitoring strap (Garmin HRM-ProTm Plus) which will transmit the constants via Bluetooth to the head unit.
Subjective perception of effort (RPE-20)
Central and local (leg) fatigue shall be assessed just before the start of the test, at the rest period of each interval, at the end of the test and at 1 and 3 minutes after the end of the test. Data shall be recorded directly into the storage software using the Borg scale.
Anthropometry and adiposity indicators: height
height (m)
Anthropometry and adiposity indicators: weight
weight (kg). In addition to height, BMI (kg/m2) will also be taken.body mass index (BMI) (kg/m2)
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