Omega-3 Fatty Acids in Muscle Function and Health

Muscle strength of the knee extensors will be measured using an isokinetic dynamometer during maximal voluntary contractions. The unit of measure is Newton-meters (Nm).

VO₂ max will be assessed during a graded exercise test on a cycle ergometer. The measure unit is milliliters per kilogram of body mass per minute (ml/kg/min).

MFI will be calculated as the percentage decline (%) in peak torque across a series of repeated maximal contractions of the knee extensor muscles on an isokinetic dynamometer.

Muscle oxygenation will be measured in the vastus lateralis using near-infrared spectroscopy (NIRS). Parameters include oxyhemoglobin (O₂Hb), deoxyhemoglobin (HHb), and total hemoglobin levels, which will be expressed in arbitrary units (AU).

Creatine kinase activity will be measured in International Units (IU) via the enzymatic colorimetric method in fasting plasma samples.

ROM of the knee joint will be measured in degrees (°) using an isokinetic dynamometer, with full extension defined as 0° and flexion recorded up to 120°.

Muscle thickness of the vastus lateralis will be measured using B-mode ultrasound with a linear probe, in millimeters (mm).

Echo intensity of the vastus lateralis will be assessed using B-mode ultrasound with a linear probe and quantified from grayscale image analysis, expressed in arbitrary units (0-255).

Fasting blood samples will be collected and analyzed to assess the participant's lipid profile, including: Total Cholesterol (TC). Expressed in mg/dL. Low-Density Lipoprotein Cholesterol (LDL-C). Expressed in mg/dL. High-Density Lipoprotein Cholesterol (HDL-C). Expressed in mg/dL. Triglycerides (TG). Expressed in mg/dL. Blood will be drawn after a minimum of 8-12 hours of fasting. Lipid concentrations will be determined using standard enzymatic colorimetric methods on an automated clinical chemistry analyzer.

The Omega-3 Index will be assessed as a biomarker of long-chain omega-3 fatty acid status. It is defined as the combined percentage (%) of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in red blood cell (RBC) membranes, expressed as a proportion of total identified fatty acids.

Blood samples will be collected following an overnight fast, and red blood cells will be isolated for fatty acid analysis. EPA and DHA levels will be quantified via gas chromatography, and the Omega-3 Index will be reported as a percentage (%).

RFD will be calculated as the slope of the torque-time curve during the early phase of voluntary contraction. It will be measured in Newton-meters per second (Nm/s).

EMD will be defined as the time lag between the onset of electrical activity (via surface EMG) and the onset of force production, measured in milliseconds (ms).

FME will be assessed during a submaximal isometric contraction using an isokinetic dynamometer and expressed as the percentage difference between the target and produced force (%).

JPS will be evaluated as the absolute angular difference between a target knee joint angle and the participant's reproduced angle, measured in degrees (°) using an isokinetic dynamometer.

DOMS will be assessed using a 1-10 visual analog scale (VAS), where 1 indicates no pain and 10 indicates extreme pain.

CMJ will be measured in centimeters (CM) using a force plate.

Duration of foot contact with the force plate during landing, expressed in milliseconds (ms).

The stability index will be assessed from the center of pressure displacement using a force platform and expressed in millimeters (mm).

F2-Isoprostanes will be quantified as a marker of lipid peroxidation using ELISA and expressed in picograms per milliliter (pg/mL).

Glutathione will be measured as an indicator of endogenous antioxidant capacity using a colorimetric assay and expressed in micromoles per gram of hemoglobin (μmol/g Hb).

Protein carbonyls will be measured as a marker of oxidative protein damage using a spectrophotometric assay and expressed in nanomoles per gram of hemoglobin (nmol/g Hb).

IL-6 will be measured as a marker of inflammation using ELISA and expressed in picograms per milliliter (pg/mL).

TNF-α will be measured as a marker of inflammation using ELISA and expressed in picograms per milliliter (pg/mL).

The pennation angle of the vastus lateralis will be measured under resting conditions using longitudinal B-mode ultrasound imaging and expressed in degrees (°).

Fascicle length of the vastus lateralis will be determined under resting condition from B-mode ultrasound images, either measured directly from visible fascicles or estimated using trigonometric calculations, and expressed in millimeters

Muscle stiffness, reflecting the resistance of the muscle to an external force, will be measured and expressed in newtons per meter (N/m) using the Myoton Pro device.

Muscle tone will be assessed using the Myoton Pro device, representing the natural oscillation frequency of the muscle at rest, and expressed in hertz (Hz).

Mechanical stress relaxation time will be assessed using the Myoton Pro device, representing the time required for the muscle to return to its original shape after a mechanical impulse, and expressed in milliseconds (ms).

Central and peripheral systolic and diastolic blood pressure will be measured using the SphygmoCor system and expressed in millimeters of mercury (mmHg).

Arterial stiffness will be assessed using the SphygmoCor system by measuring carotid-femoral pulse wave velocity (PWV), expressed in meters per second (m/s).