Cryotherapy on Muscle Function

The assessment of muscle mechanical properties will be performed using the MyotonPRO device. Measurements will be taken bilaterally from the quadriceps muscle, specifically targeting the knee extensors.

The isometric muscle strength of the participants' dominant quadriceps muscle will be measured using a dynamometer. Muscle strength assessments will be performed with a calibrated Lafayette dynamometer (model 01163; Lafayette Instrument Company, Lafayette, IN, USA). Participants will receive verbal instructions about the procedure prior to testing. During the assessment, care will be taken to ensure that the device does not slip, that appropriate force is applied, that no compensatory movements occur in the tested extremity or other body parts, and that weakness is not masked by body positioning. For knee extensor evaluation, participants will be seated with their hands crossed over their shoulders, hips flexed at 90°, and knees locked at 60° of extension.

The EMG activity of the participants' dominant quadriceps muscle will be measured using a surface electromyography (EMG) device. For this assessment, the NeuroTrac® MyoPlus 2 dual-channel EMG ETS device (Verity Medical Ltd., UK) will be used. The device will be connected to a computer via dedicated software. To measure muscle activity, 32 mm diameter, circular, adhesive silver-silver chloride (Ag-AgCl) electrodes will be used. Three electrodes will be prepared individually for each participant. Prior to placement, the skin area where the surface electrodes will be attached will be cleaned with an alcohol wipe to reduce skin impedance. A reference electrode will be placed on the leg to eliminate external interference, while the active electrodes will be positioned directly over the target muscle.

The pressure pain threshold (PPT) of the dominant quadriceps muscle will be assessed using a digital pressure algometer. The algometer is equipped with a flat circular rubber-tipped probe (1 cm²) and will be applied perpendicularly to the skin over the quadriceps muscle belly. The probe will be pressed gradually at a constant rate (approximately 1 kg/cm² per second) until the participant reports the sensation of pressure turning into pain. The corresponding force value will be recorded as the PPT. Each participant will receive verbal instructions prior to the test, and the measurement site will be marked to ensure consistency across repeated measures. The assessment will be performed in a seated and relaxed position, with care taken to avoid muscle contraction or movement during the measurement.