Capacitive Resistive Electric Transfer Therapy on Muscle Recovery

The Wingate test is used to determine power and anaerobic capacity (21). Each subject will perform the test: 30 seconds at maximum intensity interspersed with 1 minute of active recovery (pedaling 100 rpm), and this cycle will be repeated 3 times. The cycloergometer (Monark 818E, Vansbro, Sweden) will be used.

The test will be performed with a flywheel load resistance calculated based on 0.075 kg of the subject's current body weight. Heart rate during the test will be monitored with a heart rate monitor (Polar CS100 Cycling Heart Rate Monitor).

Near infrared spectroscopy (NIRS) monitoring detects changes in tissue oxygenation in small blood vessels, capillaries and oxygen transport (e.g. myoglobin). This instrument determines the relationship between oxyhemoglobin concentration and total hemoglobin concentration in the muscle. The sensors will be attached to the vastus lateralis and rectus femoris muscles during the Wingate test.

Ultrasound (US) images were used (US Aloka Prosound C3 15.4) with a high-frequency linear transducer (USTTL01, 12 L5), measured by a researcher with more than 10 years of experience handling the instrument. Measurements were taken in the muscle belly of the vastus lateralis (i.e., in the same location as the NIRS measurements) and the rectus femoris, with the patient lying on the examination table, knees fully extended, and legs without rotation. Ultrasound imaging was always performed at the same point (marked with a dermographic pen), with the linear transducer placed at the same angle (perpendicular to the skin). The 90º angulation of the transducer was verified before each measurement using a goniometer. The transducer was positioned without applying force to the skin, merely making contact with the ultrasound gel. Ultrasound device settings were adjusted for each patient to optimize the visualization of the target tissue, and the same settings were maintained for all measurements

before (at rest) and the day after (24h after the end of the Wingate test and recovery intervention), subject performed a 5s isometric maximal voluntary contraction to measure the maximal voluntary force of the knee extensor muscles. The force was registered in the dominant lower limb and the unit of measure was Newtons. A traction dynamometer (PCE Ibérica S.L., Albacete, Spain) was used. During the assessment, participants were seated with their hips and knees flexed at a 90o angle, and a strap was secured on the distal and anterior part of the dominant leg. The test was repeated three times, and the mean value was used for the analysis. Verbal encouragements were given throughout the contraction time.

muscle activity was recorded using surface electromyography from vastus lateralis and rectus femoris. The data was obtained by consists of three parts: (a) a Shimmer3 sEMG unit (Realtime Technologies Ltd., Dublin, Ireland). The signal was smoothed using a window size of 0.025s root mean square (RMS) and an overlapping of 0.0125s between windows. The Maximal Voluntary Isometric Contraction (MVIC) was calculated using the peak of the RMS signal during the extension knee isometric test. The RMS was the principal variable recorded for muscle activity. The participants' skin was cleaned with alcohol and dried before the electrodes were placed. If hair impeded the correct adhesion of the electrodes to the skin, the particular site was shaved. Self-adhesive 5×5 cm Valutrode® surface electrodes were placed on the muscle bellies according to the SENIAM project recommendations and with an interelectrode distance of 20 mm. Vastus lateralis electrodes were placed between the line from