Effects of manual massage and massage gun recovery techniques on muscle properties after countermovement jumps in healthy and physically active university students

The study will employ a randomized crossover design. All participants will undergo a total of four testing sessions. The first session will involve familiarization with the Bosco 60-second test, during which each participant will receive a detailed explanation and demonstration of the test procedure, followed by a correction of their technique. Between the first session involving familiarization and remaining three sessions there will be a period of ten days. The remaining three sessions will consist of a short standardised warm-up lasting 3 minutes, followed by a 5-minute rest period to avoid post-activation potentiation effects. This will be followed by initial testing of muscle contractile properties of the m. vastus medialis, one set of three countermovement jumps with a preparation phase and a one-minute rest period after them, the Bosco 60-second test, immediate testing of muscle contractile properties (assessed every 15 seconds over a 5-minute period for each leg), subjective load perception, and subjective muscle pain assessment. One of the recovery methods (manual massage, massage gun or control treatment - passive recovery) will then be applied, immediately followed by testing of muscle contractile properties and subjective muscle pain assessment. Ten minutes after each recovery technique muscle contractile properties will be tested and subjective muscle pain will be assessed. Finally, participants will perform another set of three countermovement jumps with preparation. Subjective muscle pain assessment will also be conducted 24 and 48 hours after the study protocol. During the application of each experimental recovery method, two different intervals will be used (3 and 6 minutes). The interval between testing sessions will be 10 days, with testing conducted at approximately the same time of day to avoid potential circadian rhythm effects. The initial session will take 30 minutes whilst the remaining three sessions will be approximately 1 hour each. To assess the contractile properties of the vastus medialis muscle, the TMG-100 device will be used in accordance with the manufacturer's instructions (TMG-BMC d.o.o., Ljubljana, Slovenia). Participants will lie in supine position, completely relaxed, with the tested leg positioned at a 150° angle at the knee joint. After electrode placement, the position of the electrodes will be marked to ensure standardized measurement. A sensor for collecting muscle contractile properties will be positioned between the electrodes. The electrical stimulus will be set to 20 mA with a duration of 1 ms, then progressively increased by 10 mA every 10 seconds. The parameters used in this study will include the radial displacement of muscle belly transverse fibers (Dm), contraction time (Tc), maintenance of contraction (Ts), muscle relaxation (Tr), and muscle contraction delay time (Td). The maximum height of the countermovement jump will be used as a sport-specific test to assess neuromuscular fatigue. This test was chosen due to its similarity to the fatigue-inducing protocol. Each participant will perform three countermovement jumps with hands placed on the hips, and the highest jump value will be recorded for analysis. Counter movement jump is a vertical jump and among the most often used tests for maximal anaerobic power output of the lower extremities. It is an eccentric-concentric muscle action which involves coordinated extension of the trunk, hip, knee and ankle. The initial position of the subject for the counter movement jump is an upright stance. It is important that the subject performs a quickly coupled counter movement – push-off action. While performing this lowest position should be a semi-squat (knee ~90° and trunk/hips in a flexed position) like in the case of the squat jump. The jump must be performed as quickly and explosively as possible in order to make the highest possible jump in the shortest possible time. 60-second Bosco protocol will be used for creating muscle fatigue. A large number of sports activities require the performance of multiple maximal vertical jumps, which is why this form of muscle fatigue induction was chosen. Studies often utilize the Bosco test lasting 15, 30, or 60 seconds. The 60-second Bosco protocol was selected because participants experience fatigue after 60 seconds of countermovement jumps, and this test is frequently used to determine anaerobic capacity. The 60-second Bosco test will consist of a single set of countermovement jumps, as described in Bosco, Luhtanen, and Komi (1983), conducted within two plates of the Optogait device (Version 1.6.4.0, Microgate, Bolzano, Italy; number of optical sensors: 96; sampling rate: 1000 Hz; surface area: 600 cm x 100 cm). During the Bosco 60-second test, participants will stand in place with their hands on their hips and feet shoulder-width apart. Following a signal from the examiner, the participant will squat to a self-selected depth and then perform countermovement jumps continuously for 60 seconds. The parameters assessed in this study will include ground contact time, flight time, jump height, cadence, reactive strength index, power, verticality, and mechanical jump power. Recovery techniques which will be used include manual massage, massage gun and control treatment - passive recovery. The manual massage techniques used in this study will include effleurage, friction, and kneading. All three massage movements will be applied to both muscles by an experienced physiotherapist with extensive expertise in manual massage. During the session, a combination of all three techniques will be performed, with one leg receiving 60 seconds of effleurage followed immediately by 60 seconds of friction and then 60 seconds of kneading, resulting in a total duration of 3 minutes. The same techniques, in the same order, will be applied to the other leg, but each technique will last 120 seconds, for a total duration of 6 minutes. Participants will provide feedback on massage intensity on a scale of 1 to 10, using a subjective assessment method during the treatment (Garcia-Sillero, 2021). For massage gun therapy, the Hypervolt high-frequency vibration device will be used, commonly applied for recovery in sports. It will be used by a physiotherapist. The frequency will be set to 2100 Hz. Therapy will be conducted by following the muscle fibers of m. vastus medialis with the device for 3 minutes on one leg and 6 minutes on the other leg. During use, participants will provide feedback on pressure intensity on a scale of 1 to 10 (Garcia-Sillero, 2021). The order of recovery methods (type of recovery and time interval on left vs. right leg) will be randomly allocated. Each participant will undergo different recovery methods in the three sessions which will be randomly allocated using a computerised procedure. For the subjective load assessment sRPE (Session Rate of Perceived Exertion) will be used. After jumping set, each participant will rate the intensity of the training on a scale from 0 to 10, where 0 represents rest and 10 represents maximal exertion (Foster et al., 2001). The Visual Analogue Scale (VAS) will be used to assess muscle pain, with 0 indicating no pain and 10 representing the maximum pain (Alexander, 2007). To monitor adherence to the intervention session attendance checklists will be used.