# Muscle Activity of Superimposed Vibration in Suspended Kneeling Rollout
## 2 Materials and Methods
### Procedures  
A familiarisation session was held one week before the data collection session (Figure 1) at the same time of day. This began with an explanation of the exercise and a subsequent reading of the informed consent form by the research team to ensure understanding, which was then signed by the participant. Subsequently, the participants' age, height, weight, and leg length (defined as the distance between the anterosuperior iliac spine and the medial malleolus of the tibia) were recorded. Additionally, the volume of weekly activity, experience with the use of suspension training, and both injury history and any medical contraindications were enquired about. Furthermore, upper-limb dominance was established as the arm that throws a ball at maximum speed. Finally, two sets of five repetitions of the suspended kneeling rollout were performed for each of the three conditions (non-vibration, vibration at 25 Hz, and vibration at 40 Hz), and the necessary corrections were made to ensure that all sets were performed with the correct technique. On the day of data collection, electrodes (Biopac EL504 disposable Ag-AgCl) were placed in the pectoralis (sternalis and clavicularis), anterior deltoid, serratus anterior, latissimus dorsi, and infraspinatus of the dominant arm [34]. Before this, the participants' skin was cleaned with 96% alcohol and shaved if necessary for the correct placement of the electrodes. Each pair of electrodes was placed at a distance of two centimetres and a reference electrode was placed on top of the iliac crest, following the SENIAM guidelines [35]. Subsequently, a standardised warm-up began with two sets of ten repetitions of the chest fly, two sets of fifteen internal shoulder rotations with an ABD of 90\({}^{\circ}\) and elbow flexion of 90\({}^{\circ}\), two sets of twenty pulses with an ABD of 120\({}^{\circ}\) and elbow flexion of 60\({}^{\circ}\), and finally two times of performing a 30 s plank. MVIC tests were then performed for each analysed muscle. Subsequently, the surface electromyography (sEMG) signal was normalised for the pectoralis (sternalis and clavicularis), anterior deltoid, serratus anterior, latissimus dorsi, and infraspinatus. While the participants performed a set of five repetitions of the suspended kneeling rollout under vibration and non-vibration conditions, the activation of the aforementioned muscles were registered. The exercise trials were conducted in random order and a 2 min rest period was provided to avoid fatigue between conditions (no vibration, vibration at 25 Hz, and vibration at 40 Hz). The vibration frequencies were established following the recommendations of [PERSON] and associates [36] for WBV and similar procedures in precedent studies [20; 21]. Furthermore, [PERSON] and associates [37] stated that the activity of several muscles was enhanced at frequencies from 20 Hz to 45 Hz. The suspended kneeling rollout pace was standardised at 40 beats per minute (bpm) using a metronome (Pro Metronome application, version 3.13.2; EUM Lab-Xannin Technology Gmbh, Hangzhou, China). After each exercise condition, participants were asked to complete the OMNI-Res scale. Suspended kneeling rollout was performed following the recommendations of [PERSON] [5] (Figure 2). The starting position of the exercise was adjusted according to the length of each participant's leg. Thus, the height of the suspension straps (TRX Suspension Trainer; Fitness Anywhere, San Francisco, CA, USA) and the distance from the knees to the suspension device were both set to 40% of the leg length. The TRX(r) was placed perpendicular to the ground in the starting position. The participant must lean the body forward without separating the handles, grabbing with the hands in a prone position, and holding the extension in the elbow until touching a pike situated at 140% of the leg length from the knees. The body must be aligned from the head to the knees throughout the entire run.