# The Acute Influence of Whole-Body Cryotherapy on Electromyographic Signals and Jumping Tasks
## 2 Materials and Methods
### Method
#### 2.3.2 Data Analysis  
Three vertical jump tests (each vertical jump test comprised three jumps) were performed: before WBC, after 1 min of WBC, and after 3 min of WBC. The examined individuals performed three CMJs at one-minute intervals. The CMJ jump test was conducted with hands on hips and to the maximum height possible. A BTS G-SENSOR inertia measurement instrument (BTS Bioengineering Corp., Quincy, MA, USA) was used to assess selected variables that characterize vertical jumps. The inertia sensor was attached to the S1 height using a dedicated strap. The device was equipped with a three-axis accelerometer with an option of sensitivity change (\(+-2\)G, \(+-4\)G), a three-axis gyroscope with an option of sensitivity change (\(+-300\) o/s, \(+-1200\) o/s), and a three-axis magnetic field sensor. Accelerometer records acceleration in three axes (vertical, anterior-posterior, and medial-lateral). The G-Sensor has been found valid for the assessment of physical activity in healthy adults with an inter-instrument correlation coefficient of between 0.90 and 0.99 and an intra-instrument coefficient variation of \(\leq\)2.5% [13,20,21]. The baseline data were converted to numeric units in one axis or as a size of a complex vector (namely the sum of the sizes of all three \begin{table}
\begin{tabular}{c c} \hline \hline
**Characteristics** & **(Mean \(\pm\) SD)** \\ \hline Age (years) & 27.9 \(\pm\) 7.9 \\ \hline Body mass (kg) & 77.9 \(\pm\) 8.8 \\ \hline Height (cm) & 181 \(\pm\) 6 \\ \hline Limb domination & 23 right/1 left \\ \hline This circumference (cm) & 54 \(\pm\) 4.7 \\ \hline Shank circumference (cm) & 38.9 \(\pm\) 3.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Group characteristics. axes). Complex vector data, used for recording selected variables that characterize the vertical jump, were used in the research. G-Studio version 3.0.18.0 software was used (BTS Bioengineering Corp., Quincy, MA, USA) to assess the parameters of the vertical jump. CMJ is divided into weighing, unweighting, braking, propulsion, flight, landing, and corresponding parameters. The following were measured: maximum height--the maximum movement of the center of gravity (COG) (cm); maximum velocity--maximum velocity COG in the jump before flight/feet getting off the ground (m/s); take-off and landing force--the force needed to take off and to land (N); maximum concentric force--maximum force at the concentric phase (kW); elasticity--(\(K\)) is the ratio of the value of the cause of the strain (\(\Delta F\)) to a quantitative measure of strain (\(\Delta L\)) [22]. \[K=\frac{\Delta F}{\Delta L} \tag{1}\]  
Surface electromyography (sEMG) is an experimental technique associated with obtaining, recording, and analyzing myographic signals. SEMG measurements were conducted using NeuroTrac(r) MyoPlus4 Pro (Verity Medical Ltd., Braishfield, UK), with 2 channels along with surface electrodes. The specification of the device fulfills the requirements as set out in ISEK and SENIAM publications. SEMG data were bandpass--filtered between 50 and 1000 Hz (finite impulse response (FIR) filter), rectified, and smoothed using a root-mean-square (RMS) value of 50 ms. The starting position for the measurement was seated on a chair with the knee and hip joints flexed at 90\({}^{\circ}\). After identification of belly muscle and completing all necessary preparations of the body (the skin around the rectus femoris was shaved and cleaned with alcohol), measurement of bioelectrical activity of the rectus femoris at rest and during isometric activity was conducted: The extension of the knee joint was flexed at 90\({}^{\circ}\), with the shank in a fixed position; electrodes were positioned on the fibula head and the distal part of the straight thigh muscle as recommended by the SENIAM protocol. SEMG activity results are shown in percentages due to performing the maximum voluntary contraction (MVC) trial of the rectus femoris muscle on the dominant limb of each examined participant.