## Materials and Methods
### Procedures
#### Elastic Band Training Exercises  
Six specifically tailored elastic band training exercises were performed targeting the neck and shoulder muscles. The choice of exercises was evidence-based and designed by an interdisciplinary team, including sports exercise training specialists, physical therapists, medical doctors, and chiropractors. The exercises were performed with a head harness (Neck Flex \({}^{\circledR}\), Leesburg, VA, USA) while using different color-coded elastic resistance bands (Thera-Band\({}^{\circledR}\), The Hygenic Corporation, Akron, OH, USA). The individual exercises are briefly presented below, as a detailed description can be found in an earlier publication [14] and video material is available online: Neck exercises.  
In short the exercises are the following:  
Figure 1: Bilateral electrode placement above the upper trapezius muscle (mUTR) and upper neck extensors muscles (mUNE) (**A**) and sternocleidomastoideus muscles (mSCM) (**B**).  
1. Shrugs (SH) were performed in standing position with the elastic band fixated under the feet and arms placed along the side of the body and shoulders relaxed. The head was held in an anatomically neutral position with eyes looking straight forward. During the exercise, shoulders were elevated as high as possible toward the ears against resistance and lowered again.
2. Reverse Flyes (RF) were performed seated with the elastic band fixated under the feet and with a straight back. Participants were instructed to position their head in an anatomically neutral position, lean the trunk forward (\(\sim\)20-30\({}^{\circ}\)), and place both arms pointing towards the floor. Elbows were kept in a static and slightly flexed position (\(\sim\)5\({}^{\circ}\)). During the exercise, both of the arms were raised toward a horizontal level against resistance and lowered again.
3. Cervical Extension (CE) was performed seated. The participants were instructed to keep a straight back, position their head in an anatomically neutral position, and lean the trunk forward (\(\sim\)20-30\({}^{\circ}\)). Arms were held strait with the hands placed underneath the knees. An elastic band was stretched between the hands and front of the head harness. The exercise was performed with a low cervical spine flexion, followed by a low cervical spine extension (against resistance).
4. Cervical Flexion (CF) was performed in the same way as during cervical extension, but the elastic band was stretched between a door anchor and the back of the head harness. During the exercise, the participants performed a low cervical spine flexion (against resistance), followed by a low cervical spine extension.
5. Cervical Lateral flexion (CL) was performed standing erect with the head in an anatomically neutral position. One hand was placed horizontally against a wall and an elastic band was stretched between the hand and side of the head harness. The exercise was performed with a low lateral spine flexion against resistance, followed by a low lateral spine extension. The exercise was performed for the right and left side, respectively.
6. Cervical rotation (CR) was performed seated with a straight back and trunk leaned forward (\(\sim\)20\({}^{\circ}\)). The head was held in an anatomically neutral position and rotated approximately 45\({}^{\circ}\) to either the right or left side. An elastic band was stretched between the head harness and a door anchor. Keeping a static upper body, the hips were flexed and the body flexed (against resistance), followed by an extension. The exercise was performed to the right and left side.