## 2 Materials and Methods
### Procedures  
#### 2.3.1 Procedure in the H-Station  
Participants were tested in an H-station (FysioMeter, Aalborg, Denmark) using a standard Nintendo WBB (Nintendo, Kyoto, Japan) connected to a standard PC. Initially, participants performed a short quadriceps-specific warm-up followed by the isometric quadriceps strength test (Quad-H). Then, they undertook a short hamming-specific warm  
Figure 1: Flowchart of recruitment and testing order of participants. One participant was excluded due to a lower extremity injury not related to their participation in the current study. ID: isokinetic dynamometer.  
up before the isometric hamstring strength test (Ham-H). The warm-up consisted of four isometric sub-maximal followed by one maximal contraction, in accordance to procedures in previous studies [24; 25; 26]. Besides improving performance and preventing injuries, the warm-up also served the purpose of familiarizing the participants to the tests. Following warm-up, the participants had two minutes of rest before the test to minimize the potential effect of fatigue.  
For the Quad-H test, participants were seated on a standard treatment table with their hips flexed approximately at 85 degrees. The thigh was secured to the treatment table with two Velcro(r) straps placed at both proximal and distal part of the thigh (Figure 2a). The H-station was then placed as close to the participant as possible, and participants were instructed to place the tip of their shoe touching the marked center of the WBB. Then, the tester adjusted the height of the treatment table to align the sole of the shoe parallel to the floor. The height of the treatment table and knee angle, measured with a goniometer, were noted and reproduced for the second testing occasion. To secure that the H-station did not move during testing, a weight plate of 25 kg was placed in front of the H-station with the tester standing on the weight plate and securing both the top and bottom of the H-station (Figure 2a). The Quad-H test consisted of three sets of one isometric maximal knee extension, with one minute of rest between each set. Participants were instructed to keep their arms crossed over their shoulders and to push \"as fast and hard as possible\" with their toes and to hold the contraction for 3 s. Before the Ham-H test, a two-minute rest period was given to the participants.  
For the Ham-H test, the H-station was rotated 180 degrees horizontal to the treatment table (Figure 2b). Thereby, the WBB was positioned posterior to the participant's feet and the dominant knee of the participant was touching the knee padding of the H-station. The participant's thigh was secured using two straps, similar to the Quad-H test. The Ham-H test followed the same procedure as the Quad-H test, except participants were instructed to perform a knee flexion.  
For both the Quad-H- and the Ham-H test, verbal encouragement, and real-time visual biofeedback of the force trace were provided to ensure maximum effort during each repetition [27]. The trial was repeated if a counter movement was detected to ensure a  
Figure 2: Experimental setup for the quadriceps strength test (Quad-H) and hamstring strength test (Ham-H) in the H-station. (**a**) General setup for the Quad-H test with a 25 kg weight plate and tester securing the H-station during testing. (**b**) General setup for the Ham-H test.  
contraction starting from rest, or if one of the three repetitions varied with more than 20% from maximum peak value.  
Force data were collected via one Nintendo WBB with four strain gauge transducers positioned at each of the four corners. Data from the H-station were sampled at 100 Hz from each transducer and were transferred via Bluetooth to FysioMeter's software version 5.0.1 on a tablet. Subsequently, FysioMeter software filtered data by using a 4 th-order Butterworth lowpass filter with a cutoff frequency of 20 Hz. The FysioMeter software calculates one variable: absolute maximum force measured in kg.