# Changes in Joint Power and Energetics during a Sport-Specific Jumping Fatigue Protocol
## 2 Materials and Methods
### Procedures  
For the study, participants were required to perform repetitive standing countermovement squat jumps, which were defined as follows: starting from an erect position, a downward movement is performed by flexing the knee and hip joint, and then the knee and hip joint are rapidly extended [17]. The goal of the countermovement jump was for the athlete to reach as high on the Vertec jump height measurement system (Sports Imports, Hilliard, OH, USA)--used to determine the athletes' vertical jump and reach height--as possible. Prior to testing, athletes performed a self-selected warmup and performed submaximal practice countermovement squat jumps as described above. During these practice jumps, each athlete became accustomed to the jumping protocol and the use of the Vertec jump system.  
Following the warmup, each athlete performed maximum effort countermovement squat jumps every twenty seconds until they were fatigued. This protocol was based on the study by [PERSON] et al. (1987) [18], wherein it was determined that volleyball players perform high intensity activities every 24-44 s during gameplay. The rest time between jumps (20 s) employed in this study was selected because it was the shortest time between trials in which the data could be recorded and the Vertec jump meter could be reset.  
For the purposes of this investigation, an athlete was classified as fatigued it they met one of the following criteria:  
1. The athlete could no longer maintain 88% of their maximum jump heights for three consecutive jumps (failure jumps). This was determined through pilot testing, where participants performed the jump protocol and verbally quantified their level of fatigue.
2. The athlete verbally stated they were fatigued and no longer wished to continue jumping.  
During each jump of the fatiguing protocol, kinetic ground reaction force data were collected on the right leg at 2400 Hz via a force platform embedded in the lab floor (Kistler AG, Winterthur, Switzerland) while kinematic data of the right foot, lower leg, upper leg and sacrum were recorded using an 8-camera motion capture system capturing images at 240 Hz (Motion Analysis Corp., Rohnert Park, CA, USA). The motion capture system was calibrated to an accuracy defined by a 3D residual below 0.6 mm. The foot, shank, thigh, and hips were defined by attaching retro-reflective markers measuring 19 mm in diameter to each segment using double-sided tape, with three markers attached per segment in the following locations: fibula, upper tibial crest, distal lateral leg to define the shank segment, posterior shoe heel, distal shoe heel, lateral shoe heel to define the rearfoot segment, lower lateral thigh, upper lateral thigh and anterior thigh to define the thigh segment and left/right anterior superior iliac spine, and left and right posterior superior iliac spine (Figure 1). The ankle, knee, and hip joint centers were determined using a standing neutral trial with additional markers placed on the medial and lateral malleolus (ankle), medial, and lateral epicondyles (knee) and greater trochanter. Joint centers were identified as the midpoint of the two joint markers for each joint. The participants were asked to stand with their feet hip-width apart and with their knee and hips fully extended. Prior to analysis, the kinematic and kinetic data were filtered using a low-pass, fourth-order Butterworth filter with a cut-off frequency of 15 Hz. The kinematic and kinetic data were analyzed first with Kintrak 7.0.25 software (Human Performance Laboratory, University of Calgary, Calgary, AB, Canada), which calculated the ankle, knee, and hip joint moment; angular velocity; joint power; and joint energetics, which were then imported into MATLAB (MathWorks, Natick, MA, USA) for further analysis (normalization of the fatigue protocol, etc.).