## 2 Materials and Methods
### Procedure  
This study aimed to examine the effect of an acute bout of pyometric stimulus (RCMJ-30) applied with varying recovery intervals on unilateral CMJ performance and postural sway in national-level female volleyball players. A one-group repeated measures (pretest-posttest) design was employed. Data collection occurred during the official competition period in October 2023. Before starting the data collection, the team coaches and athletes were individually briefed on the study procedures. Written informed consent was obtained from all participants who met the study's inclusion criteria. These athletes then completeda one-week familiarization period, which involved repetitive vertical jump and unilateral exercises (single-leg jump and stance) to reduce potential learning effects.  
During the data-collection process, demographic and anthropometric characteristics were recorded first. On the same day, baseline measurements of the CMJ and postural sway for both the dominant and non-dominant legs were completed. On subsequent measurement days, athletes underwent unilateral CMJ and postural sway assessments following different recovery intervals of 2, 4, 6, and 8 min (i.e., R2, R4, R6, and R8), after the PAPE protocol. Before the conditioning activity to induce PAPE, all participants performed a standardized 10 min warm-up consisting of stretching and mobility exercises targeting the major muscle groups of the lower limbs [37]. Recovery intervals (in minutes) were randomized for each participant using a computerized random number generator (Microsoft(r) Excel) and administered in a non-sequential order. Unilateral CMJ and postural sway measurements were each performed as a single valid repetition, strictly adhering to the recovery intervals following the RCMJ-30. All participants (\(n=24\)) completed every stage of the study, including the familiarization period and all measurement sessions for unilateral CMJ and postural sway. The entire measurement process was completed over two weeks, with at least 48 h between each measurement day. The experimental design is presented in Figure 1.  
Unilateral CMJ and postural sway performances were measured using a force plate (Kistler, Winterthur, Switzerland, model: 9260 AA6, sampling rate: \(\approx\)400 Hz, size: 600 \(\times\) 500 \(\times\) 50 mm) positioned on a flat, hard surface. During the measurements, signals from the force plate were transmitted to a personal laptop via a data acquisition system (model 5691A; Winterthur, Switzerland; USB 2.0). The data for unilateral CMJ and postural sway performances were then processed using commercial software (Kistler's Measurement, Analysis, and Reporting Software, Kistler MARS, v4.0.2.99, S2P Ltd., Ljubljana, Slovenia), integrated with the force plate, and the results were exported to an Excel file [38].  
Environmental factors, including light, temperature, and ground conditions for the force plate, were standardized to ensure consistency in the assessments. All measurements were conducted within the same time window (2-4 p.m.) to minimize potential physiological changes related to circadian rhythms. Athletes were instructed to follow their usual  
Figure 1: Experimental design.  
nutrition programs on measurement days and were also advised to avoid heavy exercise in the 24 h preceding the measurement.