## 2 Materials and Methods
### Parameters Analyzed  
To evaluate the impact of the HIIT protocol on various physiological and psychological parameters, we employed a series of tests conducted before, during, and after the HIIT sessions. These tests were carefully selected to provide a comprehensive overview of the participants' performance and condition, ensuring a multifaceted understanding of the effects of acute physical fatigue. It is crucial to note that all the participants had previous experience with these tests, effectively minimizing the potential for a learning effect that could skew the results. This prior familiarity allows for more reliable assessments of changes attributable to the HIIT protocol itself rather than improvements in test performance due to repeated exposure. **Cardiovascular Response**: To assess the cardiovascular response to the HIIT protocol, we monitored participants' heart rate (HR) in real-time using a Polar V800 heart rate monitor, a sophisticated device known for its accuracy and reliability in capturing heart rate data. This device, manufactured by Polar Electro in Kempele, Finland, is specifically designed for sports and fitness research, offering precise heart rate measurements that are crucial for evaluating the intensity and effectiveness of the HIIT sessions. By analyzing these heart rate data, we could determine how participants' cardiovascular systems reacted to the stress of high-intensity exercise, providing valuable insights into their physical condition and endurance capabilities [30]. **Rate of Perceived Exertion (RPE)**: The subjective intensity of the training sessions was quantified using the Borg Scale, a widely recognized method for assessing perceived exertion. This scale ranges from 6 to 20 levels, where higher numbers correspond to higher levels of exertion [31]. The Borg Scale is an effective tool for measuring an individual's perception of exercise intensity, allowing for a subjective assessment that complements the objective physiological data collected. By employing this scale, we could gauge participants' subjective experiences of the HIIT protocol, offering a holistic view of its impact. **Upper Body Muscular Performance**: To evaluate the muscular performance of the upper body, we used a dynamometer to measure the maximum isometric contraction force of the dominant hand. This test, conducted with a device from [PERSON], Japan, is a standard measure of grip strength but also serves as an indicator of overall upper body strength. Participants were asked to perform the test twice, with the highest value recorded for analysis. This approach ensures accuracy and reliability in assessing the muscular endurance and strength gains from the HIIT sessions [32]. **Lower Body Muscular Performance**: Lower body muscular performance was assessed through a horizontal jump test, which is a simple yet effective measure of leg power and explosiveness. Participants were instructed to jump as far as possible with their hands placed on their waist to prevent the use of arm swing, thus focusing the assessment on leg strength. The test was performed twice, with the longest distance jumped recorded for analysis. This test provides a direct measure of the lower body's power, an essential component of overall athletic performance and a key indicator of the effectiveness of the HIIT protocol in enhancing muscular performance [30]. **Algometer Test**: To evaluate the pain threshold, the algometer test was meticulously conducted on the anterior border of the upper trapezius muscle, both pre- and post-test and among all participants, adhering to a standardized procedure [33]. Pressure was consistently increased at a controlled pace of 1 kg/sec. Participants were instructed to signal the moment they first perceived pain, at which point the pain threshold was recorded. **Blood Lactate Concentration**: The measurement of blood lactate concentration post-exercise provides critical insights into the metabolic impact of the HIIT protocol on participants.