## 4 Discussion  
We assessed the biomechanics characteristics of the Isabel CrossFit(r) workout, which is typically performed in ~120 s and elicits very significant energy demands [4]. Our mains findings were that: (i) an increase in total lift time, and decrease maximal lift velocity and maximal lift power occurred in the middle phase and continued to decrease throughout the elevation; (ii) average lift power decreased until the workout final phase, remaining constant in the last two phases; (iii) there was a gradual decrease in the time from lift until the bar crossed the hip and shoulder throughout the routine, with the lowest values being observed in the final phase; and (iv) as the number of repetitions succeed, a trend toward a decreased hip flexion was observed during the last two phases when the bar crossed the knee, while an increase in knee extension was noted when the bar cross the shoulder. Collectively, these outcomes indicate that the high demands of Isabel workout impact the power profile of crossfitters, while also affecting changes in hip flexion throughout the specific workout without compromising the other joints. While the biomechanics of the snatch during single repetition efforts are well documented in the literature, particularly in weightlifting and powerlifting [16; 19], research in the context of CrossFit(r) is scarce, especially using benchmark workouts under real exercise conditions. In the current study, the substantial volume of repetitions with a constant load impacted the total lift time, velocity and maximal power production throughout the workout. This decline was expected and aligns with the increased metabolic demands and muscle fatigue associated with extreme-intensity exercise over time [4; 10]. Moreover, the decrease in the average lift power until the workout final phase, while remaining constant in the last two phases, suggests a potential adaptation of performance despite the continued effort. This adjustment in pacing likely reflects an attempt to maintain consistent performance levels despite increasing fatigue, slowing the velocity of muscle contraction [24; 25]. The time from lift until the bar crosses over the knee, hip and shoulder progressively increased throughout the Isabel routine, correlating with the increase in time to reach maximal lift velocity. These results are supported by findings that elite weightlifters experience a decline in barbell velocity, potentially due to excessively rapid initial movement or fatigue [19; 26]. Previous research has demonstrated that the Isabel workout performed in ~2 min exhibits a greater anaerobic predominance, reflecting the increased recruitment of type II muscle fibers, which are more susceptible to fatigue [4]. Furthermore, increases in external load during multi-joint exercises can result in greater task demands on skeletal muscle function [25; 27]. Even if we did not observed a rise in external load (e.g., 70-90% of one repetition maximum), there was an increase in the total volume of repetitions, influencing the time instant the bar crosses the joints [28]. The observed decrease in hip flexion during the last two phases of the Isabel workout, as the bar crosses the knee, aligns with studies on biomechanics of weightlifting [19]. When the crossfitter takes the bar off the floor, the knee angle tends to increase towards maximum extension [16; 26] and the lifter actively pushes the knees towards the bar, facilitating the transition into the pull point [19; 21]. This pattern often relates with a decrease in hip flexion as the numbers of repetitions increase, reflecting the dynamic adjustments in movement mechanics throughout the workout [29]. This suggests that during the period between lifting and crossing the bar at the hip, the lower limbs may be participating less in generating force, increasing the demand on the trunk extensor muscles to complete the required numbers of repetitions [29].