**3. Results**

The di fference in body weight between competitors was only 4 kg. An even greater di fference was in body height and was 10 cm in favor of Robles. Both measurements significantly di fferentiated hurdlers in terms of a measure of body fat (the ratio of the weight of the body in kilograms to the square of its height in meters), which was 1.21 in favor of Robles (Table 1). The time di fference between those two world records is 0.04s. Jackson set his world record at the age of 26 and Robles at the age of 22. The age di fference between competitors on the day of the experiment was approximately 10 years in favor of Jackson, and Robles obtained a better result by 0.47s in the 110 m performance.

Based on biomechanical analyses (Table 2), the following results were obtained: Robles's total stride length was 3.66 m, and the stride was completed in 0.33 s, while Jackson's stride length was 3.67 m, and it was slightly slower, lasting 0.36 s. During hurdle clearance, Dayron Robles reached the highest COM point at 1.38 m (0.32 m above the height of the hurdle), which corresponded to 72.2% of his body height. Colin Jackson reached the COM trajectory point at 1.52 m (0.45 m above the hurdle height), which was 83.4% of his height. The di fference between the lowest COM point in the eccentric phase of the take-o ff was 1.11 m for Robles and 0.95 m for Jackson; and the highest COM point during the flight phase was 1.387 m for Robles and 1.517 m for Jackson. The height of the COM at the end of the concentric phase of take-o ff for Robles was 1.24 m and 1.08 m for Jackson.


**Table 2.** Biomechanical variables of the clearance of the fifth hurdle.
