{'fraction_non_alphanumeric': 0.05055849500293945, 'fraction_numerical': 0.03350970017636684, 'mean_word_length': 4.455128205128205, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Influence of ethnic origin on predictive parameters of performance in sprint running in prepubertal boys.

Afro-American and Caribbean athletes have long dominated sprint running, although the reasons for their disproportionate success remain unclear. The studies of sprinting ability in blacks versus whites have shown contradictory results. This study compared the anthropometric measurements and the physical test results (vertical jump and sprint) of Caucasian and Afro-Caribbean prepubertal boys. Seventeen healthy untrained prepubertal boys, 8 Caucasians and 9 Afro-Caribbeans (11.49 +/- 0.74 years) performed vertical jump tests (a countermovement jump according to the Sargent method, using Abalakov material) and short sprints (30 m). Age, height, weight, and fat mass percentage were also recorded. The sprints were filmed to determine the number of strides over the 30 m. No significant difference was noted for sprint performance between the Caucasians and Afro-Caribbeans (respectively, 5.59 seconds +/- 0.44 vs. 5.51 s +/- 0.50). The predictors of sprint performance differed between the two groups: the vertical jump test was the main predictor for the Caucasian group, whereas the stride number/height ratio was the main predictor for the Afro-Caribbean group. This last group had better ratio (0.14 +/- 0.15 vs. 0.16 +/- 0.02, p < 0.05) and better jump test results (36.77 cm +/- 2.90 vs. 31.12 cm +/- 4.76, p < 005). The prepubertal Afro-Caribbeans seemed to be endowed to run faster but they did not. We hypothesize that they were unable to use their greater leg strength to develop an optimal stride. Further study is needed to investigate what occurs at other maturational stages.