Technical Ability of Force Application as a Determinant Factor of Sprint Performance

MORIN, J-B., P. EDOUARD, and P. SAMOZINO. Technical Ability of Force Application as a Determinant Factor of Sprint Performance. Med. Sci. Sports Exerc., Vol. 43, No. 9, pp. 1680-1688, 2011. Purpose: We transposed the concept of effectiveness of force application used in pedaling mechanics to calculate the ratio of forces (RF) during sprint running and tested the hypothesis that field sprint performance was related to the technical ability to produce high amounts of net positive horizontal force. This ability represents how effectively the total force developed by the lower limbs is applied onto the ground, despite increasing speed during the acceleration phase. Methods: Twelve physically active male subjects (including two sprinters) performed 8-s sprints on a recently validated instrumented treadmill, and a 100-m sprint on an athletics track. Mean vertical (F-V), net horizontal (F-H), and total (F-Tot) ground reaction forces measured at each step during the acceleration allowed computation of the RF as F-H/F-Tot and an index of force application technique (D-RF) as the slope of the RF-speed linear relationship from the start until top speed. Correlations were tested between these mechanical variables and field sprint performance variables measured by radar: mean and top 100-m speeds and 4-s distance. Results: Significant (r > 0.731; P < 0.01) correlations were obtained between D-RF and 100-m performance (mean and top speeds; 4-s distance). Further, F-H was significantly correlated (P < 0.05) to field sprint performance, but F-Tot and F-V were not. Conclusions: Force application technique is a determinant factor of field 100-m sprint performance, which is not the case for the amount of total force subjects are able to apply onto the ground. It seems that the orientation of the total force applied onto the supporting ground during sprint acceleration is more important to performance than its amount.