ISBS 2015 Sprint Applied Session, Theoretical Part
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This document proposes a simple field method to measure external force, power output, and effectiveness of force application during sprint acceleration. It involves modeling sprint speed using a curve and computing net horizontal force and power output over time. The method has been validated against force plates and applied to analyze elite sprinters including Usain Bolt. The data collected can be used for applications in coaching, training, and injury management and prevention by providing a force-velocity-power profile of individual athletes.
ISBS 2015 Sprint Applied Session, Theoretical Part
- 1. A SIMPLE METHOD TO MEASURE EXTERNAL FORCE, POWER OUTPUT AND EFFECTIVENESS OF FORCE APPLICATION DURING SPRINT ACCELERATION @jb_morin J-B Morin Professor University of Nice, France jean-benoit.morin@unice.fr
- 2. Things as they are…. Work in progress… 2010 Field Field
- 3. Only 2 (im)possibilities L SPRINT INSTRUMENTED TREADMILL St-Etienne, France Doha, Qatar FORCE PLATES INSEP, Paris, France 2015, a simple .ield method
- 4. 1927 Archibald V. HILL 1950’s Franklin Henry Modern Devices v(t) = vmax.(1-e(-t/τ)) vmax di Prampero et al., J Exp biol, 2005 Furusawa et al., 1927 Henry, 1954 Volkov & Lapin, 1979 2015, a simple .ield method
- 5. a(t) = (vmax/τ).e(-t/τ)) Fh(t) = m.a(t) + Fair Estimated from speed, mass and height Ph(t) = Fh (t) . v(t) v(t) Ph(t) Fh(t) Linear F-V relationship Polynomial 2 P-V relationship Validity ?? F0 V0 Pmax 2015, a simple .ield method
- 6. 2015, a simple .ield method • INSEP-Paris: 3D GRF for 18 steps over 40-m sprints • 9 Elite and sub-elite sprinters (2 sub-10 s) 6.60m force plates 0 - 6.60 m 6.60m - 13.2 m 14m - 20.6 m 2 sprints 23.4m - 30 m 33.4m - 40 m 2 sprints 1 sprint 1 sprint 1 sprint Very high reproducibility… !
- 7. Comparison with force plates: Validity, Reproductibility J 2015, a simple .ield method
- 8. Pierre Samozino, PhD University of Savoy FORCE-‐VELOCITY-‐POWER Pro1ile of Usain Bolt’s World Record Running Speed (m/s) Distance (m) S(t) = Smax 1−e−t/τ ( ) Field Measurements In competition conditions Computing Modeled Speed-‐time curve Computed Net Horizontal Force output Max Power Output of 30 W/kg reached after about 1 s… Power = Force x Speed… SpeciJic, Field Sprint Force-‐Velocity-‐Power proJile Jean-‐Benoit Morin, PhD University of Nice “F0” “V0” Pmax Vopt F0 and V0 are the theoretical maximal outputs of the system Vopt is the speed at which Pmax is produced The magnitude of the slope (F0/V0) describes the Force-‐Velocity proJile of the athlete
- 9. DEVICES… Stalker ATS Pro II Speed-time curves Timing Gates 5 split times Appropriate trigger… GPS Units ?? Speed-time curves R. Nagahara 21 subjects, 5Hz GPS vs 100 Hz Laser Average data…
- 10. Category: Coaching 2011, Concept of Effectiveness…
- 11. For each step, averaged values of Horizontal, Vertical and Total Force 1. Concept of « Ratio of Force » RF HZT VTC TOT 2011, Concept of Effectiveness…
- 12. y = -0.0805x + 0.6584 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 2.0 3.0 4.0 5.0 6.0 7.0 Vitesse (m/s) Ratiodeforces Velocity of Step after step, the RF decreases…. for all athletes…. 2. Decrease in the RF: Drf Slope = index of the effectiveness of force application onto the ground (Drf) Step 1 Step 6 Very efficient Not efficient 2011, Concept of Effectiveness…
- 13. We also compute the Ratio of Force ! After 50% of Vmax, Fv = m.g 2015, a simple .ield method
- 15. Example: Season follow-up of C. Lemaitre 1st meeting… Winter… 3 days before London… Applications: training
- 16. Individual comparisons + Team Season Follow-up… Applications: training
- 17. TYPICAL EXAMPLE: The player is « low » on 40m……But has high velocity skills! Applications: training
- 18. TYPICAL EXAMPLE: Same 30m time, but different capabilities…. DIFFERENT TRAINING PROGRAMS ?! PLAYER 1 T30: 4.9 sec 4.8 sec V0: 11.2 m/s 9.5 m/s F0: 5.15 N/kg 7.5 N/kg PLAYER 2 Applications: training
- 20. Applications: Injury Management (prevention / rehab)
- 21. BETTER TRAINING PROGRAM = PREVENTION ! PLAYER 1 T30: 4.9 sec 4.8 sec V0: 11.2 m/s 9.5 m/s F0: 5.15 N/kg 7.5 N/kg PLAYER 2 Applications: injury management
- 22. Mendiguchia et al. Int J Sports Med, 2014 Jurdan Mendiguchia Zentrum Center, Baranain Applications: injury management
- 23. Mendiguchia et al. Int J Sports Med, 2014 At « Return to Sport » (post hamstring injury): Ø Pmax and F0 (not V0) lower in injured group Ø 2 months later, values back to « normal » (non-injured)… 1/ what objectvie/functional tests were used to give « RTS » ? 2/ what risks during this 2-‐month (or less) period!? Applications: injury management
- 24. « Case study » Elite Soccer player Applications: injury management
- 25. 2-‐season cohort follow-‐up study (soccer, rugby, sprint…) 1/ Is F-‐V-‐P pro.ile related to a higher risk of injury? 2/ Is it an interesting functional variable in injury management? 3/ Does it have a predictive feature? Applications: injury management Collaborators: R. Nagahara, Japan - J. Mendiguchia, Spain - P. Samozino, France