ISBS 2015 Sprint Applied Session, Theoretical Part
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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 [email protected]
Transcript of ISBS 2015 Sprint Applied Session, Theoretical Part
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
Things as they are….
Work in progress…
2010
Field Field
Only 2 (im)possibilities L
SPRINT INSTRUMENTED TREADMILL St-Etienne, France Doha, Qatar
FORCE PLATES INSEP, Paris, France
2015, a simple .ield method
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
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
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…
!
Comparison with force plates: Validity, Reproductibility J
2015, a simple .ield method
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
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…
Category: Coaching
2011, Concept of Effectiveness…
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…
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 7.0Vitesse (m/s)
Rat
io d
e fo
rces
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…
We also compute the Ratio of Force !
After 50% of Vmax, Fv = m.g
2015, a simple .ield method
Applications: optimized training
Example: Season follow-up of C. Lemaitre
1st meeting…
Winter…
3 days before London…
Applications: training
Individual comparisons + Team Season Follow-up…
Applications: training
TYPICAL EXAMPLE: The player is « low » on 40m……But has high velocity skills!
Applications: training
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
Martin Buchheit PSG
Applications: training
Applications: Injury Management (prevention / rehab)
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
Mendiguchia et al. Int J Sports Med, 2014
Jurdan Mendiguchia Zentrum Center, Baranain
Applications: injury management
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
« Case study »
Elite Soccer player
Applications: injury management
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
