Sprint applied session at the ISBS conference in Poitiers, France, 2015

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

14. Applications:
optimized
training

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

19. Martin Buchheit
PSG
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