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Sprint mechanics
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SPRINT ACCELERATION MECHANICS AND TRAINING
New technology, New concepts, New perspectives…
J-B Morin, PhD Laboratory of Exercise Physiology University of Saint-Etienne, France
Running&speed&and&acceleration&is&NOT&in&our&nature…&
Laboratoire de physiologie de l’exercice �
Studying sprint speed….why?
Lieberman et al. Nature, 2004�
Laboratoire de physiologie de l’exercice �
Life Magazine, 1955�
45 km/h
Studying sprint speed….why?
Survival of the fastest…
Acceleration is the key…
Studying sprint speed….why?
PRODUCE FORCE
« TRANSMIT IT » TO THE GROUND
REPEAT WITH HIGH RATE of MOVEMENT
VARIABLE POSITIONS and DIRECTIONS
Sprint Acceleration Mechanics – Nov. 2013
Understand - Evaluate - Improve OVERVIEW
! MEASURING*FORCE*OUTPUT*DURING*SPRINT*RUNNING*
! PRODUCE*FORCE…AND*TRANSMIT*IT*WITH*EFFECTIVENESS*
! ROLE*OF*HIP*EXTENSORS?*
! WORKSHOP:*F:V*PROFILING,*SIMPLE*FIELD*METHODS*
Sprint Acceleration Mechanics – Nov. 2013
2010,%new%technology…%
Sprint Acceleration Mechanics – Nov. 2013
INSTRUMENTED TREADMILLS (FORCES 3D= YES; SPRINT = NO)
CYCLE-ERGOMETERS Velocity - Force - Power
SPRINT TREADMILLS (SPRINT = YES; FORCES 3D= NO)
Validate a device that cumulates these features
-1
0
1
2
3
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Temps (s)
For
ce (B
W) Verticale
Horizontale
Existing methods…
Sprint Acceleration Mechanics – Nov. 2013
Instrumented&treadmill&
Weyand et al., 2000 - ��
11,7 m/s !!
Realistic&Top&speed&values&Ground&reaction&force&(VTC)!&NO&Acceleration&phase&ONLY&top&speed&is&studied&NO&Horizontal&force&measurement&
Sprint Acceleration Mechanics – Nov. 2013
• « Push vertical to run fast »
« We conclude that human runners reach faster top speeds not by repositioning their limbs more rapidly in the air, but by applying greater support forces to the ground. » 2000
Influential sprint and top speed researches
(Peter Weyand)
Sprint Acceleration Mechanics – Nov. 2013
Mea
n ve
rtic
al G
RF
(BW
)
6 to 12 m/s !
24 Men
9 Women Olympians
Only Vertical GRF is measured….and…
Sprint Acceleration Mechanics – Nov. 2013
3D Ground Reaction Forces, Speed, Power, 1000 Hz, step-averaged values…
Sprint Acceleration Mechanics – Nov. 2013
Sprint Acceleration Mechanics – Nov. 2013
Instantaneous
Average per step
2012
New&perspectives&!&
Sprint Acceleration Mechanics – Nov. 2013
Category: Coaching
2011,%new%concept…%
Sprint Acceleration Mechanics – Nov. 2013
Sprint instrumented treadmill: for each step, averaged values of Horizontal, Vertical and Total Force
Pedaling mechanics, Effectiveness = Ftan / FTot = cos β
FR
FTan FTot
β Davis & Hull 1981 Lafortune & Cavanagh, 1983
1. Concept of « Ratio of Force » RF
HZT
VTC TOT
Maximise RF in sprint running does not make sense (in cycling it does) Maintain a high RF during the acceleration makes sense…
Sprint Acceleration Mechanics – Nov. 2013
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
Sprint Acceleration Mechanics – Nov. 2013
Publication in process
Similar values of GRF, linear RF-speed relationships, similar Drf values
INSEP
PB = 9.95 s
Similar to
Start
Limit: Treadmill study = Treadmill results ?
Sprint Acceleration Mechanics – Nov. 2013
• INSEP-Paris: 3D Force Measurements for 18 steps over 40-m accelerations • 9 elite and high-level sprinters (9.95 – 10.5 s)
What&relationship&with&sprint&performance?&
HZT
• 12 subjects (2 sprinters) • Treadmill sprint • Just before or after : track 100-m
S100 D4s (Team sports) vs.
« Physical » capability Force Production (Hzt, Vtc, Tot)
« Technical » ability To apply this force with effectiveness (DRF)
Sprint Acceleration Mechanics – Nov. 2013
HZT
• Main results…
And: FTot (BW) was not correlated to DRF
« Physical Capability » of Force Production
« Technical Ability » of Force Transmission
Significant correlations in bold
Mean Speed 100 m
4 s Distance
Sprint Acceleration Mechanics – Nov. 2013
HZT
Subject ": Long jumper (15 yrs of practice, 100-m best time : 10.90s) Subject #: non-specialist (cyclist)
Typical example
1er pas • Subjects 2 and 11
Sujet 11 Sujet 2
Mass (kg) 68.1 69.9
Tot Force (BW) 1.87 1.89
RF max (%) 37.1 41.3
Drf -0.051 -0.083
100 m (s) 11.9 13.66 Smax (m/s) 9.96 8.80 D-4s (m) 26.3 23.3
CONCLUSIONS: The effectiveness of force
application is more important than the total amount of force
produced
(Limited to this population…)
Sprint Acceleration Mechanics – Nov. 2013
When sport meets science, a case study
Morin et al. 2012
200m Junior World Champ. 2008
100m: 10.28 s 2010: 9.98 s 2011: 9.92 s
9.92 s: No systematic / heavy strength training Not a « muscular » guy (best 1/2 squat ≈120 kg) At 21, only 5 yrs after his T&F debut
Sprint Acceleration Mechanics – Nov. 2013
• 6-s sprint on the treadmill • 100-m field sprint
Ground reaction forces • Fv • Fh • FTot
RF – speed Drf
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)
Ra
tio
de
fo
rce
s
Speed (m/s)
Sprint Acceleration Mechanics – Nov. 2013
Main results…
Confirms our previous results ! How the resultant force is applied is more important than its magnitude
2011
Sprint Acceleration Mechanics – Nov. 2013
Remember the typical subjects…
HZT
": Long jumper #: Non-specialist (cyclist)
Sujet " Sujet #
Mass (kg) 68.1 69.9
FTot (BW) 1.87 1.89
RF max (%) 37.1 41.3
Drf -0.051 -0.083
100-m (s) 11.9 13.66
Smax (m/s) 9.96 8.80
D4s (m) 26.3 23.3
CL
80.5
11.2
31.0
10.35
1.90
44
-0.042
« Take-Gym Message »
For a very similar FTot, He is able to produce 25% more HZT force…
Sprint Acceleration Mechanics – Nov. 2013
WCS
The higher the speed, the larger the difference in RF….
Question: How can we produce high HZT force AT HIGH SPEED ???
Sprint Acceleration Mechanics – Nov. 2013
Synchronized EMG and 3D Forces Sprint and repeated sprint (fatigue)
Foot and knee 2D motion
PRE-POST Isokinetic testing (H/Q)
2013%«%The%hip%extensors%study%»….St#Etienne,)Auckland,)Murcia)
Sprint Acceleration Mechanics – Nov. 2013
First Results….
Isokinetic Force alone NOT correlated to ground reaction forces
EMG alone: NOT correlated to ground reaction forces
Multiple regressions: FHZT explained by: Hamstring Eccentric Force “+” EMG end of swing
Quadriceps….Gluteus….Contact Phase: Nothing
FVTC explained by: NOTHING we measured…
2013%«%The%hip%extensors%study%»….St#Etienne,)Auckland,)Murcia)
Sprint Acceleration Mechanics – Nov. 2013
«)Prepare)and)Repair…..)»)
Importance of horizontal force production (especially at high speed)
Total force production capability: is it that important ?!
What balance between hip extensor and flexor muscle groups?
Hamstring eccentric force and activation: Performance AND Injury prevention !
Sprint Acceleration Mechanics – Nov. 2013
TRANSMISSION
Sprint Acceleration Mechanics – Nov. 2013
«)A)chain)is)only)as)strong)as)its)weakest)link)»)…..whatever the force of the strongest link….
WORKSHOP: F-V PROFILING IN SPRINT & JUMP
J-B Morin, PhD Laboratory of Exercise Physiology University of Saint-Etienne, France
EVALUATE « ABSOLUTE » MAXIMAL VELOCITY
Force as a « distorting » factor
In!ALL!these!situations,!a!certain!amount!of!force!is!produced……..!!
In!these!cases,!velocity!is!NOT!MAXIMAL!POWER!is!tested,!rather!than!«!Velocity!»!
Sprint Acceleration Mechanics – Nov. 2013
FORCE – VELOCITY – POWER
Actual!«!maximal!»!velocity!can!be!studied!through!FJV!relationship…!
Forc
e (N
.kg-
1 )
Vitesse (m.s-1)
« V0 »
« F0 » Maximal theoretical Force and Velocity Even with no additional load (SJ), the level of force output is not negligible
Sprint Acceleration Mechanics – Nov. 2013
OK,!how!is!it!possible!out!of!the!lab!??!
Sprint Acceleration Mechanics – Nov. 2013
Mechanical work during the “Squat Jump” push-off
g( po )W m h h= +
p1
og
hmh
F ! "= +# $
% &
g2
V h=
g1
p 2og h hh
P m ! "= +# $
% & 2
vol
8gth =
Knees ≈90°
Start position take-off Max height
Validated against force plate 2000 Hz
High agreement, Mean absolute bias < 3%
OK WITH DIFFERENT LOADS…
Sprint Acceleration Mechanics – Nov. 2013
Sprint Acceleration Mechanics – Nov. 2013
Forc
e (N
.kg
-1)
Velocity (m.s-1) v0
F0
Po
wer
(W
.kg
-1) Pmax
Forc
e (N
.kg
-1)
Velocity (m.s-1)
v0
F0
Po
wer
(W
.kg
-1) Pmax
For a same given Pmax ,
Many possible profiles….
Which one maximizes performance ??
« Velocity » Profile « Force » Profile
Athlete 1 Athlete 2
Sprint Acceleration Mechanics – Nov. 2013
2012
Concept%of%«%Optimal%FCV%ProFile%»….)
Sprint Acceleration Mechanics – Nov. 2013
“…experimentally.supports.the.actual.existence.of.an.optimal.F6v.profile,.specific.to.each.individual,.that.maximizes.jumping.performance.for.a.same.given.!!"#...
CONCLUSION
In press
Sprint Acceleration Mechanics – Nov. 2013
Concept%of%«%Optimal%FCV%ProFile%»….)
In progress…
! Partnerships (football, basketball, rugby, tennis, athletics) ! First long-term follow-ups initiated all over the world ! Experiments: Training vs. Control Groups…
Sprint Acceleration Mechanics – Nov. 2013
FORCE – VELOCITY - POWER
What!about!SPRINT!RUNNING!???!
Sprint Acceleration Mechanics – Nov. 2013
Sprint performance analysis…
« Speed-time curves » ! 1927, Archibald HILL, pioneer
What could be possible with field devices?
RADAR, GPS, Photocells, iPhone ??
Sprint Acceleration Mechanics – Nov. 2013
v(t) = vmax.(1-e(-t/τ))
di Prampero et al., J Exp biol, 2005
a(t) = (vmax/τ).e(-t/τ))
x(t) = vmax.(t + τ.e(-t/τ))- vmax.τ
vmax
τ
A New Simple Method
Furusawa et al., 1927 Henry, 1954 Volkov & Lapin, 1979
OR
"!#(%)/"%(
∫↑▒#(%)!"%
Fundamental law of dynamics….
Sprint Acceleration Mechanics – Nov. 2013
P-F-V profiling in sprinting
a(t) = (vmax/τ).e(-t/τ))
A New Simple Method
Fh(t) = m.a(t) + Fair
Samozino et al., ISB 2013, Natal
Estimated from stature and body mass (and wind if measured) Arsac & Locatelli, JAP, 2002
Ph(t) = Fh (t) . v(t)
v(t)
Ph(t) Fh(t)
F0
V0
Pmax
Samozino et al., in preparation
Inverse quasi-linear F-v relationship Parabolic P-v relationship Validity ??
Sprint Acceleration Mechanics – Nov. 2013
! Comparison to track force plate data (F-V, Pmax) ! Validation from radar or photocells data
Paper in preparation…
Ex. Usain Bolt’s World Record
INSEP Paris
Sprint Acceleration Mechanics – Nov. 2013
Example: 2011-2012 Season Follow-up of Lemaitre
First meeting…
Winter…
One week before London…
Sprint Acceleration Mechanics – Nov. 2013
TYPICAL&EXAMPLE:&The&guy&is&slow……but&has&high&velocity&capabilities&!&
& && He&does¬&seem&to&need&velocity&workout&
Sprint Acceleration Mechanics – Nov. 2013
JUMP
Innovation: all that with an iPhone / iPad ?! « FitTests » app
SPRINT www.fit-tests.com
Sprint Acceleration Mechanics – Nov. 2013
CONCLUSIONS…Potential applications… STUDIES IN PROGRESS
M. Buchheit
J. Mendigutchia
P. Edouard
Sprint Acceleration Mechanics – Nov. 2013
M. Brughelli