Oral presentation at ISB Glasgow 2015: Sprint acceleration mechanics and the role of hip extensors

1. SPRINT
ACCELERATION
MECHANICS
THE
ROLE
OF
HAMSTRING
MUSCLES
IN
HORIZONTAL
GROUND
REACTION
FORCE
PRODUCTION
@jb_morin
Morin JB University of Nice, France
Edouard P University of Saint-Etienne, France
Gimenez P University of Franche-Comté, France
Arnal P University of Saint-Etienne, France
Jimenez-Reyes P Catholic University of San Antonio, Murcia, Spain
Samozino P University of Savoy, France
Mendiguchia J Zentrum Rehab Center, Baranian, Spain
Brughelli M Auckland University of Technology, New-Zealand
jean-benoit.morin@unice.fr

2. Survival of the fastest?
Acceleration is the key…

3. 2011
-­‐
2015
Sprint
acceleration:
importance
of
Horizontal
Force
Production
Sprint
Instrumented
treadmill
Track-­‐Embedded
Force
Plates
Elite
Athletes
Med
Sci
Sport
Exerc
2011
Eur
J
Appl
Physiol
2012
Scand
J
Med
Sci
Sport
2015
J
Biomech
In
Press
Horizontal
GRF
/
impulse
is
paramount
Vertical
/
resultant
GRF
is
not
«
Ratio
of
Forces
»
and
Hzt
Force
at
high
speed
higher
in
top
athletes

4. Higher RF at high, not low speeds…
How to produce High net HZT Force
At High running speed??
The
«
Hip
Extensors
»
hypothesis

5. Synchronized EMG (2 kHz) and
3D GRF (1 kHz)
Treadmill
Sprint
Accelerations
2D Motion
Knee and
Foot
Knee Extensor
Hip Extensor
Isokinetic Torque
The
«
Hip
Extensors
»
hypothesis

6. The
«
Hip
Extensors
»
hypothesis

8. Preliminary results….
Paper
in
preparation
Isokinetic Torque alone NOT correlated to GRF
Muscle activity (EMG) alone: NOT correlated to GRF
Multiple Regressions:
FHZT entire acceleration correlated to : Eccentric Hamstring torque
EMG BF during end-of-swing phase
FHZT initial acceleration correlated to : Eccentric Hamstring torque
EMG BF during end-of-swing phase
Concentric Glutei torque
EMG Glut during end-of-swing phase
Quadriceps…. Contact phase: NS
2D Motion (speed, range of motion) of Knee and Foot: NS

9. «
Prepare
and
Repair
»
Importance of Horizontal GRF (especially at high speed)
What balance between hip extensors and other groups in training?
Hamstring Eccentric Force and Activation:
Performance AND Injury Prevention
Associated with: high hip extensors force (Glut in CONC and Ham in ECC)
high end-of-swing EMG activity

10. MERCI !!