1. A new method to evaluate hamstring injuries in soccer
Authors:
Archit Navandar
Raquel Antonio
Enrique Navarro
Marco Gulino

2. Index
Introduction
Methodology
Results & Discussion
Conclusion

3. Introduction

4. Introduction
Injuries in Soccer
Injury rate: 3.7 to 29.1 injuries per 1000h (practice and games). [Kellis, Katis & Gissis, 2004]
Majority in lower extremeties: most common -- the hamstring strain.
Economic Loss (injuries ~ £74.7 million, Premier league, 1999–2000). [Foreman et al., 2006]
references 4

5. Hamstring Injuries Frustrating: 1.Symptoms are persistent.
Introduction
Hamstring Injuries
European soccer (10 y):
Muscle injuries: nearly 1/3 of all injuries, 37 % = hamstrings
[Erkstrand et al., 2011]
English soccer: 81% of thigh injuries affect hamstrings.
[Greig & Seigler, 2009]
English and Australian professional soccer: Hamstring strains: 12–16%
[Petersen & Holmich, 2005]
Frustrating:
1.Symptoms are persistent.
2. Healing is slow.
3. Rate of re-injury is high. 5

6. Hamstring strain: What exactly happens
Introduction
Hamstring strain: What exactly happens
Latter part of the swing phase: hamstring fibres rapidly lengthened
Hip Flexion
Knee Extension
Hamstrings change: eccentric to concentric
Decelerate knee extension 
Active extensor of the hip joint
Rapid change from eccentric to concentric
Greater biomechanical loads 
Susceptibility to injury 6

7. Evaluation of Hamstring Injuries
Introduction
Evaluation of Hamstring Injuries
Traditional Methods
EMG
Muscle Activation
No Quantification
Isokinetic
Far from Reality 7

8. Introduction
Need of the Hour
Test that mimics the movements that professional soccer players undergo on a regular basis. 8

10. Objectives Introduction 1
Develop a new procedure to evaluate the effect of hamstring injuries. 2
Investigate the difference between the biomechanical kicking pattern between athletes with a previous history of hamstring injuries and those without one. 3
Compare the results with tests on hamstring strength using isokinetic testing methods.

11. Methodology

12. Data Capture 6 camera VICON motion capture system at 500 Hz.
Methodology
Data Capture
6 camera VICON motion capture system at 500 Hz.
IBV Force Platform at 500 Hz.
Both synchronized.
17 professionals.

13. Methodology
Placement of Markers 13

14. Procedure 20 minute warm-up
Methodology
Procedure
20 minute warm-up
sprinting,
aerobic and stretching exercises
soccer-specific strength exercises
Kicks with their dominant foot, with a 2 step run up, as hard as possible.
5 instep kicks.
5 side-foot kicks.
Support leg on the platform. 14

15. Definition of Local Reference Systems
Methodology
Definition of Local Reference Systems Z Y X
Marker trajectories filtered using Woltring’s quintic smoothing spline (MSE = 5 mm).
Ground Reaction Forces: Low pass (50 Hz).
Joint centres determined at hip, knee and ankle.
Inter-segmental angles calculated using Euler system.
Standard inverse dynamics procedure to calculate joint reaction forces and moments. 15

16. Phases of Kicking Backswing Leg Acceleration Follow Through
Methodology
Max Hip Extension
Ball Impact
Max Hip Flexion
Backswing
Leg Acceleration
Follow Through 16

17. Highest position of Knee
Methodology
Time Instances
Time Instances T1
Toe Off T2
Maximum Hip Extension T3
Ball Impact T4
Maximum Hip Flexion T5
Highest position of Knee 0%
100% 17

18. Isokinetic Torque Measurement
Methodology
Isokinetic Torque Measurement
Isokinetic dynamometer (PRIMUSRS).
10 minute warm-up prior to the testing.
Maximum voluntary concentric torque for the quadriceps and hamstrings.
10 warm-up trials at 180°/s.
3 at 60° /s.
5 at 120°/s. 18

19. Statistics Kicking Leg Support Leg Injured Un-injured
Methodology
Statistics
Kicking Leg
Support Leg
Injured
Un-injured
Non-parametric: Mann-Whitney U tests.
[α = 0.05, confidence interval = 95%] 19

20. Results & Discussion

21. Normalized Temporal Variables
Results & Discussion
Normalized Temporal Variables
Backswing %
Leg Acceleration %
Follow Through %
Injured
22.62 ± 4.36
31.05 ± 4.03
39.41 ± 3.57*
Not-injured
24.40 ± 6.73
33.07 ± 5.12
35.85 ± 5.91*
Total
23.98 ± 6.17
32.59 ± 4.85
36.69 ± 5.57
* Significance : p < 0.05 21

22. Normalized Temporal Variables
Results & Discussion
Normalized Temporal Variables
Difference in follow through?
Decrease the angular velocity of the thigh;
Poor activation of the hamstrings in previously injured limbs (hamstring activation is believed to play an important role in the deceleration of the knee).

23. Hip Flexion/Extension Moment
Results & Discussion
Hip Flexion/Extension Moment
Extension
Flexion 23

24. Hip Flexion/Extension Moment
Results & Discussion
Hip Flexion/Extension Moment BS
Initial flexion moment peaking at T2. LA
Flexion moment decreased, turning to an extension moment.
Small backward moment at ball impact. FT
Further increase in extension moment.
Hamstring activation. 24

25. Hip Flexion/Extension Moment at Various Instances
Results & Discussion
Hip Flexion/Extension Moment at Various Instances
Side-foot Hip
(Nm/kg)
Instep
Max. Hip Flexion Moment
Ball Impact
Peak Extension Moment
Injured
-2.84 ± 0.23**
1.15 ± 0.16
1.48 ± 0.24
-3.03 ± 0.13*
0.70 ± 0.49
2.28 ± 0.66
Not-injured
-2.48 ± 0.32**
1.15 ± 0.43
1.42 ± 0.46
-2.51 ± 0.36*
0.87 ± 0.37
2.09 ± 0.6
Total
-2.57 ± 0.33
1.15 ± 0.38
1.44 ± 0.41
-2.63 ± 0.39
0.83± 0.39
2.13 ± 0.59 25
* Significance : p < 0.05, ** Significance: p < 0.01

26. Why is there a difference in Max. Hip Flexion Moment?
Results & Discussion
Why is there a difference in Max. Hip Flexion Moment?
Prevention mechanism to reduce the angle of hip extension and knee flexion at the end of the back-swing phase.
Shorter backswing phase. 26

27. Knee Flexion/Extension Moment
Results & Discussion
Knee Flexion/Extension Moment
Flexion
Extension 27

28. Knee Flexion/Extension Moment
Results & Discussion
Knee Flexion/Extension Moment BS
Initial extension moment peaking after T2. LA
Pre-stretching moment of the quadriceps: Extension moment  flexion moment, peaking before ball impact.
Activation of the hamstring biarticular muscle affecting the hip & knee. FT
This flexion moment rapidly increases, peaking before T4.
Related to the eccentric activation produced by the hamstring to decelerate the extension of the knee.

29. Knee Flexion/Extension Moment at Various Instances
Results & Discussion
Knee Flexion/Extension Moment at Various Instances
Side-foot
(Nm/kg)
Instep
Peak Extension Moment
Ball Impact
Peak Extension Moment of Hip
Injured
-0.80 ± 0.03
0.61 ± 0.12
0.57 ± 0.02
-0.82 ± 0.14
0.68 ± 0.10
0.83 ± 0.31
Not-injured
-0.79 ± 0.17
0.64 ± 0.17
0.41 ± 0.39
-0.84 ± 0.14
0.73 ± 0.19
0.67 ± 0.21
Total
-0.79 ± 0.14
0.63 ± 0.16
0.45 ± 0.34
0.72 ± 0.17
0.71± 0.23

30. Isokinetics Greater in the dominant leg  Ratio < 1
Results & Discussion
Isokinetics
Non-Dominant Hamstring Strength
Dominant Hamstring Strength
Greater in the dominant leg
 Ratio < 1
Ratioinjured > Ratioun-injured
at 60°/s and 120°/s
(not significant). 30

31. Conclusions

32. Conclusions
Conclusions
To our knowledge, first biomechanical study to record and the entire kicking motion at 500 Hz.
Professionals kicking the ball, rather than seated in their position  closer to reality.
Quantification of biomechanical loads acting on muscles and joints.

33. Injured v/s Un-injured
Conclusions
Injured v/s Un-injured
Significant difference:
Time for follow through.
Max. hip flexion moment.

34. Motion Capture v/s Isokinetics
Conclusions
Motion Capture v/s Isokinetics
No significant differences observed in isokinetics.
Could indicate: certain differences come out when players are performing their “natural” movement (kicking) rather than in a seated position.

35. Muchas gracias por su atención
Thank you
Muchas gracias por su atención

36. A new method to evaluate hamstring injuries in soccer
Authors:
Archit Navandar
Raquel Antonio
Enrique Navarro
Marco Gulino