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

Index Introduction Methodology Results & Discussion Conclusion

Introduction

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

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

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

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

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

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.

Methodology

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.

Methodology Placement of Markers 13

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

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

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

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

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

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

Results & Discussion

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

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).

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

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

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

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

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

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.

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

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

Conclusions

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.

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

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.

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