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Comparing selected kinematic parameters of the late swing phase during a sprint, isokinetic strength, and flexibility in male soccer players with and without anterior pelvic tilt
Vergleich ausgewählter kinematischer Parameter der späten Schwungphase während eines Sprints, isokinetischer Stärke und Flexibilität bei männlichen Fußballspielern mit und ohne anteriore Schwenkbewegung
Dokument 1.pdf (3.038 KB)
Freie Schlagwörter (Englisch):
Kinematic , Anterior Pelvic Tilt , Strength , Flexibility , SPM
Mattes Klaus (Prof. Dr.)
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
Introduction and theoretical background
Soccer is a competitive sport in which the players suffer a high amount of injury specifically muscle strain i.e. hamstring strain. Hamstring strain can be a categorized into two forms: contact or non-contact. The non-contact has been studied and the late swing phase has been proposed as the time point where the muscle is likely to suffer from an injury due to the lengthening occurring with regards to is normal length when standing upright. The literature suggests that the anterior tilt of the pelvis increases the risk of sustaining a hamstring injury while performing a sprint at the late swing phase. It is justified that the increase of the pelvis angle would lead to an increase in the musculotendon tension, which can eventually predispose the hamstring to sustain an injury. However, the kinematics and muscular activity of the pelvis, hip and knee region while performing a sprint at the late swing phase in soccer players with and without anterior pelvic tilt has yet to be fully understood.
Furthermore, risk factors such as flexibility and strength has been extensively studied, but a controversy yet remains as to if a deficiency in these parameters could predict the outcome of an injury, specifically hamstring strain. The previous studies did not however, incorporated the amount of pelvic tilt into their measurements, in order to analyse its relationship with the outcome of flexibility and strength results. The aim of this study was to theoretically and empirically analyze the association of pelvic tilt with hip and hamstring muscle flexibility, the EMG and kinematics of late swing phase while sprinting, and maximum isokinetic eccentric and concentric strength of the knee and hip muscles as well as the conventional and functional ratios.
Hamstring flexibility differs between soccer players with and without anterior pelvic tilt.
Hip flexors’ flexibility differs between soccer players with and without anterior pelvic tilt.
Sagittal kinematic parameters i.e. knee, hip and pelvis angle differ at the late swing phase in a sprint between soccer players with and without anterior pelvic tilt.
Neuromuscular activities of the gluteus maximus, rectus femoris, vastus medialis, and hamstring biceps femoris at the late swing phase during a sprint differ between soccer players with and without anterior pelvic tilt.
Maximum concentric and eccentric isokinetic strength for knee flexors, knee extensors, hip flexors and hip extensors and their ratio differ between soccer players with and without anterior pelvic tilt
A cross sectional, single measurement under lab conditions was conducted for the purpose of this research. Initially a total number of 38 soccer players were recruited from the Hamburg league, but due to the drop out during the measurements the number of participants reduced to 34. After a general warmup the players had their measurements taken for the spinal alignment, and hamstring and hip flexors’ flexibility. Hamstring flexibility was assessed using the 90:90 active knee extension clinical test. For the hip flexor flexibility the modified Thomas test was used. The measurements were taken using a photographic camera with reflective markers attached on the great trochanter, knee, and lateral malleolus. The pictures were taken from the sagittal plane and latter analysed using the Kinovea software. Next they proceeded to a sprint test in which the neuromuscular activity and the kinematic angles were recorded. The players performed three sprints at the speed of 6.9 m/s on a motorized treadmill. Using the template for the lower extremity, 40 markers were applied to the athletes in addition to the electrodes to record the electrical activity of their muscles. The average of 5 late swing phases for each player was extracted for both kinematic and EMG values for statistical analysis. Finally maximum isokinetic strength test was measured for the knee and hip joint. Peak torque values were taken for knee flexion and extension, and hip flexion and extension at 120 °/s concentrically and eccentrically. Conventional and functional strength ratios were also calculated for statistical analysis. The players were grouped using the Diers Formetric device into players with and without anterior pelvic tilt.
All data were assessed for their normality using Shapiro-Wilk normality test. Independent t-test was used for flexibility, peak torque, and pelvic tilt angle for comparison. For EMG and kinematic analysis a time series analysis was conducted using the SPM package. Since the kinematic data were normally distributed the parametric t-test was used and for the EMG the non-parametric t-test equivalent was used. All alpha levels were set to 0.05 and adjusted for using the Bonferroni correction.
The results show that the amount of pelvic tilt between two groups of players was significantly different (p < 0.001). The amount of hamstring flexibility showed significant difference between players with and without anterior pelvic tilt (p = 0.05) with an effect size of 0.79 which is considered a large effect size. No significant difference was indicated for the hip flexors flexibility between the players with and without anterior pelvic tilt (p > 0.05). For kinematic only hip flexion depicted significant difference (p < 0.05) at the late swing phase (85.2% - 100%) while sprint; with the players without anterior pelvic tilt demonstrating a higher hip flexion in comparison to those with anterior pelvic tilt. The effect size was calculated for this range to be 0.90-0.98 which is considered to be a large effect size. No other significant difference was found for other kinematic and EMG parameters. No significant difference was determined for maximum isokinetic strength test for knee and hip joints (p > 0.05). There was no significant difference for the conventional and functional strength ratio for knee and hip joint between the two groups (p > 0.05).
Soccer players with anterior pelvic tilt demonstrated a higher hamstring flexibility and less extended hip flexion during the late stages of late swing phase while sprinting in comparison with players without anterior pelvic tilt. It should be noted that while measuring the hamstring flexibility the initial pelvic tilt angle can contribute to the amount of flexibility displayed by the athletes and thus should be taken into consideration. Furthermore smaller amount of hip flexion prior to ground contact can be analyzed performance-wise due to the fact that it would reduce the amount of stride length. However further research is needed to understand the effect of smaller hip flexion on different aspects of sprinting.
When assessing the hamstring flexibility the amount of pelvic tilt should be taken into account as it is associated with amount of hamstring flexibility. Anterior pelvic tilt should also be noted as it reduces the amount of hip flexion at the end stages of the late swing phase which may have performance and injury implications during sprint.