Enhancing foot velocity in football kicking: the role of strength training.

In all codes of football, it is advantageous to be able to achieve a high ball speed or distance in a kick. An important determinant of ball speed and kick distance is the velocity of the foot at impact with the ball. Therefore, it is of interest to strength and conditioning practitioners to identify training programs that can increase foot velocity. The purpose of this review is to identify the factors influencing kicking performance and the research evidence relating to resistance training designed to enhance foot velocity in kicking. The review has been divided into 3 main sections. The first addresses the biomechanics of kicking to provide insights into the physical demands. The second section reviews the relationships between various measures of strength with performance indicators of maximum kicking, and the third part explores the research investigating the effects of resistance training on maximum kicking performance. Kicking can be described as a skill involving proximal-to-distal muscle activation. Foot velocity is determined by a complex sequencing of hip flexor and knee extensor concentric contractions and also involves hip extensor and knee flexor activation to assist with movement control. Research reporting correlations between strength and kicking performance support the importance of hip flexor and quadriceps strength. Although unclear, there is some evidence that adequate strength of the support leg, trunk muscles, hip adductors, and the muscles that control pelvic rotations are important. Strength training studies have shown that foot velocity and kicking performance can be enhanced by supplementary programs to regular football training, especially in nonelite athletes. Potentially valuable training includes plyometrics, exercises that simulate the whole kicking action, and kicking weighted balls. Exercises that isolate parts of the kicking action are not recommended because these do not appear to transfer well to kicking performance. There are many unanswered questions that await future research.

Fast bowling arm actions and the illegal delivery law in men's high performance cricket matches.

This study investigated the bowling arm kinematics of 21 elite fast bowlers (mean +/- SD; age = 27.8 +/- 3.9 years) while performing in test, tour and one day international matches. Thirty-one of the 34 deliveries analysed exhibited straightening at the elbow joint (straightening min = 3 degrees, max = 22 degrees, mean +/- SD = 9 +/- 5 degrees), which by strict definition in the 2000 laws of cricket made them illegal. Five deliveries from three bowlers exhibited hyperextension of the bowling elbow (19 +/- 5 degrees). When assessed against an arbitrary threshold of 15 degrees for elbow straightening, ball speeds for deliveries above this threshold (39.5 +/- 2.0 m/s) were significantly faster (effect size = 1.4; p = 0.006) than deliveries below it (37.1 +/- 1.4 m/s). When grouped by delivery length, the bouncers and short deliveries recorded more elbow straightening (12 +/- 6.6 degrees) than the good length deliveries (9 +/- 4.4 degrees) and the full deliveries (8 +/- 5.7 degrees), although these were not statistically significant differences. The results of this study support the implementation of a tolerance threshold for assessing the legality of fast bowling actions. Further research is recommended into in-match kinematic modelling, laboratory based assessments of illegal bowling actions, perceptual aspects of bowling actions and remedial methods to reduce elbow straightening in bowling actions.

Are anthropometric and kinematic parameters of the lumbo-pelvic-hip complex related to running injuries?

The purpose of the experiment was to test whether specific anthropometric or kinematic parameters of the lumbo-pelvic-hip complex were related to running injuries. A case-control design was used to compare a group of 22 runners with a history of injury within the previous 12 months to a group of 19 injury-free controls. All runners were pain-free at the time of measurement. Groups were matched for self-reported average running volume per week and average number of running sessions per week. Anthropometric and kinematic parameters, previously speculated as being related to running injuries, were selected for evaluation. Running trials were conducted on a treadmill at a speed of 4.0 m/sec. The three-dimensional angular rotations of the lumbar spine, pelvis, and hip during running were measured using a VICON motion analysis system with seven cameras operating at a sampling rate of 200 Hz. None of the measured anthropometric or kinematic parameters were found to be significantly different between the injured and control groups. Despite the theoretical rationale, no evidence was found in the current experiment demonstrating a clear relationship between anthropometric or kinematic parameters of the lumbo-pelvic-hip complex and running injuries.

Intra-subject repeatability of the three dimensional angular kinematics within the lumbo-pelvic-hip complex during running.

The intra-subject repeatability of measuring the three dimensional (3D) angular kinematics of the lumbo-pelvic-hip complex during running was evaluated. Spatio-temporal parameters were found to be repeatable. All angular kinematic parameters displayed high within-day repeatability despite numerous potential sources of variability in the data. Most angular kinematic parameters also displayed high between-day and overall repeatability, except for trunk flexion-extension, lumbar spine flexion-extension, pelvic anterior-posterior tilt, hip axial rotation and thigh axial rotation. These angular parameters were highly susceptible to marker reapplication errors that produced static daily offsets in the data. Overall, the results of this study suggest that the 3D angular kinematic patterns of the lumbo-pelvic-hip complex during running can be measured with sufficient repeatability to justify the implementation of the method as an evaluation tool in future investigations. However, caution must be exerted when interpreting the absolute magnitudes of trunk flexion-extension, lumbar spine flexion-extension, pelvic anterior-posterior tilt, hip axial rotation and thigh axial rotation, given the poor level of repeatability found for these measures.