CAN THE SPLIT-STEP CUTTING TECHNIQUE REDUCE LOADING AND MAINTAIN PERFORMANCE?

INTRODUCTION: Cutting (evasive running) movements are integral to performance in many field- and court-based sports but have been associated with lower limb injuries. This injury risk is attributed to a combination of lower limb geometry and high forces acting together to stress anatomical structures, particularly at the ankle and knee joint. Alternative positioning of the stance foot and adjusted orientation of the lower limbs through changes to the cutting technique may reduce loading (e.g. Besier et al., 2001) but technique interventions for cutting have not been explicitly investigated in-depth. Therefore, the aim of this study was to compare the biomechanical characteristics of unplanned side-step (single foot contact) and split-step (double foot contact) cutting techniques, particularly relating to lower limb loading and ground reaction impulses generated during the primary cutting step. It was expected that the split-step would reduce joint loading and maintain performance requirements

Control strategy for a hand balance

The goal of this study was to investigate the control strategy employed by gymnasts in maintaining a hand balance. It was hypothesized that a “wrist strategy” was used in which perturbations in the sagittal plane were corrected using variations in wrist flexor torque with synergistic shoulder and hip torques acting to preserve a fixed body configuration. A theoretical model of wrist strategy indicated that control could be effected using wrist torque that was a linear function of mass center displacement and velocity. Four male gymnasts executed hand balances and 2-dimensional inverse dynamics was used to determine net joint torque time histories at the wrist, shoulder, and hip joints in the sagittal plane. Wrist torque was regressed against mass center position and velocity values at progressively earlier times. It was found that all gymnasts used the wrist strategy, with time delays ranging from 160 to 240 ms. The net joint torques at the shoulder and hip joints were regressed against the torques required to maintain a fixed configuration. This fixed configuration strategy accounted for 86% of the variance in the shoulder torque and 86% of the variance in the hip torque although the actual torques exceeded the predicted torques by 7% and 30%, respectively. The estimated time delays are consistent with the use of long latency reflexes, whereas the role of vestibular and visual information in maintaining a hand balance is less certain

DEVELOPMENT AND EVALUATION OF A METHOD TO QUANTIFY RUGBY PLACE KICK PERFORMANCE FROM INITIAL BALL FLIGHT DATA

The purpose of this study was to develop and evaluate a method for quantifying rugby place kick performance using a metric that represents field-based performance but relies only on data typically available within a laboratory setting. A mathematical model was developed to predict the flight path of a rugby ball using equations of projectile motion and initial ball flight kinematics as inputs. The accuracy of the model predictions were then evaluated against empirical data collected from eight place kicks taken 22 m from the goalposts on a rugby pitch. The model estimated the position of the ball at the instant it reached the goalposts with a root mean square error of 0.65 m (2.9% of the range). It is intended that this method will provide an applied outcome measure that is relevant to players and coaches

Bend sprinting performance : new insights into the effect of running lane

Athletes in inner lanes may be disadvantaged during athletic sprint races containing a bend portion because of the tightness of the bend. We empirically investigated the veracity of modelled estimates of this disadvantage and the effect of running lane on selected kinematic variables. Three-dimensional video analysis was conducted on nine male athletes in lanes 8, 5 and 2 of the bend of an outdoor track (radii: 45.10, 41.41 and 37.72 m, respectively). There was over 2% (p < 0.05) reduction in mean race velocity from lane 8 (left step 9.56 ± 0.43 m/s, right step: 9.49 ± 0.41 m/s) to lane 5 (left step: 9.36 ± 0.51 m/s, right step: 9.30 ± 0.51 m/s), with only slight further reductions from lane 5 to lane 2 (left step: 9.34 ± 0.61 m/s, right step: 9.30 ± 0.63 m/s). Race velocity decreased mainly because of reductions in step frequency as radius decreased. These unique data demonstrate the extent of the disadvantage of inner lane allocation during competition may be greater than previously suspected. Variations in race velocity changes might indicate some athletes are better able to accommodate running at tighter radii than others, which should have implications for athletes' training

A BIOMECHANICAL ANALYSIS OF THE KICKING LEG DURING A RUGBY PLACE KICK

The successful performance of rugby place kicks is often important in determining the outcome of a match. This study aimed to further the understanding of rugby place kicking technique by quantifying and explaining kicking leg joint mechanics. Three-dimensional joint kinematics and kinetics were calculated using an inverse dynamics analysis. Whilst ankle motion was negligible, the knee flexed until around 50% of the kicking phase before extending towards ball contact. A resultant hip flexor moment was largely dominant throughout; it initally reduced extension before initiating flexion near support foot contact. Whilst these patterns were broadly similar to soccer kicking, peak magnitudes of angular velocity and resultant moment appeared to differ from soccer kicking and, along with the mechanics about other joint axes, these require further investigation

THE DIFFERENCES IN RUGBY PLACE KICK TECHNIQUE BETWEEN SUCCESSFUL AND LESS SUCCESSFUL KICKERS

This study aimed to understand the differences in technique between groups of rugby place kickers who achieve different performance outcomes. Thirty kickers were analysed using 3D motion capture and grouped as long (successful), wide-left or short (both less successful). The long kickers achieved a faster ball velocity than the short kickers by doing more positive hip flexor and knee extensor work. The long and wide-left kickers achieved comparable ball velocities, but used different strategies. The long kickers did more positive knee extensor work whereas the wide-left kickers did more positive hip flexor work, facilitated by a ‘tension arc’ achieved through pelvis-thorax rotation. Although the ‘tension arc’ may be beneficial for the generation of ball velocity magnitude, rugby place kicking coaches should be wary of its use due to its negative effect on accuracy

A joint kinetic analysis of rugby place kicking technique to understand why kickers achieve different performance outcomes

We aimed to identify differences in kicking leg and torso mechanics between groups of rugby place kickers who achieve different performance outcomes, and to understand why these features are associated with varying levels of success. Thirty-three experienced place kickers performed maximum effort place kicks, whilst three-dimensional kinematic (240 Hz) and ground reaction force (960 Hz) data were recorded. Kicking leg and torso mechanics were compared between the more successful (‘long’) kickers and two sub groups of less successful kickers (’short’ and ‘wide-left’) using magnitude-based inferences and statistical parametric mapping. Short kickers achieved substantially slower ball velocities compared with the long kickers (20.8 ± 2.2 m/s vs. 27.6 ± 1.7 m/s, respectively) due to performing substantially less positive hip flexor (normalised mean values = 0.071 vs. 0.092) and knee extensor (0.004 vs. 0.009) joint work throughout the downswing, which may be associated with their more front-on body orientation, and potentially a lack of strength or intent. Wide-left kickers achieved comparable ball velocities (26.9 ± 1.6 m/s) to the long kickers, but they were less accurate due to substantially more longitudinal ball spin and a misdirected linear ball velocity. Wide-left kickers created a tension arc across the torso and therefore greater positive hip flexor joint work (normalised mean = 0.112) throughout the downswing than the long kickers. Whilst this may have assisted kicking foot velocity, it also induced greater longitudinal torso rotation during the downswing, and may have affected the ability of the hip to control the direction of the foot trajectory

UNDERSTANDING ELITE SPRINT START PERFORMANCE THROUGH AN ANALYSIS OF JOINT KINEMATICS

This study aimed to investigate how leg kinematics contribute to the performance, in terms of external horizontal power production, of three elite sprinters during the block and first step phases of a sprint. The highest block phase power was produced by sprinter B, who exhibited the greatest hip extension, particularly at the rear leg. Sprinter A achieved a higher horizontal block exit velocity, however, this appeared to be due to a longer push duration rather than greater average force production. The highest horizontal power during the first stance was again produced by sprinter B, who exhibited the greatest total stance leg joint extension. The other two sprinters exhibited similar leg extension to each other. However, sprinter A was able to generate greater horizontal power, which may have been due to his centre of mass being further in front of his foot at touchdown

BEND SPRINTING AT DIFFERENT RADII OF AN OUTDOOR ATHLETICS TRACK

Athletes in the inners lanes may be at a disadvantage during sprint races that contain a bend portion. This study investigated the effect on performance when sprinting on the different radii of an outdoor track. There was an approximately 2% reduction in mean race velocity from lane 8 (left step: 9.56 m/s, right step: 9.49 m/s) to lane 5 (left step: 9.36 m/s, right step: 9.30 m/s), with only slight further reductions from lane 5 to lane 2 (left step: 9.34 m/s, right step: 9.30 m/s). This was mainly due to reductions in step frequency as radius decreased. The disadvantage of the inner lane compared to the outer lane may be greater than previously suspected. Larger race velocity standard deviations as radius decreased may be indicative of athletes being differently able to accommodate running at tighter radii than others. This may have implications for training and competition