Cutting maneuvers performed without adequate planning may increase the risk of noncontact knee ligament injury due to the increased external varus/valgus and internal/external rotation moments applied to the knee. These results are probably due to the small amount of time to make appropriate postural adjustments before performance of the task, such as the position of the foot on the ground relative to the body center of mass. Subsequently, training for the game situation should involve drills that familiarize players with making unanticipated changes of direction. Practice sessions should also incorporate plyometrics and should focus on better interpretation of visual cues to increase the time available to preplan a movement.

Compared with running, the potential for increased ligament loading during sidestepping and crossover cutting maneuvers is a result of the large increase in varus/valgus and internal/external rotation moments rather than any change in the external flexion moment. The combined external moments applied to the knee joint during stance phase of the cutting tasks are believed to place the ACL and collateral ligaments at risk of injury, particularly at knee flexion angles between 0 degrees and 40 degrees, if appropriate muscle activation strategies are not used to counter these moments.

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Understanding the magnitude of forces and lower body kinematics that occur during a change of direction (COD) task can provide information about the biomechanical demands required to improve performance. To compare the magnitude of force, impulse, lower body kinematics and post-COD stride velocity produced between athletes of different strength levels during a COD task, 12 stronger (8 males, 4 females) and 12 weaker (4 males, 8 females) recreational team sport athletes were recruited. Strength levels were determined by relative peak isometric force of the dominant and non-dominant leg. All athletes performed 10 pre-planned 45° changes of direction (5 left, 5 right) while three-dimensional motion and ground reaction force (GRF) data were collected. Differences in all variables for the dominant leg were examined using a one-way analysis of variance (ANOVA) with a level of significance set at p ≤0.05. The stronger group displayed significantly faster post-COD stride velocity and greater vertical and horizontal braking forces, vertical propulsive force, vertical braking impulse, horizontal propulsive impulse, angle of peak braking force application, hip abduction and knee flexion angle compared to the weaker group. The results suggest that individuals with greater relative lower body strength produced higher magnitude plant foot kinetics and modified lower body positioning while producing faster COD performances. Future investigations should determine if strength training to enable athletes to increase plant foot kinetics while maintaining or adopting a lower body position results in a concomitant increases in post-COD stride velocity.

Background: A high level of participant skill is influential in determining the outcome of many sports. Thus, tests assessing skill outcomes in sport are commonly used by coaches and researchers to estimate an athlete's ability level, evaluate the effectiveness of interventions or for the purpose of talent identification.Objective: The objective of this systematic review was to examine the methodological quality, measurement properties and feasibility characteristics of sporting skill outcome tests reported in the peer-reviewed literature.Data Sources: A search of both SPORTDiscus and MEDLINE databases was undertaken.Study Selection: Studies that examined tests of sporting skill outcomes were reviewed. Only studies that investigated measurement properties of the test (reliability or validity) were included. A total of 22 studies met the inclusion/exclusion criteria. Study Appraisal and Synthesis Methods:A customised checklist of assessment criteria, based on previous research, was utilised for the purpose of this review.Results: A range of sports were the subject of the 22 studies included in this review, with considerations relating to methodological quality being generally well-addressed by authors.A range of methods and statistical procedures were used by researchers to determine the measurement properties of their skill outcome tests. The majority (95%) of the reviewed studies investigated test-retest reliability, and where relevant, inter and intra-rater reliability was also determined. Content validity was examined in 68% of the studies, with most tests investigating multiple skill domains relevant to the sport. Only 18% of studies assessed all three reviewed forms of validity (content, construct and criterion) with just 14% investigating iii Tests examining skill outcomes in sport the predictive validity of the test. Test responsiveness was reported in only 9% of studies, whilst feasibility received varying levels of attention. Limitations:In organised sport, further tests may exist which have not been investigated in this review. This could be due to such tests firstly, not being published in the peer-review literature and secondly, not having their measurement properties (i.e. reliability or validity) examined formally. Conclusions:Of the 22 studies included in this review, items relating to test methodological quality were on the whole, well addressed. Test-retest reliability was determined in all but one of the reviewed studies, whilst most studies investigated at least two aspects of validity (i.e. content, construct or criterion-related validity). Few studies examined predictive validity or responsiveness. While feasibility was addressed in over half of the studies, practicality and test limitations were rarely addressed. Consideration of study quality, measurement properties and feasibility components assessed in this review can assist future researchers when developing or modifying tests of sporting skill outcomes.

Balance training produced reductions in peak valgus and internal rotation moments, which could lower ACL injury risk during sporting maneuvers. Strength training tended to increase the applied knee loading known to place strain on the ACL, with the free weights group also decreasing the amount of knee flexion. It is recommended that balance training be implemented because it may reduce the risk of ACL injury.

Anterior cruciate ligament (ACL) injury rates have increased by ∼50% over the last 10 years. These figures suggest that ACL focused research has not been effective in reducing injury rates among community level athletes. Training protocols designed to reduce ACL injury rates have been both effective (n = 3) and ineffective (n = 7). Although a rationale for the use of exercise to reduce ACL injuries is established, the mechanisms by which they act are relatively unknown. This article provides an injury prevention framework specific to noncontact ACL injuries and the design of prophylactic training protocols. It is also apparent that feedback within this framework is needed to determine how biomechanically relevant risk factors like peak joint loading and muscular support are influenced following training. It is by identifying these links that more effective ACL injury prevention training programs can be developed, and, in turn, lead to reduced ACL injury rates in the future.

T he pu r p o s e of t h i s s t ud y wa s t o p e r for m a de t a i l e d k i ne mat i c , k i ne t i c , a ndelectromyographic comparison of maximal effort horizontal and vertical jumping. It was of particular interest to identify factors responsible for the control of jump direction. Eight male subjects performed maximal horizontal jumps (HJ) and vertical jumps (VJ) from a standing posture with a counter movement. Three-dimensional motion of the trunk, pelvis, and bilateral thigh, shank, and foot segments were recorded together with bilateral ground reaction forces and electromyographic (EMG) activity from seven right leg muscles. Relative to the VJ, the trunk is displaced further forward at the beginning of the HJ, through greater ankle joint dorsiflexion and knee extension. The activity of the biarticular rectus femoris and hamstrings were adapted to jump direction and helped to tune the hip and knee joint torques to the requirements of the task. The primary difference in joint torques between the two jumps was for the knee joint, with the extension moment reduced in the HJ, consistent with differences in activation levels of the biarticular rectus femoris and hamstrings. Activity of the mono-articular knee extensors was adapted to jump direction in terms of timing rather than peak amplitude. Overall results of this study suggest that jump direction is controlled by a combination of trunk orientation at the beginning of the push-off and the relative activation levels of the biarticular rectus femoris and hamstring muscles during the push-off. simulation model that realistic horizontal jumps may be achieved using the muscle stimulation patterns from a vertical jump by simply rotating the body mass forward in relation to the base of support prior to extending the legs. The authors referred to this as a rotation-extension strategy. Results suggested that the required adaptations to the net joint moments that occur when jumping forward compared to upward can be produced by intrinsic muscle properties alone (ie. stiffness and damping). This simplifies the neural control of tasks such as jumping because the same muscle stimulation is effective, although not optimal, for a range of jump directions.In a comparison of countermovement jumps performed in different directions, Jones and Caldwell (2003) explored hypotheses concerning the role of mono-articular and bi-articular muscles. It was hypothesized that bi-articular muscle activity would be modulated to control the direction of the ground reaction force for jumps in different directions, whereas mono-articular muscle activity would not be affected by jump direction. These hypotheses are based on the idea that bi-articular muscles are activated to tune the distribution of moments amongst joints in order to meet task requirements (Jacobs and Ingen Schenau, 1992), whereas mono-articular muscles are activated when they can contribute positive work at the joint they span (Jacobs, Bobbert & van Ingen Schenau, 1993). While Jones and Caldwell (2003) showed activity of ...