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Christopher Joyce, Angus Burnett, and Miccal Matthews

No method currently exists to determine the location of the kick point during the golf swing. This study consisted of two phases. In the first phase, the static kick point of 10 drivers (having identical grip and head but fitted with shafts of differing mass and stiffness) was determined by two methods: (1) a visual method used by professional club fitters and (2) an algorithm using 3D locations of markers positioned on the golf club. Using level of agreement statistics, we showed the latter technique was a valid method to determine the location of the static kick point. In phase two, the validated method was used to determine the dynamic kick point during the golf swing. Twelve elite male golfers had three shots analyzed for two drivers fitted with stiff shafts of differing mass (56 g and 78 g). Excellent between-trial reliability was found for dynamic kick point location. Differences were found for dynamic kick point location when compared with static kick point location, as well as between-shaft and within-shaft. These findings have implications for future investigations examining the bending behavior of golf clubs, as well as being useful to examine relationships between properties of the shaft and launch parameters.

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Ashley J. Cripps, Luke Hopper, and Christopher Joyce

Purpose:

To confirm the effect of maturational differences on anthropometric and physical testing and explore the effect of maturation on technical skill and coaches’ perceptions of skill in adolescent Australian footballers.

Methods:

Athletes were recruited from a semielite under 16 competition (n = 94, age 15.7 ± 0.3 years) and completed anthropometric, physical, and technical skill tests. Coaches from each team provided subjective ratings of athletes’ technical skills. Maturation groups were derived from years from peak height velocity estimates, with classifications either later, average or earlier maturing.

Results:

Effect size comparisons revealed very large to moderate effects between groups for anthropometric measures and performance in sprint and jump tasks. Small to moderate effects were reported between groups for coaches’ perceptions of skill, with the earlier maturing group perceived to have better overall technical skills, marking and ball winning abilities. Small to trivial effects were reported for performance in the technical skill tests.

Conclusion:

Despite no differences in skill tests, earlier maturing athletes may be afforded significant selection and competition advantages due to advanced physical capacities and coaches’ perceptions of skill.

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Tzu-Chieh Liao, Joyce H. Keyak, and Christopher M. Powers

The primary purpose of this study is to determine whether recreational runners with patellofemoral pain (PFP) exhibit greater peak patella cartilage stress compared with pain-free runners. A secondary purpose was to determine the kinematic and/or kinetic predictors of peak patella cartilage stress during running. A total of 22 female recreational runners (12 with PFP and 10 pain-free controls) participated in this study. Patella cartilage stress profiles were quantified using subject-specific finite element models simulating the maximum knee flexion angle during the stance phase of running. Input parameters to the finite element model included subject-specific patellofemoral joint geometry, quadriceps muscle forces, and lower-extremity kinematics in the frontal and transverse planes. Tibiofemoral joint kinematics and kinetics were quantified to determine the best predictor of stress using stepwise regression analysis. Compared with the pain-free runners, those with PFP exhibited greater peak hydrostatic pressure (PFP vs control: 21.2 [5.6] MPa vs 16.5 [4.6] MPa) and maximum shear stress (PFP vs control: 11.3 [4.6] MPa vs 8.7 [2.3] MPa). Knee external rotation was the best predictor of peak hydrostatic pressure and peak maximum shear stress (38% and 25% of variances, respectively), followed by the knee extensor moment (21% and 25% of variances, respectively). Runners with PFP exhibit greater peak patella cartilage stress during running compared with pain-free individuals. The combination of knee external rotation and a high knee extensor moment best predicted the elevated peak stress during running.

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Mikayla J. Lyons, Jennifer Conlon, Amy Perejmibida, Paola Chivers, and Christopher Joyce

Purpose: This study examined the maintenance of passing performance following soccer-specific high-intensity intermittent exercise in elite (n = 9) and subelite (n = 11) Western Australian female soccer players (19.5 [2.5] y). Methods: A total of 20 participants completed the Loughborough Soccer Passing Test (LSPT) prior to, during, and following 90 minutes of a modified, female-specific, individualized exercise protocol (Loughborough Intermittent Shuttle Test [LIST]) to simulate 2 halves of a soccer match. Performance in the LSPT was calculated by adding “raw time” to the accumulated “penalty time” for each test. Results: Elite players recorded greater distances (t 58 = 4.671, P < .001, effect size [ES] = 1.21) and higher derived VO2max values (t 58 = 4.715, P < .001, ES = 1.20) for the LIST exercise protocol over the subelite players. The total performance times for each LSPT were longer in the subelites in comparison with the elites, with a very large ES difference seen in post-LIST1 (t 18 = −6.64, P < .001, ES = 2.99) and post-LIST2 (t 18 = −9.143, P < .001, ES = 4.12). No between-groups differences were identified for “raw time” at any time point. Hence, all reported LSPT performance differences are attributed to “penalty time.” Conclusion: These data suggest that elite players can sustain their passing performance more efficiently throughout match play that can subelite female soccer players. These findings may contribute to future talent-identification testing by helping to distinguish between elite- and subelite-level players through sustained passing performance. Coaches may also use this information to better inform best-practice training methods through modification of male soccer-specific high-intensity intermittent exercise to a female cohort.

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Damien M. Hess, Christopher J. Joyce, Brent L. Arnold, and Bruce M. Gansneder

Context:

Agility training has been proposed as an important tool in rehabilitation. However, it is unclear which types of agility training are most useful.

Objective:

To assess the effects of agility training on balance in individuals with functionally unstable ankles.

Design:

A 2-group experimental design with repeated measures.

Setting:

Laboratory.

Patients:

Twenty college-aged volunteers, each with 1 functionally unstable ankle, were randomly assigned to 1 of 2 groups.

Interventions:

Subjects in the experimental group performed agility training 3 times per week for 4 weeks.

Main Outcome Measures:

Subjects were tested for static single-leg balance before and after the training period. Anterior/posterior sway amplitude, medial/lateral sway amplitude, and sway index were assessed using the Chattex Balance System.

Results:

No significant differences in balance were found after the agility training.

Conclusions:

Agility training did not improve static single-leg balance in subjects with functionally unstable ankles.