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Tatiane Gorski, Thomas Rosser, Hans Hoppeler and Michael Vogt

Purpose:

To describe the development of anthropometric and physical characteristics of young Swiss alpine skiers between 2004 and 2011, to compare them between age and performance-level groups, and to identify age- and sex-dependent reference values for the tests performed.

Methods:

The Swiss-Ski Power Test includes anthropometric measures and physical tests for coordination and speed, strength, anaerobic capacity, and endurance. The authors analyzed the results of 8176 tests performed by 1579 male and 1109 female alpine skiers between 2004 and 2011. Subjects ranged between regional and national level of performance and were grouped according to their competition age groups (U12, 11 y; U14, 12–13 y; U16, 14–15 y; U18, 16–17 y; U21, 18–20 y) and performance level.

Results:

A progressive increase in anthropometric measures and improvements in tests results with increasing age were found. For all tests, male athletes had better results than female athletes. Minor differences were observed in anthropometric characteristics between 2004 and 2011 (mostly <5%), while results of physical and coordinative tests showed significant improvements (up to more than 50% enhancement) or stability over the years. Differences between higher- and lower-level athletes were more pronounced in tests for lower-limb strength and anaerobic capacity.

Conclusions:

The presented profile of young Swiss alpine skiers highlights the improvements in different physical aspects along the maturation process and chronologically over a period of 7 y. Furthermore, reference values are provided for comparisons with alpine skiers or athletes from other sports.

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Paul G. Taylor, Raul Landeo and Jennifer Coogan

The purpose of this study was to explore movement variability of throwing arm and ball release parameters during the water polo shot and to compare variability between successful (hit) and unsuccessful (miss) outcomes. Seven injury free, subelite, females completed 10 trials of the 5 m water polo penalty shot. Intraindividual coefficient of variation percentage (CV%) values were calculated for elbow and wrist angular displacement, wrist linear velocity and ball release parameters (height, angle and velocity). Coordination variability (elbow/wrist angular displacement) was calculated as the CV% of the mean cross-correlation coefficient. Elbow and wrist displacement variability decreased to 80% of throwing time then increased toward release. Wrist linear velocity variability reduced toward release. Individual CV% values ranged between 1.6% and 23.5% (all trials), 0.4% and 20.6% (hit), and 0.4% and 27.1% (miss). Ball release height and velocity variability were low (< 12%; all trials) whereas release angle variability was high (>27%; all trials). Cross-correlation results were inconclusive. Roles of the elbow and wrist in production of stable ball release height and velocity and control of the highly variable release angle in the water polo shot are discussed and suggested for further study. Optimal levels of variability warrant future investigation.

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Travis J. Peterson, Rand R. Wilcox and Jill L. McNitt-Gray

Our aim was to determine how skilled players regulate linear and angular impulse while maintaining balance during the golf swing. Eleven highly-skilled golf players performed swings with a 6-iron and driver. Components contributing to linear and angular impulse generated by the rear and target legs (resultant horizontal reaction force [RFh], RFh-angle, and moment arm) were quantified and compared across the group and within a player (α = .05). Net angular impulse generated by both the rear and target legs was greater for the driver than the 6-iron. Mechanisms used to regulate angular impulse generation between clubs varied across players and required coordination between the legs. Increases in net angular impulse with a driver involved increases in target leg RFh. Rear leg RFh-angle was maintained between clubs whereas target leg RFh became more aligned with the target line. Net linear impulse perpendicular to the target line remained near zero, preserving balance, while net linear impulse along the target line decreased in magnitude. These results indicate that the net angular impulse was regulated between clubs by coordinating force generation of the rear and target legs while sustaining balance throughout the task.

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John Cairney, John A. Hay, Brent E. Faught, Andreas Flouris and Panagiota Klentrou

It is not known whether children with Developmental Coordination Disorder (DCD) have lower cardiorespiratory fitness (CRF) than children without the disorder, or whether this relationship varies by age and gender. These issues are examined using a cross-sectional assessment of children 9-14 years of age (N = 549). Participants were screened for DCD using the short form Bruininks-Oseretsky Test of Motor Proficiency (BOTMP-SF). A BOTMP-SF age-adjusted standard score at or below the 10th percentile rank on the BOTMP-SF was required to classify a diagnosis for probable DCD. CRF was determined from each participant’s predicted peak-aerobic power using the Léger 20-m shuttle-run test. Children with DCD report lower CRF than children without the disorder and are more likely to be in a high-risk group (≤ 20th percentile in peak VO2). Moreover, 70% of boys with DCD scored at or below the 20th percentile in peak VO2. Further research in a laboratory setting should be conducted to confirm these findings.

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Sarah Astill and Andrea Utley

This study investigated the nature and extent of inter and intralimb coupling of the upper limbs in children with developmental coordination disorder (DCD) and their age-matched controls (AMC) when catching a ball two-handed. Sixteen children (8 DCD, 8 AMC) volunteered for the study; parental consent was gained for each child. Using standard video analysis and 3D kinematic analysis, all children were examined performing 30 two-handed catches. Video analysis showed that the AMC children caught more balls than the DCD children (p ≤ .005). Analyses of the kinematic data showed DCD participants exhibit a greater degree of linkage both between and within limb than the AMC participants (p ≤ .01), but the AMC participants demonstrate more intra individual variability in these linkages (p ≤ .01). The data shows that both DCD and AMC children couple their limbs to exert control over redundant degrees of freedom when catching a ball two-handed. However, DCD children show little capacity to vary their motor behavior exhibiting a less adaptable movement system, which in turn affects their success at the task.

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Martine H.G. Verheul and Reint H. Geuze

Rhythmic interlimb coordination arises from the interaction of intrinsic dynamics and behavioral information, that is, intention, memory, or external information specifying the required coordination pattern. This study investigates the influence of the content of memorized behavioral information on coordination in musically experienced and inexperienced participants. These groups are hypothesized to have different intrinsic dynamics for this task. Stability was assessed in a switching task (variability and switching time). The in-phase, antiphase, and 90°-phase difference were specified in a neutral and an ecologically relevant manner. Musicians showed more stable coordination than nonmusicians did. No interaction effect was found with memorized behavioral information. Behavioral information showed an interaction effect with phase pattern on coordination variability, with the strongest effect for the 90°-phase pattern. Switching time was affected largely in line with the findings for coordination variability. Participants showed an intraindividual preference for one type of gallop and one type of switch strategy, suggesting different hand roles.

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Hayri Baran Yosmaoglu, Gül Baltaci, Defne Kaya and Hamza Ozer

Context:

The development pattern of motor coordination, strength, and functional ability during recovery from anterior cruciate ligament (ACL) reconstruction.

Objective:

To investigate the relationship between motor coordination, functional ability, and strength after ACL reconstruction.

Design:

Prospective clinical follow-up study.

Setting:

Sports-injury research laboratory.

Participants:

20 subjects who underwent ACL reconstruction.

Interventions:

Real-time eccentric and concentric motor coordination were tested by a multijoint lower limb tracking-trajectory test, quadriceps and hamstring isokinetic strength were assessed by isokinetic dynamometer, and functional performance was tested with a single-leg-hop test 6 and 12 mo after ACL reconstruction.

Main Outcome Measures:

Percentage deficits of the involved lower extremity for target-tracking ability, peak torque, total work parameters of isokinetic strength, and single-leg-hop distance.

Results:

Deficits in hamstring–quadriceps isokinetic muscle strength and single-leg-hop distance significantly decreased from the 6th to the 12th mo after surgery (P < .05). There were no significant differences in muscle concentric and eccentric motor-coordination deficits of the involved side (P > .05).

Conclusions:

Although muscle strength and functional performance clearly increased from the 6th to the 12th mo after surgery, coordination characteristics of involved side remained low. This pattern demonstrated that motor-coordination progression was not affected by strength development. Patients continued to have significant motor-coordination deficits even 12 mo postsurgery. Therefore, the authors recommend that neuromuscular-coordination exercises be included in long-term rehabilitation programs to improve motor coordination.

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Hiroko Tanabe, Keisuke Fujii and Motoki Kouzaki

We aimed to investigate joint coordination of lower limbs in dancers during tiptoe standing and the relationship between joint coordination and muscle coactivation. Seven female ballet dancers performed tiptoe standing with six leg positions (fi e classical dance positions and one modern dance position) for 10 s. The kinematic data of the metatarsophalangeal (MP), ankle, knee, and hip joints was collected, and surface electromyography (EMG) of over 13 lower limb muscles was conducted. Principal component analysis was performed to determine joint coordination. MP–ankle and ankle–knee had in-phase coordination, whereas knee–hip showed anti-phase coordination in the sagittal plane. In addition, most EMG–EMG coherence around the MP and ankle joints was significant up to 50 Hz when these two joints swayed with in-phase. This suggests that different joint coordination patterns are associated with neural processing related to different muscle coactivation patterns. In conclusion, ballet dancers showed in-phase coordination from the MP to knee joints, which was associated with muscle coactivation to a higher frequency domain (up to 50 Hz) in comparison with anti-phase coordination.

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Jonathan Leo Ng, Chris Button, Dave Collins, Susan Giblin and Gavin Kennedy

movement solutions and/or may not adapt these solutions well ( Ng & Button, 2018 ). Movement attributes are key (basic) features of motor control, such as posture and coordination of limbs, which are typically nested and required to be used synchronously in most activities ( Glazier & Davids, 2009

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M.J.M. Volman and Reint H. Geuze

The stability of single and bimanual (i.e., in-phase and antiphase) rhythmic finger movements was studied in 24 children with a developmental coordination disorder (DCD) and 24 matched controls from a dynamic pattern perspective. Stability was assessed by applying perturbations and measuring the time the system needed to return to its initial stability (i.e., the relaxation time). In addition, fluctuations of the patterns were measured. For antiphase coordination patterns, the frequency at which loss of stability occurred was also determined. Children with DCD displayed less stable single and bimanual rhythmic coordination patterns than control children. Further, within the DCD group, 9 children were identified as having particularly poor bimanual coordination stability. Individual differences suggested that variability of individual limb oscillations might have contributed to this poorer interlimb coordination stability. Findings were discussed in relation to a previous study on DCD in which the Wing-Kristofferson timekeeper model was applied.