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Kristin E. Meyer, Erin E. Saether, Emily K. Soiney, Meegan S. Shebeck, Keith L. Paddock and Paula M. Ludewig

Proper scapular motion is crucial for normal shoulder mechanics. Scapular motion affects glenohumeral joint function during throwing, yet little is known about this dynamic activity. Asymptomatic subjects (10 male and 10 female), ages 21 to 45, were analyzed. Electromagnetic surface sensors on the sternum, acromion, and humerus were used to collect 3-D motion data during three trials of low-velocity throwing. Scapular angular position data were described for five predetermined events throughout the throw corresponding with classic descriptions of throwing phases, and trial-to-trial reliability was determined. ANOVA compared scapular angles across events. Subjects demonstrated good to excellent reliability between trials of the throw (ICC 0.74–0.98). The scapula demonstrated a pattern of external rotation, upward rotation (peak of approx. 40°), and posterior tilting during the initial phases of the throw, progressing into internal rotation after maximum humeral horizontal abduction. During the arm acceleration phase, the scapula moved toward greater internal rotation and began anteriorly tilting. At maximum humeral internal rotation, the scapula ended in internal rotation (55°), upward rotation (20°), and anterior tilting (3°).

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Rodrigo de Marche Baldon, Daniel Ferreira Moreira Lobato, Lívia Pinheiro Carvalho, Paulo Roberto Pereira Santiago, Benedito Galvão Benze and Fábio Viadanna Serrão

The purposes of this study were to compare lower-limb kinematics between genders, and determine the relationships among eccentric hip abductor and lateral rotator torques and lower-limb kinematics. The movements of the pelvis, femur, and knee were calculated for 16 women and 16 men during the single-leg squat. Eccentric hip abductor and lateral rotator torques were measured using an isokinetic dynamometer. The results showed that women had greater contralateral pelvic depression, femur adduction, and knee abduction than men. The eccentric hip abductor and lateral rotator torques were correlated with coronal plane femur and knee movements in the overall sample. When the genders were analyzed separately, it was observed that women with greater eccentric hip abductor torque exhibited less femur adduction and femur medial rotation, and greater knee adduction excursion. No significant relationship was observed between the isokinetic and kinematic variables in the male group. The differences between the genders help to explain the greater rate of knee disorders observed in women. Moreover, the eccentric hip abduction action seemed to be more important in women to control the lower-limb movements.

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Takayuki Hasegawa, Toshiro Otani, Kentaro Takeda, Hideo Matsumoto, Kengo Harato, Yoshiaki Toyama and Takeo Nagura

The purpose of the current study was to longitudinally evaluate how preoperative knee kinematics change after ACL reconstruction. Three-dimensional gait analysis using the point cluster method was undertaken on the same subjects preoperatively and at 3, 6, and 12 months after ACL reconstructive surgery. Thirteen subjects (7 males, 6 females) were examined while performing 2 different activities at self-selected speeds: walking and walk-pivoting (walking, pivoting toward the landed limb side and walking away). The contralateral knees of subjects at 12 months postoperatively were selected as control knees. Flexion range in the stance phase increased with time after surgery, but remained lower than in the contralateral knee, even at 12 months postoperatively (P < .05) during walking and walk-pivoting. The rotation pattern during walking and walk-pivoting showed an offset toward external rotation by 6 months postoperatively compared with control knees, while at 12 months postoperatively the offset had nearly disappeared and the movement pattern resembled that in control knees. These findings suggest that a return to sport participation by 6 months after ACL reconstruction requires careful consideration. Depending on the type of sport, activity restriction even after 12 months may need to be considered to allow complete kinematic restoration.

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Wen-Hao Hsu, Evelyn J. Park, Daniel L. Miranda, Hani M. Sallum, Conor J. Walsh and Eugene C. Goldfield

This study examines how adults apply forces to regulate new walkers’ body sway directions while assisting them in standing and initiating their first steps. Eight healthy, typically developing young children who could stand independently and walk a few steps with an adult’s support participated in this study and were included for data analyses. Adults wore instrumented force gloves and placed their hands on their child’s hips to assist them in standing, then released glove contact with their child to allow their child to initiate walking. Using the glove force profiles, three phases (Stabilization, Relaxation, and Initiation) of adults’ support were determined. Results showed that adults gradually reduced their assistance in both the antero-posterior (AP) and mediolateral (ML) directions, before releasing their hands. They also influenced the directionality of their child’s center of mass (CoM) so that it was in the AP rather than ML direction. Furthermore, the behavior of the child’s CoM in the ML direction during the Initiation Phase was related to the latency with which the child initiated the first step. These findings support the view that adults play a role in modulating the directionality of the child’s body motion by transforming body sway into gait initiation.

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Kai Yan Lui, Patricia Hewston and Nandini Deshpande

During sit-to-stand (STS), the vestibular system is highly stimulated in response to linear acceleration of the head and may play an important role, in addition to vision, for postural control. We examined the effects of aging on visual–vestibular interaction for postural control during STS in 15 young (22.5 ± 1.1 years) and 15 older (73.9 ± 5.3 years) participants. Vestibular information was manipulated using galvanic vestibular stimulation. Vision conditions involved normal (eyes open), suboptimal (blurring goggles), and no (eyes closed) vision. Older participants had significantly greater mediolateral peak-to-peak trunk roll (p = .025) and center of mass displacements (p < .001) than young participants. However, despite having greater mediolateral instability, older participants utilized similar strategies as young participants to overcome sensory perturbations during STS. Overall visual inputs were more dominantly used for mediolateral trunk control during STS than vestibular inputs.

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Tishya A.L. Wren and Paul C. Mitiguy

Clinical gait analysis usually describes joint kinematics using Euler angles, which depend on the sequence of rotation. Studies have shown that pelvic obliquity angles from the traditional tilt-obliquity-rotation (TOR) Euler angle sequence can deviate considerably from clinical expectations and have suggested that a rotation-obliquity-tilt (ROT) Euler angle sequence be used instead. We propose a simple alternate approach in which clinical joint angles are defined and exactly calculated in terms of Euler angles from any rotation sequence. Equations were derived to calculate clinical pelvic elevation, progression, and lean angles from TOR and ROT Euler angles. For the ROT Euler angles, obliquity was exactly the same as the clinical elevation angle, rotation was similar to the clinical progression angle, and tilt was similar to the clinical lean angle. Greater differences were observed for TOR. These results support previous findings that ROT is preferable to TOR for calculating pelvic Euler angles for clinical interpretation. However, we suggest that exact clinical angles can and should be obtained through a few extra calculations as demonstrated in this technical note.

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Matthew D. Portas, Jamie A. Harley, Christopher A. Barnes and Christopher J. Rush

Purpose:

The study aimed to analyze the validity and reliability of commercially available nondifferential Global Positioning System (NdGPS) devices for measures of total distance during linear, multidirectional and soccer-specific motion at 1-Hz and 5-Hz sampling frequencies.

Methods:

Linear (32 trials), multidirectional (192 trials) and soccer-specific courses (40 trials) were created to test the validity (mean ± 90% confidence intervals), reliability (mean ± 90% confidence intervals) and bias (mean ± 90% confidence intervals) of the NdGPS devices against measured distance. Standard error of the estimate established validity, reliability was determined using typical error and percentage bias was established.

Results:

The 1-Hz and 5-Hz data ranged from 1.3% ± 0.76 to 3.1% ± 1.37 for validity and 2.03% ± 1.31 to 5.31% ± 1.2 for reliability for measures of linear and soccer-specific motion. For multidirectional activity, data ranged from 1.8% ± 0.8 to 6.88% ± 2.99 for validity and from 3.08% ± 1.34 to 7.71% ± 1.65 for reliability. The 1-Hz underestimated some complex courses by up to 11%.

Conclusions:

1-Hz and 5-Hz NdGPS could be used to quantify distance in soccer and similar field-based team sports. Both 1-Hz and 5-Hz have a threshold beyond which reliability is compromised. 1-Hz also underestimates distance and is less valid in more complex courses.

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Darren Burgess, Geraldine Naughton and Kevin Norton

Purpose:

The understanding of the gap between Under 18 y (U18) and senior-level competition and the evolution of this gap in Australian Football lack a strong evidence base. Despite the multimillion dollars invested in recruitment, scientific research on successful transition is limited. No studies have compared individual players’ movement rate, game statistics and ball speed in U18 and senior competition of the Australian Football League across time. This project compared differences in player movement and ball speed between matches from senior AFL competitive matches and U18 players in the 2003 and 2009 seasons.

Methods:

TrakPerformance Software and Global Positioning System (GPS) technology were used to analyze the movement of players, ball speed and game statistics. ANOVA compared the two levels of competition over time.

Results:

Observed interactions for distance traveled per minute of play (P = .009), number of sprints per minute of play (P < .001), time spent at sprint speed in the game (P < .001), time on field (P < .001), and ball speed (P < .001) were found. Subsequent analysis identified increases in movement patterns in senior AFL competition in 2009 compared with the same level of competition in 2003 and U18 players in 2003 and 2009.

Conclusions:

Senior AFL players in 2009 were moving further, sprinting relatively more frequently, playing less time and playing at game speeds significantly greater than the same senior competition in 2003 as well as compared with both cohorts of U18 players.

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Brendan R. Scott, Robert G. Lockie, Timothy J. Knight, Andrew C. Clark and Xanne A.K. Janse de Jonge

Purpose:

To compare various measures of training load (TL) derived from physiological (heart rate [HR]), perceptual (rating of perceived exertion [RPE]), and physical (global positioning system [GPS] and accelerometer) data during in-season field-based training for professional soccer.

Methods:

Fifteen professional male soccer players (age 24.9 ± 5.4 y, body mass 77.6 ± 7.5 kg, height 181.1 ± 6.9 cm) were assessed in-season across 97 individual training sessions. Measures of external TL (total distance [TD], the volume of low-speed activity [LSA; <14.4 km/h], high-speed running [HSR; >14.4 km/h], very high-speed running [VHSR; >19.8 km/h], and player load), HR and session-RPE (sRPE) scores were recorded. Internal TL scores (HR-based and sRPE-based) were calculated, and their relationships with measures of external TL were quantified using Pearson product–moment correlations.

Results:

Physical measures of TD, LSA volume, and player load provided large, significant (r = .71−.84; P < .01) correlations with the HR-based and sRPE-based methods. Volume of HSR and VHSR provided moderate to large, significant (r = .40−.67; P < .01) correlations with measures of internal TL.

Conclusions:

While the volume of HSR and VHSR provided significant relationships with internal TL, physical-performance measures of TD, LSA volume, and player load appear to be more acceptable indicators of external TL, due to the greater magnitude of their correlations with measures of internal TL.

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Christoph Schütz, Matthias Weigelt, Dennis Odekerken, Timo Klein-Soetebier and Thomas Schack

Previous studies on sequential effects of human grasping behavior were restricted to binary grasp type selection. We asked whether two established motor control strategies, the end-state comfort effect and the hysteresis effect, would hold for sequential motor tasks with continuous solutions. To this end, participants were tested in a sequential (predictable) and a randomized (nonpredictable) perceptual-motor task, which offered a continuous range of posture solutions for each movement trial. Both the end-state comfort effect and the hysteresis effect were reproduced under predictable, continuous conditions, but only the end-state comfort effect was present under nonpredictable conditions. Experimental results further revealed a work range restriction effect, which was reproduced for the dominant and the nondominant hand.