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Karl M. Newell and Gareth Irwin

A long-held viewpoint in the coordination and control of human movement is that the emerging kinetic/kinematic output within both the upper (i.e., shoulder, elbow, wrist) and lower (i.e., hip, knee, ankle) limb patterns of joint motion follows a proximal–distal sequential order. The proximal

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Ben Serrien, Maggy Goossens, and Jean-Pierre Baeyens

, Della-Grasta, Farrell, & Laurent, 1997 ). Despite this great complexity and variations between different sport motions, typical overhand throwing and striking actions show similar topological proximal-to-distal (P-D) sequencing patterns in muscle activity and kinematics ( Hirashima, Kadota, Sakurai

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Kelly L. Adler, P. Christopher Cook, and Brian D. Giordano

Injury to the rectus femoris (RF) myotendinous complex is the most common location of quadriceps injury, due to combined loads of stretch and eccentric muscular activation. To our knowledge, open proximal RF repair has been reported, but a thorough description of postoperative rehabilitation and functional progression of athletic activity has not been described. This case report outlines the rehabilitation of a 30-year-old female following open proximal RF repair after 15 months of failed conservative treatment. Six months postoperatively she returned to competitive recreational soccer with no complaints.

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Kathryn C. Nesbit, Thubi A. Kolobe, Sandra H. Arnold, Susan B. Sisson, and Michael P. Anderson

Background:

The purpose of this study was to determine how proximal (home) and distal (neighborhood) environmental characteristics interact to influence obesity in early and middle adolescents.

Methods:

This was a descriptive, cross-sectional study using the 2007 National Survey of Children’s Health (NCSH). Participants were 39,542 children ages 11 to 17 years. Logistic regressions were used to examine the relationship between adolescent obesity and environmental factors, the relative strength of these factors, and the influence of age and gender.

Results:

Proximal environmental factors were stronger correlates of adolescent obesity than distal environmental factors. Sedentary behavior related to TV watching time at home was the strongest correlate of adolescent obesity overall (OR 1.13, 95% CI 1.11–1.15). Parks and playgrounds (OR 0.86, 95% CI 0.08–0.92), as well as recreation centers (OR 0.91, 95% CI 0.85–0.97) were significant distal environmental factor correlates. Girls and middle adolescents were at less risk for obesity than boys and early adolescents (OR 0.51, 95% CI 0.68–0.82; OR 0.75, 95% CI 0.68–0.96).

Conclusion:

The results of this study reveal the importance of proximal environmental characteristics on adolescent obesity relative to distal environmental characteristics. Obesity intervention strategies for adolescents should target sedentary behavior and opportunities for physical activity with a focus on early adolescents and boys.

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Thomas G. Ribble, Michael H. Santare, and Freeman Miller

Finite element models of the proximal femur at birth, 2 years of age, and at 8 years of age were constructed to investigate stress patterns under different loading conditions. These loading conditions represent typical activities of a normal developing child and abnormal activity associated with muscle spasticity. The hypothesis is that the shear stresses in the growth plate correlate with the neckshaft angle as associated with valgus and normal development. Loads for the finite element models were derived from a separate muscle model used to calculate the forces across the hip joint for an arbitrary subject and activity. Results show there is an inverse relationship between the relative magnitude of the shear stress in the growth plate and the developing neck-shaft angle. The relatively high shear stresses generated by normal activity in the 2-year-old’s growth plate correlate with the decrease in neck-shaft angle that accompanies normal development. Alternatively, lower shear stresses are generated in the growth plate by loading conditions representing spasticity. These lower magnitude shear stresses correlate with a valgus deformity, which is often observed clinically.

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Timothy C. Sell, Jonathan S. Akins, Alexis R. Opp, and Scott M. Lephart

Proximal anterior tibia shear force is a direct loading mechanism of the anterior cruciate ligament (ACL) and is a contributor to ACL strain during injury. Measurement of this force during competition may provide insight into risk factors for ACL injury. Accelerometers may be capable of measuring tibial acceleration during competition. The purpose of this study was to examine the relationship between acceleration measured by a tibia-mounted accelerometer and proximal anterior tibia shear force as measured through inverse dynamics and peak posterior ground reaction forces during two leg stop-jump tasks. Nineteen healthy male subjects performed stop-jump tasks across increasing jump distances. Correlation coefficients were calculated to determine if a relationship exists between accelerometer data and proximal anterior tibia shear force and peak posterior ground reaction force. An analysis of variance was performed to compare these variables across jump distance. Significant correlations were observed between accelerometer data and peak posterior ground reaction force, but none between accelerometer data and proximal anterior tibia shear force. All variables except peak proximal anterior tibia shear force increased significantly as jump distance increased. Overall, results of this study provide initial, positive support for the use of accelerometers as a useful tool for future injury prevention research.

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Thomas G. Bowman and Riann Palmieri-Smith

Objective:

To present the case of an 18-year-old collegiate decathlete with a Salter-Harris type I epiphyseal plate fracture of the proximal humerus.

Background:

A collegiate decathlete was playing flag football and fell on an outstretched arm. He was taken to the emergency room and diagnosed with a type I epiphyseal plate fracture.

Differential Diagnosis:

AC sprain, dislocation or subluxation, rotator cuff tear, labral tear.

Treatment:

Active and passive range of motion exercises were completed after two days of immobilization. He then started strengthening exercises and returned to competitive activity in 10 weeks.

Uniqueness:

Proximal humeral epiphyseal plate fractures are uncommon injuries, especially in athletes over the age of 15.

Conclusions:

If an accurate diagnosis is made, an appropriate conservative rehabilitation program can be implemented to safely return an athlete to participation without permanent deformity following a type I Salter-Harris fracture.

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Michael P. Reiman, Lori A. Bolgla, and Daniel Lorenz

The purpose of this commentary is to describe the multifactorial relationships between hip-joint strength, range of motion, kinetics/kinematics, and various knee pathologies, specifically as they relate across an individual’s life span. Understanding the interdependence between the hip and knee joints in respect to functional activity is a necessary and relevant aspect for clinicians to investigate to ameliorate various pathological presentations at the knee that might have a proximal relationship.

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Jules Woolf, Rajiv N. Rimal, and Pooja Sripad

Understanding what influences adolescent athletes is important for managers designing anti-doping initiatives. It is commonly assumed that elite athletes who dope influence adolescent athletes to similarly dope. Using the theory of normative social behavior, the effect of norms on adolescent athletes’ intentions to use steroids was examined. The social distance between respondents and the source of normative information was systematically varied to include four separate levels (friends, teammates, college athletes, professional athletes). Data were collected from 404 male adolescent athletes. Participants indicated their intentions to use steroids and their perceptions of descriptive and injunctive norms of referent others. Descriptive and injunctive norms were predictive of intentions to use steroids with the magnitude of explained variance greater with more proximal referents. Adolescent athletes’ intentions to use steroids are influenced by social norms. Moreover, the social distance of referents is consequential. Interventions strategies should incorporate teammates and friends, rather than professional athletes.

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Daniel J. Petit, John D. Willson, and Joaquin A. Barrios

Efforts to compare different surface marker configurations in 3-dimensional motion analysis are warranted as more complex and custom marker sets become more common. At the knee, different markers can been used to represent the proximal shank. Often, two anatomical markers are placed over the femoral condyles, with their midpoint defining both the distal thigh and proximal shank segment ends. However, two additional markers placed over the tibial plateaus have been used to define the proximal shank end. For this experiment, simultaneous data for both proximal shank configurations were independently collected at two separate laboratories by different investigators, with one laboratory capturing a walking population and the other a running population. Common discrete knee joint variables were then compared between marker sets in each population. Using the augmented marker set, peak knee flexion after weight acceptance was less (1.2−1.7°, P < .02) and peak knee adduction was greater (0.7−1.4°, P < .001) in both data sets. Similarly, the calculated peak knee flexion moment was less by 15–20% and internal rotation moment was greater by 11–18% (P < .001). These results suggest that the calculation of knee joint mechanics are influenced by the proximal shank’s segment endpoint definition, independent of dynamic task, investigator, laboratory environment, and population in this study.