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Alex V. Rowlands, Tatiana Plekhanova, Tom Yates, Evgeny M. Mirkes, Melanie Davies, Kamlesh Khunti and Charlotte L. Edwardson

, Keane, Harrington, & Fitzgerald, 2017 ); and British Whitehall II Study ( Menai et al., 2017 ), ≅3750 participants. Of these, the Axivity was used in UK Biobank and the Breakthrough Generation Study, the ActiGraph in NHANES, and the GENEActiv in the remaining surveys. All surveys deployed monitors on

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Gianluca Gatti

This article presents the validation of a technique to assess the appropriateness of a 2 degree-of-freedom model for the human knee, and, in which case, the dominant axes of flexion/extension and internal/external longitudinal rotation are estimated. The technique relies on the use of an instrumented spatial linkage for the accurate detection of passive knee kinematics, and it is based on the assumption that points on the longitudinal rotation axis describe nearly circular and planar trajectories, whereas the flexion/extension axis is perpendicular to those trajectories through their centers of rotation. By manually enforcing a tibia rotation while bending the knee in flexion, a standard optimization algorithm is used to estimate the approximate axis of longitudinal rotation, and the axis of flexion is estimated consequently. The proposed technique is validated through simulated data and experimentally applied on a 2 degree-of-freedom mechanical joint. A procedure is proposed to verify the fixed axes assumption for the knee model. The suggested methodology could be possibly valuable in understanding knee kinematics, and in particular for the design and implant of customized hinged external fixators, which have shown to be effective in knee dislocation treatment and rehabilitation.

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Aaron Chin, David Lloyd, Jacqueline Alderson, Bruce Elliott and Peter Mills

The predominance of upper-limb elbow models have been based on earlier lower-limb motion analysis models. We developed and validated a functionally based 2 degree-of-freedom upper-limb model to measure rotations of the forearm using a marker-based approach. Data were collected from humans and a mechanical arm with known axes and ranges of angular motion in 3 planes. This upper-limb model was compared with an anatomically based model following the proposed ISB standardization. Location of the axes of rotation relative to each other was determined in vivo. Data indicated that the functional model was not influenced by cross-talk from adduction-abduction, accurately measuring flexion-extension and pronation-supination. The functional flexion-extension axis in vivo is angled at 6.6° to the anatomical line defined from the humeral medial to lateral epicondyles. The pronation-supination axis intersected the anatomically defined flexion-extension axis at 88.1°. Influence of cross-talk on flexion-extension kinematics in the anatomical model was indicated by strong correlation between flexion-extension and adduction-abduction angles for tasks performed by the subjects. The proposed functional model eliminated cross-talk by sharing a common flexion axis between the humerus and forearm. In doing so, errors due to misalignment of axes are minimized providing greater accuracy in kinematic data.

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Adrienne E. Hunt and Richard M. Smith

Three-dimensional ankle joint moments were calculated in two separate coordinate systems, from 18 healthy men during the stance phase of walking, and were then compared. The objective was to determine the extent of differences in the calculated moments between these two commonly used systems and their impact on interpretation. Video motion data were obtained using skin surface markers, and ground reaction force data were recorded from a force platform. Moments acting on the foot were calculated about three orthogonal axes, in a global coordinate system (GCS) and also in a segmental coordinate system (SCS). No differences were found for the sagittal moments. However, compared to the SCS, the GCS significantly (p < .001) overestimated the predominant invertor moment at midstance and until after heel rise. It also significantly (p < .05) underestimated the late stance evertor moment. This frontal plane discrepancy was attributed to sensitivity of the GCS to the degree of abduction of the foot. For the transverse plane, the abductor moment peaked earlier (p < .01) and was relatively smaller (p < .01) in the GCS. Variability in the transverse plane was greater for the SCS, and attributed to its sensitivity to the degree of rearfoot inversion. We conclude that the two coordinate systems result in different calculations of nonsagittal moments at the ankle joint during walking. We propose that the body-based SCS provides a more meaningful interpretation of function than the GCS and would be the preferred method in clinical research, for example where there is marked abduction of the foot.

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Michael J. Axe and Jeff Konin

The decision of how to progress a baseball player through a throwing program following an injury has been a difficult one for the sports medicine population to address. Numerous programs have been suggested to allow a player a gradual return to competitive throwing. These programs are primarily based on previous experience of the clinician designing the program, simply because this may be the only objective material that can be used to determine parameters of a program of such diverse individualism. This paper identifies those components that play a critical role in the designing of any interval throwing program and outlines a program based on position and distance specific phases.

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Jeff Konin, Michael J. Axe and Ron Courson

The implementation of interval throwing programs during rehabilitation has been suggested in the literature to allow for a quicker and safer return of the throwing athlete to competition. Many programs have clearly focused on baseball players. This program is specifically designed for the football quarterback. The program encompasses a sound flexibility and strength training regime and provides for a supervised step-by-step progression of throwing. Although the authors have found success with early results, practitioners should apply this program with caution, as it may need to be modified for each athlete. The purpose of this paper is to establish a foundation for future work in the area of the throwing shoulder for the football quarterback.

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Michael J. Axe, Thomas C. Windley and Lynn Snyder-Mackler

Objective:

To design interval throwing programs for baseball players other than pitchers from 13 years of age to the college level.

Design:

The authors recorded throws to base, distance of throws, and perceived effort of throws at 4 levels of play. For catchers they also recorded number of throws to the pitcher, number of sprints to first or third base, and time in the squat stance. From these data they designed throwing programs specific to outfielders, infielders, and catchers.

Results:

No significant difference was found between the number of throws and distance of throws for infielders and catchers across all age groups. The mean distance of throws differed significantly between 13-year-olds and all other levels of play.

Conclusion:

The authors devised 1 program for infielders and catchers of all age groups, 1 program for 13-year-old outfielders, and 1 for all other levels.

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Michael J. Axe, Katherine Linsay and Lynn Snyder-Mackler

The purpose of this study was to determine whether there was a relationship between knee hyperextension and intra-articular pathology in 100 consecutive patients whose sole ligament injury was an arthroscopically confirmed anterior cruciate ligament (ACL) rupture. Hyperextension of both knees was measured using a supine heel-height measurement of high reliability. There was more articular damage to the total joint, lateral joint, and lateral meniscus in patients who hyperextended than in those who did not. There was more articular damage to the total joint and medial joint in patients who were chronically ACL deficient than in those who were acutely or subacutely ACL deficient. The results demonstrate that individuals with ACL injuries whose knees hyperextend 3 cm or more sustain significantly more joint damage at the time of injury than in those whose knees hyperextend less than 3 cm. This study further defines the role of knee hyperextension in ACL injuries and offers a useful and reliable means of measuring knee hyperextension.

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Michael J. Axe, Kirk H. Swigart and Lynn Snyder-Mackler