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Mechanisms of Achilles Tendon Rupture in National Basketball Association Players

Adam J. Petway, Matthew J. Jordan, Scott Epsley, and Philip Anloague

A systematic search was performed of online databases for any Achilles tendon (AT) injuries occurring within the National Basketball Association (NBA). Video was obtained of injuries occurring during competition and downloaded for analysis in Dartfish. NBA athletes (n = 27) were identified with AT rupture over a 30-year period (1991–2021). Of the 27 NBA athletes found to have AT ruptures (mean age: 29.3 [3.3] y; average time in the NBA: 8.5 [3.8] y), 15 in-game videos were obtained for analysis. Noncontact rupture was presumed to have occurred in 12/13 cases. Eight of the 13 athletes had possession of the ball during time of injury. The ankle joint of the injured limb for all 13 athletes was in a dorsiflexed position during the time of injury (47.9° [6.5°]). All 13 athletes performed a false-step mechanism at time of injury where they initiated the movement by taking a rearward step posterior to their center of mass with the injured limb before translating forward. NBA basketball players that suffered AT ruptures appeared to present with a distinct sequence of events, including initiating a false step with ankle dorsiflexion of the injured limb at the time of injury.

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Erratum. Shoulder Kinesio Taping Does Not Change Biomechanical Deficits Associated With Scapular Dyskinesis

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Can Increased Locomotor Task Difficulty Differentiate Knee Muscle Forces After Anterior Cruciate Ligament Reconstruction?

Megan J. Schroeder, Samuel A. Acuña, Chandramouli Krishnan, and Yasin Y. Dhaher

Changes in knee mechanics following anterior cruciate ligament (ACL) reconstruction are known to be magnified during more difficult locomotor tasks, such as when descending stairs. However, it is unclear if increased task difficulty could distinguish differences in forces generated by the muscles surrounding the knee. This study examined how knee muscle forces differ between individuals with ACL reconstruction with different graft types (hamstring tendon and patellar tendon autograft) and “healthy” controls when performing tasks with increasing difficulty. Dynamic simulations were used to identify knee muscle forces in 15 participants when walking overground and descending stairs. The analysis was restricted to the stance phase (foot contact through toe-off), yielding 162 separate simulations of locomotion in increasing difficulty: overground walking, step-to-floor stair descent, and step-to-step stair descent. Results indicated that knee muscle forces were significantly reduced after ACL reconstruction, and stair descent tasks better discriminated changes in the quadriceps and gastrocnemii muscle forces in the reconstructed knees. Changes in quadriceps forces after a patellar tendon graft and changes in gastrocnemii forces after a hamstring tendon graft were only revealed during stair descent. These results emphasize the importance of incorporating sufficiently difficult tasks to detect residual deficits in muscle forces after ACL reconstruction.

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Erratum: Kawakami et al (2019)

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The Effects of Wobbling Mass Components on Joint Dynamics During Running

Samuel E. Masters and John H. Challis

Soft tissue moves relative to the underlying bone during locomotion. Research has shown that soft tissue motion has an effect on aspects of the dynamics of running; however, little is known about the effects of soft tissue motion on the joint kinetics. In the present study, for a single subject, soft tissue motion was modeled using wobbling components in an inverse dynamics analysis to access the effects of the soft tissue on joint kinetics at the knee and hip. The added wobbling components had little effect on the knee joint kinetics, but large effects on the hip joint kinetics. In particular, the hip joint power and net negative and net positive mechanical work at the hip was greatly underestimated when calculated with the model without wobbling components compared with that of the model with wobbling components. For example, for low-frequency wobbling conditions, the magnitude of the peak hip joint moments were 50% greater when computed accounting the wobbling masses compared with a rigid body model, while for high-frequency wobbling conditions, the peaks were within 15%. The present study suggests that soft tissue motion should not be ignored during inverse dynamics analyses of running.

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Development and Assessment of a Method to Estimate the Value of a Maximum Voluntary Isometric Contraction Electromyogram from Submaximal Electromyographic Data

Hamid Norasi, Jordyn Koenig, and Gary A. Mirka

The electromyographic (EMG) normalization (often to maximum voluntary isometric contraction [MVIC]) is used to control for interparticipant and day-to-day variations. Repeated MVIC exertions may be inadvisable from participants’ safety perspective. This study developed a technique to predict the MVIC EMG from submaximal isometric voluntary contraction EMG. On day 1, 10 participants executed moment exertions of 100%, 60%, 40%, and 20% of the maximum (biceps brachii, rectus femoris, neck flexors, and neck extensors) as the EMG data were collected. On day 2, the participants replicated the joint moment values from day 1 (60%, 40%, and 20%) and also performed MVIC exertions. Using the ratios between the MVIC EMGs and submaximal isometric voluntary contraction EMG data values established on day 1, and the day 2 submaximal isometric voluntary contraction EMG data values, the day 2 MVIC EMGs were predicted. The average absolute percentage error between the predicted and actual MVIC EMG values for day 2 were calculated: biceps brachii, 45%; rectus femoris, 27%; right and left neck flexors, 27% and 33%, respectively; and right and left neck extensors, both 29%. There will be a trade-off between the required accuracy of the MVIC EMG and the risk of injury due to exerting actual MVIC. Thus, using the developed predictive technique may depend on the study circumstances.

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A Note From Katherine Boyer, the New Journal of Applied Biomechanics Editor-in-Chief

Katherine A. Boyer

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Dr. Richard C. Nelson: A Facilitator and Door Opener

Benno M. Nigg

Dr. Richard Nelson contributed to the development of sport biomechanics by being an international facilitator. Together with Dr. Jürg Wartenweiler, he contributed the necessary support and input that allowed the field of Movement and Sports Biomechanics to develop and flourish.

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Dr. Richard C. Nelson: A Water Tower Remembrance

Robert Shapiro

The author recalls his initial introduction to the field of biomechanics in the Penn State Biomechanics Laboratory, known as the Water Tower, and its positive and profound effect on his lifetime career. Under the directorship of Dr. Richard Nelson, Penn State’s biomechanics program provided the author with a variety of both professional and personal learning opportunities. The author credits these experiences as having a direct relationship to his successful development as teacher, mentor, and researcher.

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Dr. Richard C. Nelson: An Important Multigenerational Father of Biomechanics

Robert W. Norman, Stuart M. McGill, and James R. Potvin

Dr. Richard Nelson is internationally acknowledged in many countries as an extremely important leader in the emergence of biomechanics of human movement as a respected scientific discipline. As his PhD graduates, and, subsequently, their graduates, have become faculty members at many universities, Dr. Nelson’s influence has grown for more than 50 years via several generations of his biomechanics “children.” It was probably never known to him that he also had significant influence on all laboratory-based subdisciplines of the undergraduate and graduate education and faculty research programs of the then new (1967) Department of Kinesiology at the University of Waterloo, Canada. The teaching and research programs included not only biomechanics but also exercise and work physiology, anatomy, biochemistry, and neurophysiology of human movement.