instructions, such as those utilized by exercise professionals, influence patellofemoral joint loading during bodyweight squatting. Verbal instructions regarding exercise technique can be slightly modified to promote either an internal focus of attention (FoAin) or an external focus of attention (FoAex). 17
Thomas G. Almonroeder, Emily Watkins, and Tricia Widenhoefer
Abbigail Ristow, Matthew Besch, Drew Rutherford, and Thomas W. Kernozek
(PFJCA), 4 and abnormal joint loading. 3 PFJS is calculated from PFJRF and PFJCA. 6 Commonly, PFJS is higher in females due to less PFJCA when compared with males. 7 Many variables contribute to increased PFJS, including trauma, overuse, lower-extremity malalignment, muscle imbalance, muscle weakness
Kyoungyoun Park-Braswell, Sandra J. Shultz, and Randy J. Schmitz
demonstrated to result in altered brain activation patterns during lower leg movement tasks. 6 This may indicate possible neuroplasticity in response to sensory alteration from the joint. It is understood that mechanoreceptors in the ACL respond to anterior knee joint loading. 4 Neuroimaging techniques such
Joseph Hannon, J. Craig Garrison, Sharon Wang-Price, Shiho Goto, Angellyn Grondin, James Bothwell, and Curtis Bush
Joint loading following anterior cruciate ligament reconstruction (ACL-R) continues to be a topic of interest among researchers, because altered joint loading can contribute to compensatory movements, commonly seen in this patient population. Joint loading has been examined using a variety of
Rebecca L. Lambach, Jay W. Young, David C. Flanigan, Robert A. Siston, and Ajit M.W. Chaudhari
Linemen are at high risk for knee cartilage injuries and osteoarthritis. High-intensity movements from squatting positions (eg, 3-point stance) may produce high joint loads, increasing the risk for cartilage damage. We hypothesized that knee moments and joint reaction forces during lineman-specific activities would be greater than during walking or jogging. Data were collected using standard motion analysis techniques. Fifteen NCAA linemen (mean ± SD: height = 1.86 ± 0.07 m, mass = 121.45 ± 12.78 kg) walked, jogged, and performed 3 unloaded lineman-specific blocking movements from a 3-point stance. External 3-dimensional knee moments and joint reaction forces were calculated using inverse dynamics equations. MANOVA with subsequent univariate ANOVA and post hoc Tukey comparisons were used to determine differences in peak kinetic variables and the flexion angles at which they occurred. All peak moments and joint reaction forces were significantly higher during jogging than during all blocking drills (all P < .001). Peak moments occurred at average knee flexion angles > 70° during blocking versus < 44° in walking or jogging. The magnitude of moments and joint reaction forces when initiating movement from a 3-point stance do not appear to increase risk for cartilage damage, but the high flexion angles at which they occur may increase risk on the posterior femoral condyles.
Miriam Klous, Erich Müller, and Hermann Schwameder
Limited data exists on knee biomechanics in alpine ski turns despite the high rate of injuries associated with this maneuver. The purpose of the current study was to compare knee joint loading between a carved and a skidded ski turn and between the inner and outer leg. Kinetic data were collected using Kistler mobile force plates. Kinematic data were collected with five synchronized, panning, tilting, and zooming cameras. Inertial properties of the segments were calculated using an extended version of the Yeadon model. Knee joint forces and moments were calculated using inverse dynamics analysis. The obtained results indicate that knee joint loading in carving is not consistently greater than knee joint loading in skidding. In addition, knee joint loading at the outer leg is not always greater than at the inner leg. Differentiation is required between forces and moments, the direction of the forces and moments, and the phase of the turn that is considered. Even though the authors believe that the analyzed turns are representative, results have to be interpreted with caution due to the small sample size.
A two-dimensional model has been developed to predict and explain the effects of the variation of muscle moment arms during dynamic exercises involving heavy external loads. The analytical dependence of the muscle moment arm on the joint angle and on the origin and insertion position was derived for an ideal uniaxial hinge joint, modeling the muscle as a cable following an idealized minimum distance path from the origin to insertion that wraps around the bony geometry. Analytical expressions for the ratios of muscular force and the joint restraining reaction components to the external load weight were deduced, for isokinetic and static exercises, as a function of joint angle, joint angular velocity, and the other geometric parameters defining the model. Therefore, external load weight, joint angular velocity, and constraints to joint range of motion may be adjusted reciprocally in order to control in advance the peak value of the components of the joint load during isokinetic exercises. A dynamic formulation of forearm flexion/extension was solved numerically under the condition of constant biceps force in order to highlight the key role played by the variation in muscle moment arm in preventing injury during lifting of external loads against gravity. For example, our analysis indicates that the mean and peak resultant joint loads decrease by 5% and 14%, respectively, as a result of the change in muscle moment arm that occurs over the range of motion.
Norihisa Fujii and Mont Hubbard
A simulation and optimization procedure was constructed to investigate the relationships between optimal movement and muscular strength for baseball pitching. Four segments (torso, upper arms, lower arms, hands) and six torque generators (shoulders, elbows, wrists) are modeled. The torque generators have torque-angle and torque-angular velocity characteristics of Hill-type muscle function. The optimization objective function includes release velocity and negative terms penalizing joint loading and inaccuracy. The weighting coefficient for joint loads has a strong influence on the results. As this coefficient increases, the motion becomes more similar to actual measured pitches. Combining active state patterns optimized for different weighting coefficients gives larger joint loads in the simulated motion. This supports the hypothesis that well-coordinated active states are important for controlling the relationships of the different torque generators in order to create a reasonable and effective pitching motion. The model proposed here is superior to previous simulations for throwing, from the viewpoint of modeling with characteristics of Hill-type muscle function, and can be used to explore realistic baseball pitching.
Guillaume Mornieux, Elmar Weltin, Monika Pauls, Franz Rott, and Albert Gollhofer
with the body weight shifted over the injured leg. 2 Trunk positioning during lateral movements is of interest as it would influence the location of the body weight, and potential knee joint loads. 3 , 4 Hewett and Myer 3 proposed a knee injury model that accounted for both the trunk and hip joints
Oladipo O. Eddo, Bryndan W. Lindsey, Shane V. Caswell, Matt Prebble, and Nelson Cortes
% and 60% in the internal first peak KEM was observed in the nonmodified limb during the small and large medial knee thrust modifications, respectively (Table 2 ). Increased peak KEM is related to increased quadriceps activity leading to increased knee joint loads. 19 The observed concurrent increase