Changes in inter-joint relationships of muscle moments and powers accompanying the acquisition of a multi-articular kicking task

Avulsion Injuries and Ruptures of the Proximal Rectus Femoris in Skeletally Mature, High-Level Athletes: A Critical Analysis Review

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Injuries to the proximal rectus femoris remain rare, occurring primarily in soccer and American football athletes during kicking and sprinting because of its unique biarthrodial nature.

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The appropriate diagnosis is dependent on careful physical examination and imaging interpretation.

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While no universal treatment algorithm has been adopted for high-level athletes, recent investigations support operative repair using suture anchors to restore strength and function in order to allow an effective return to competition while minimizing the risk of injury recurrence.

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Complications following surgical management include injury to the lateral femoral cutaneous nerve and hematoma formation, and there are reports of residual pain and weakness with chronic injuries that fail the initial nonoperative treatment.

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Current investigations examining outcomes following treatment remain limited, warranting additional studies that examine patient-reported results, return-to-play rates, and the role of orthobiologics and accelerated rehabilitation protocols following injury to further improve athlete health and safety.

Influence of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres

Limb dominance theory suggests that females tend to be more one-leg dominant and exhibit greater kinematic and kinetic leg asymmetries than their male counterparts, contributing to the increased risk of anterior cruciate ligament injury among female athletes. Thus, the purpose of this study was to examine the influences of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres. Twenty-one women and 21 men completed land-and-cut manoeuvres on their dominant limb as well as their nondominant limb. Three-dimensional kinematics and kinetics were calculated bilaterally for the entire stance phase of the manoeuvre. Women performed land-and-cut manoeuvres with altered hip motions and loads as well as greater knee abduction at touchdown compared to men. Dominant limb land-and-cut manoeuvres where characterised by decreased hip flexion at touchdown as well as decreased hip flexion and adduction range of motion compared to nondominant land-and-cuts regardless of sex. The observed sex differences are consistent with previous research regarding mechanisms underlying the sex disparity in anterior cruciate ligament injury rates. However, observed differences regarding limb dominances appear somewhat arbitrary and did not suggest that the dominant or nondominant limb would be at increased risk of anterior cruciate ligament injury.

Learning a multi-joint throwing task: a morphometric analysis of skill development

Changes in movement organization were examined during the learning of a multi-joint throwing task. Six participants threw a modified frisbee into the target area over an extended practice period (total of 1,300 trials). Throwing accuracy scores were recorded while 3-D arm motion was collected. Intrinsic shape and variability of end-point path and joint coordination pattern were assessed quantitatively by using generalized procrustes analysis (GPA) to remove extrinsic variability in location, orientation and size of movement configurations. Results indicated that throwing accuracy followed the power law of practice and had an inverse relationship with the actual variability of end-point path. GPA indicated that the intrinsic pattern of end-point path stabilized early during learning while the intrinsic pattern of joint coordination remained variable throughout practice. These findings support the proposal that skill acquisition is composed of two learning processes that occur at different rates. Topology (intrinsic pattern of end-point path) is acquired early during practice, while dynamic control (represented by joint coordination) occurs at a much slower rate.

Mechanical power flow changes during multijoint movement acquisition

We investigated the differences in mechanical power flow in early and late practice stages during a cyclic movement consisting of upper arm circumduction to clarify the change in mechanical energy use with skill acquisition. Seven participants practiced the task every other day until their joint angular movements conformed to those of an expert. During the practice sessions, participants' motions were digitally recorded once a week using four high-speed infrared cameras, and the joint kinematics and joint powers of the right arm were calculated. With practice, the inflow power derived from the net joint force increased at the hand, forearm, and upper arm segments by 143.1 +/- 17.2%, 57.1 +/- 7.3%, and 198.1 +/- 35.4%, respectively. In contrast, the power caused by the muscle joint moments was not significantly increased. These results suggested that participants acquired a motor pattern promoting transfer of the joint reaction forces. Results may provide some support for Bernstein's (1967) ideas that skill acquisition involves improving movement efficiency by greater use of nonmuscular forces.

The influence of experience on knee mechanics during side-step cutting in females

BACKGROUND

It is thought that female athletes with limited experience in a sport perform athletic maneuvers differently than their more experienced counterparts, and that they do so in a manner that places them at greater risk for injury. The purpose of this study was to evaluate the influence of athletic experience on knee mechanics during the execution of a side-step cutting maneuver in young female athletes.

METHODS

Three-dimensional kinematics, ground reaction forces and electromyographic activity (surface electrodes) were recorded during the early deceleration phase of side-step cutting in 30 high school females (15 experienced, 15 novice). Group differences in knee joint kinematics, peak moments, net joint moment impulse and average muscle activation were evaluated.

FINDINGS

No significant group differences were found in knee kinematics. When compared to experienced females, novice females demonstrated significantly smaller flexor, adductor, and internal rotator peak moments and smaller net joint moment impulse in all three planes at the knee. No group differences were found for average EMG; however, novice athletes had significantly greater co-contraction at the knee.

INTERPRETATION

The finding of smaller knee moments and greater muscle co-contraction in the novice group suggests that these athletes may adopt a protective strategy in response to a relatively unfamiliar task. In addition, these results suggest that increased moments at the knee emerge with experience, indicating that more skilled athletes may be at greater risk for anterior cruciate ligament (ACL) injury.

Practice changes the usage of moment components in executing a multijoint task

We examined changes in the usage of muscular and motion-dependent moments during the long-term practice of a complex, multijoint movement. Seven participants practiced a cyclic movement of the upper limbs until their joint angular movements conformed to those of an expert. The motions of the participants were digitally recorded using four high-speed infrared cameras, and the joint kinematics and kinetics of the right arm were calculated. Practice brought about changes in the patterns of the net joint moment and in the contributions of the muscular and motion-dependent moments to the net moments. Practice also brought about a growing opposition between the directions of the two moments. These changes seemed to be important for improving the dynamic equilibrium of the movements.

Prediction of Individual Muscle Forces Using Lagrange Multipliers Method - A Model of the Upper Human Limb in the Sagittal Plane: II. Numerical Experiments and Sensitivity Analysis

Using the method of Lagrange multipliers an analytical solution of the optimization problem formulated for a two-dimensional, 3DOF model of the human upper limb has been described in Part I of this investigation. The objective criterion used is the following: [formula: see text], where F(i) -s are the muscle forces modelled and c(i) -s are unknown weight factors. This study is devoted to the numerical experiments performed in order to investigate which sets of the weight factors may predict physiologically reasonable muscle forces and joint reactions. A sensitivity analysis is also presented. The influence of: the gravity forces, different external loads applied to the hand, changes of the weight factors and of joint angle on the optimal solution is studied. A general conclusion may be drawn: using the above mentioned objective criterion, practically all motor tasks performed by the human upper limb may be described if the c(i) -s are properly chosen. These weight factors generally depend on the joint moments and must be different (their magnitudes as well as their signs) for agonistic muscles and for their antagonists.

Stereotypic muscle-torque patterns are systematically adopted during acquisition of a multi-articular kicking task

Motor-control mechanisms used to learn multi-joint (kinematically indeterminate) movements, which involve the control of intersegmental dynamics, are poorly understood, because the few kinetic studies which examined them studied only a few trials performed early and late in learning. Therefore, we examined changes in movement kinematics and kinetics accompanying multi-joint movement acquisition to address the following questions: Once subjects can produce accurate movements, do motor patterns (i.e. net muscle torques) change with further learning? Are motor patterns learned using a systematic strategy? Following learning, are the same motor patterns consistently used for movement production? Subjects performed 16 blocks of 16 trials of a discrete weighted (mass = 1.674 kg) kicking movement, involving hip, knee, and ankle motion. They attempted to perform 400 ms spatially accurate movements. Kinematics were recorded for the hip, knee, ankle, and toe of the kicking leg, and inverse dynamics were used to obtain net-muscle-torque profiles. Subjects did not adopt the motor patterns initially used to produce accurate movements. With further learning, net muscle torques became less variable both within and between blocks; inter-joint dependency of muscle torques increased, as evidenced by decreased variability in the pair of muscle torques which directly affect a segment's motion (i.e. hip-knee and knee ankle muscle torques); and inter-joint relationships of muscle torques became more phase-locked, with hip and knee torques being produced simultaneously, as were knee and ankle torques. As there was a progression across blocks until the preferred motor patterns were adopted, the learned stereotypic motor patterns were systematically selected.

Intralimb dynamics simplify reactive control strategies during locomotion

The utilization of passive dynamics to control the swing trajectory is one mechanism which serves to minimize energy costs during locomotion, in addition to reducing the complexity of the neural control. In a reactive situation (e.g. trip or slip during walking), the energy cost may not be a major determinant of the locomotor activity as there is a need for quick corrective action under the threat of a fall. Therefore, we addressed the following question: does the nervous system utilize passive dynamics during the reactive control of locomotion? An unexpected mechanical perturbation was applied to the foot during early and late swing during walking. Video data were input into an inverse dynamics routine to obtain the joint moment and mechanical power profiles and to partition the joint moments into active and passive components. The nervous system still utilized the passive dynamics of the effector system; active control of a single joint, the knee joint, passively facilitated the flexor action at the proximal hip and distal ankle joint following the early swing perturbation. The minimization of the mechanical energy cost was not a major determinant for this task since the total mechanical work during the perturbed steps was greater than during normal steps. A neuromuscular constraint was observed following the late swing perturbation; the active control of the hip and knee joints were increased but the magnitude of the hip extensor/knee flexor moment was invariant and equal to 1.6. The intralimb dynamics identified during these responses may serve to simplify the complexity of the active control of the nervous system.

Quantification of the uncertainties in resultant joint moments computed in a dynamic activity

Resultant joint moments are an important variable with which to examine human movement, but the uncertainty with which resultant joint moments are calculated is often ignored. This paper presents a procedure for examining the uncertainty with which resultant joint moments are calculated. The uncertainty was calculated by changing the parameters and variables required to compute the resultant joint moments, by amounts relating to their estimated uncertainties, and then quantifying the resulting change in the resultant joint moments. The procedure was applied to the elbow joint during loaded elbow flexion executed at maximum volitional speed. For this activity, the estimated moments were most sensitive to uncertainties in the derivatives of the position data. A number of other sources of error and uncertainty were identified which warrant further investigation. The protocols outlined in this study are applicable to other activities.