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Lisa T. Hoglund, Howard J. Hillstrom, Ann E. Barr-Gillespie, Margery A. Lockard, Mary F. Barbe and Jinsup Song

Increased joint stress and malalignment are etiologic factors in osteoarthritis. Static tibiofemoral frontal plane malalignment is associated with patellofemoral osteoarthritis (PFOA). Patellofemoral joint stress is increased by activities such as sit-to-stand (STS); this stress may be even greater if dynamic frontal plane tibiofemoral malalignment occurs. If hip muscle or quadriceps weakness is present in persons with PFOA, aberrant tibiofemoral frontal plane movement may occur, with increased patellofemoral stress. No studies have investigated frontal plane tibiofemoral and hip kinematics during STS in persons with PFOA or the relationship of hip muscle and quadriceps strength to these motions. Eight PFOA and seven control subjects performed STS from a stool during three-dimensional motion capture. Hip muscle and quadriceps strength were measured as peak isometric force. The PFOA group demonstrated increased peak tibial abduction angles during STS, and decreased hip abductor, hip extensor, and quadriceps peak force versus controls. A moderate inverse relationship between peak tibial abduction angle and peak hip abductor force was present. No difference between groups was found for peak hip adduction angle or peak hip external rotator force. Dynamic tibiofemoral malalignment and proximal lower extremity weakness may cause increased patellofemoral stress and may contribute to PFOA incidence or progression.

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Alexandra Milligan, Chris Mills and Joanna Scurr

More and more studies are emerging reporting breast kinematics. These studies rarely present effect sizes, power, and variance in the data. Important inferences are drawn from these data, including applications to product design, breast pain assessment, sports performance effects, and more. The aim of the study was to explore the within-participant variance in breast kinematic data during a 5 km run. Multiplanar breast kinematics and within-participant variance, defined by the coefficient of variation, for 10 female participants wearing a low and high level breast support were calculated during a 5 km run. Greater within-participant variance was reported in the high level (mean = 15%) breast support compared with the low level (mean = 12%). Within-participant variance in breast kinematics did not change over the 5 km run. Differences in the magnitude of within-participant variance in breast kinematics were reported between directions of breast movement, with greater levels in the anteroposterior direction compared with mediolateral and vertical. It is important for the progression of this research area that the presence and sources of within-participant variance in breast kinematics are quantified and acknowledged, ensuring that the margin for meaningful differences can be reported.

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Gilbert M. Willett, Gregory M. Karst, Ellen M. Canney, Derrick Gallant and Jodene M. Wees

The purpose of this study was to investigate the electromyographic (EMG) activity of selected lower limb muscles during forward- and backward-facing stair-stepping exercises using a hydraulic step ergometer and during step aerobics using a standard 8 in. high step. Surface electrodes recorded EMG data from the vastus lateralis (VL), vastus medialis obliquus (VMO), and biceps femoris (BF) muscles on the right lower limbs of 13 healthy subjects under each of the four exercise conditions. Normalized mean EMG amplitude data were used to test for activity-dependent differences. Results indicated that (a) the VL and VMO were significantly (p < .05) more active during step ergometry than during step aerobics, (b) the BF was significantly (p < .05) more active during step aerobics than during step ergometry, and (c) when forward- versus backward-facing positions were compared, there were no statistically significant differences in mean EMG activity for either of the activities. These findings provide information relevant to the use and progression of stepping exercises commonly used for knee muscle strengthening and knee injury rehabilitation programs.

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Jessica R. Edler, Kenneth E. Games, Lindsey E. Eberman and Leamor Kahanov

The tibial plateau is a critical load-bearing surface in humans. Although tibial plateau fractures represent only 1% of all fractures, proper management by all members of the health care team, including athletic trainers, physicians, and physical therapists, is required for successful patient outcomes. A 14-year-old national-level competitive female diver injured her right knee during the precompetition warm-up period. Upon evaluation by an athletic trainer, the patient was referred for imaging and examination by a physician. She was seen by an orthopedic surgeon for consultation. The patient elected for a surgical repair of the tibial plateau fracture. Following surgery she underwent an 11-week comprehensive therapeutic exercise program with athletic trainers and physical therapists. The patient’s return-to-play progression included dry land activities, platform diving, 1-m springboard diving, and 3-m springboard diving. The patient has successfully returned to competitive diving. Proper identification of tibial fractures can be difficult considering their low occurrence in youth and their similar clinical presentation to more common youth injuries such as anterior cruciate ligament ruptures. Clinicians providing immediate on-site medical care should be thorough in their clinical exam including palpation and axial loading of the joint.

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Vishveshwar R. Mantha, António J. Silva, Daniel A. Marinho and Abel I. Rouboa

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.

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Rachel S. Johnson, Mia K. Provenzano, Larynn M. Shumaker, Tamara C. Valovich McLeod and Cailee E. Welch Bacon

Clinical Scenario:

It is hypothesized that cognitive activity following a concussion may potentially hinder patient recovery. While the recommendation of cognitive rest is often maintained and rationalized, a causal relationship between cognitive activity and symptom duration has yet to be established.

Clinical Question:

Does the implementation of cognitive rest as part of the postconcussion management plan reduce the number of days until the concussed adolescent patient is symptom free compared to a postconcussion management plan that does not incorporate cognitive rest?

Summary of Key Findings:

A thorough literature search returned 7 possible studies; 5 studies met the inclusion criteria and were included. Three studies indicated that increased cognitive activity is associated with longer recovery from a concussion, and, therefore, supported the use of cognitive rest. One study indicated that the recommendation for cognitive rest was not significantly associated with time to concussion symptom resolution. One study indicated that strict rest, defined as 5 days of no school, work, or physical activity; might prolong symptom duration.

Clinical Bottom Line:

There is moderate evidence to support the prescription of moderate cognitive rest for concussed patients. Clinicians who intend on implementing cognitive rest in their concussion protocols should be aware of inconsistencies and be open-minded to alternative treatment progressions while taking into consideration each individual patient and maintaining adequate patient-centered care principles.

Strength of Recommendation:

Grade B evidence exists that prescription of moderate cognitive rest for concussed patients may be beneficial as a supplement to physical rest as treatment for symptom reduction in adolescents.

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Amber Collins, Troy Blackburn, Chris Olcott, Joanne M. Jordan, Bing Yu and Paul Weinhold

Extended use of knee sleeves in populations at risk for knee osteoarthritis progression has shown functional and quality of life benefits; however, additional comprehensive kinematic and kinetic analyses are needed to determine possible physical mechanisms of these benefits which may be due to the sleeve’s ability to enhance knee proprioception. A novel means of extending these enhancements may be through stochastic resonance stimulation. Our goal was to determine whether the use of a knee sleeve alone or combined with stochastic resonance electrical stimulation improves knee mechanics in knee osteoarthritis. Gait kinetics and kinematics were assessed in subjects with medial knee osteoarthritis when presented with four conditions: control1, no electrical stimulation/sleeve, 75% threshold stimulation/sleeve, and control2. An increase in knee flexion angle throughout stance and a decrease in flexion moment occurring immediately after initial contact were seen in the stimulation/sleeve and sleeve alone conditions; however, these treatment conditions did not affect the knee adduction angle and internal knee abduction moment during weight acceptance. No differences were found between the sleeve alone and the stochastic resonance with sleeve conditions. A knee sleeve can improve sagittal-plane knee kinematics and kinetics, although adding the current configuration of stochastic resonance did not enhance these effects.

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Hayri Baran Yosmaoglu, Gül Baltaci, Defne Kaya and Hamza Ozer

Context:

The development pattern of motor coordination, strength, and functional ability during recovery from anterior cruciate ligament (ACL) reconstruction.

Objective:

To investigate the relationship between motor coordination, functional ability, and strength after ACL reconstruction.

Design:

Prospective clinical follow-up study.

Setting:

Sports-injury research laboratory.

Participants:

20 subjects who underwent ACL reconstruction.

Interventions:

Real-time eccentric and concentric motor coordination were tested by a multijoint lower limb tracking-trajectory test, quadriceps and hamstring isokinetic strength were assessed by isokinetic dynamometer, and functional performance was tested with a single-leg-hop test 6 and 12 mo after ACL reconstruction.

Main Outcome Measures:

Percentage deficits of the involved lower extremity for target-tracking ability, peak torque, total work parameters of isokinetic strength, and single-leg-hop distance.

Results:

Deficits in hamstring–quadriceps isokinetic muscle strength and single-leg-hop distance significantly decreased from the 6th to the 12th mo after surgery (P < .05). There were no significant differences in muscle concentric and eccentric motor-coordination deficits of the involved side (P > .05).

Conclusions:

Although muscle strength and functional performance clearly increased from the 6th to the 12th mo after surgery, coordination characteristics of involved side remained low. This pattern demonstrated that motor-coordination progression was not affected by strength development. Patients continued to have significant motor-coordination deficits even 12 mo postsurgery. Therefore, the authors recommend that neuromuscular-coordination exercises be included in long-term rehabilitation programs to improve motor coordination.

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Li Jin, Peter G. Adamczyk, Michelle Roland and Michael E. Hahn

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater knee loading in the frontal plane has been related to severity and rate of progression in knee osteoarthritis. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. However, little is known about specific effects that prosthetic foot damping may have on uninvolved limb loading. We hypothesized that uninvolved limb peak knee internal abduction moment (IAM) and loading rates would be greater when using a high-damping foot compared with a low-damping foot, across walking speeds. Eight healthy, young subjects walked in a prosthesis simulator boot using the experimental feet. Greater uninvolved limb first peak IAM (+16% in fast speed, P = .002; +11% in slow speed, P = .001) and loading rates (+11% in fast speed, P = .003) were observed when using the high-damping foot compared with low-damping foot. Within each foot, uninvolved limb first peak IAM and loading rates had a trend to increase with increased walking speed. These findings suggest that damping properties of prosthetic feet are related to uninvolved limb peak knee IAM and loading rates.

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Paavo V. Komi

To understand cross-country (X-C) siding it is important to record and identity forces of skis and poles separately and together. They both contribute to the forward progression, but their functional significance may be more complex than that of the ground reaction forces in running and walking. This report presents two methods to record forces on skis and poles during normal X-C skiing. A long force-platform system with four rows of 6-m long plates is placed under the snow track for recording of Fz and Fy forces of each ski and pole separately. This system is suitable especially for the study of diagonal technique under more strict experimental conditions. The second system consists of small lightweight Fz and Fy component force plates which are installed under the boot and binding. These plates can be easily changed from one ski to another, and telemetric recording allows free skiing over long distances and with different skiing techniques, including skating. The presentation emphasizes the integrated use of either system together with simultaneous cinematographic and electromyographic recordings.