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Bradley Smith, Tina Claiborne and Victor Liberi

The purpose of this study was to determine the effects of ankle bracing on vertical jump performance and lower extremity kinematics and electromyography (EMG) activity. Twenty healthy college athletes participated in two sessions, separated by a minimum of 24 hr. They performed five jumps with no brace on the first day, and five jumps with both ankles braced on the second day. An average of the three highest jumps each day was used for analysis. Braced vertical jump performance significantly decreased (p = .002) as compared with the unbraced condition. In addition, hip flexion (p = .043) and ankle plantar flexion (p = .001) angles were significantly smaller during the braced vertical jump. There was also a significant reduction in soleus muscle EMG (p = .002) during the braced condition.

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Dorsey S. Williams III, Irene S. McClay and Kurt T. Manal

Runners are sometimes advised to alter their strike pattern as a means of increasing performance or in response to injury. The purpose of this study was to compare lower extremity mechanics of rearfoot strikers (RFS), who were instructed to run with a forefoot strike pattern (CFFS) to those of a preferred forefoot striker (FFS). Three-dimensional mechanics of 9 FFS and 9 CFFS were evaluated. Peak values for most kinematic and kinetic variables and all patterns of movement were not found to be statistically different between CFFS and FFS. Only peak vertical ground reaction force and peak ankle plantarflexion moment were found to be significantly lower (p ≤ .05) in the CFFS group. This suggests that RFS are able to assume a FFS pattern with very little practice that is very similar to that of a preferred FFS. The impact of changing one's strike pattern on injury risk and running performance needs further study.

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Jaimie A. Roper, Ryan T. Roemmich, Mark D. Tillman, Matthew J. Terza and Chris J. Hass

stabilize the pelvis as the swing leg progresses forward. 3 , 4 Further, studies have demonstrated that certain lower extremity frontal plane mechanics (ie, impulse of the knee abduction moment and medio-lateral ground reaction forces) change with gait speed. 5 , 6 Interventions that manipulate gait speed

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Neal R. Glaviano and Susan Saliba

identified in individuals with PFP. These impairments can be divided into nonmodifiable (anatomical) and modifiable factors (decreased flexibility, altered kinematics, and lower-extremity weakness). 6 Muscle weakness is a key modifiable deficit that has been identified frequently in the quadriceps and

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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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Grant E. Norte, Katherine R. Knaus, Chris Kuenze, Geoffrey G. Handsfield, Craig H. Meyer, Silvia S. Blemker and Joseph M. Hart

exclusively limited to the thigh musculature and thereby fail to describe complete lower-extremity function in these cohorts. Altered loading patterns are well described after ACL injury, 36 which inherently influence skeletal muscle function away from the knee. Understanding changes in muscle after ACL

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Akihiro Tamura, Kiyokazu Akasaka and Takahiro Otsudo

landing may cause ACL injuries. 9 Loads on knee joints during landings can be decreased by employing strategies to absorb landing stresses throughout the lower-extremities. Some researchers have measured the relative contributions of the lower-extremity joints for energy absorption during landing. 10

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Shiho Goto, Naoko Aminaka and Phillip A. Gribble

, 20 Finally, activity of the knee extensors has been shown to contribute to frontal plane knee motion stability. 21 , 22 This collective evidence suggests that comprehensive investigation of lower-extremity muscle activity along with kinematics may provide a better understanding of the relationship

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Christie Powell, Jody Jensen and Samantha Johnson

injury, many athletes are not fully recovered and return to play prematurely. Common intrinsic risk factors for lower-extremity injuries are previous injury in the same body region and compromised function. 3 , 6 Previously injured athletes often lack the neuromuscular control, balance, proprioception

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Scott J. Dankel, Jeremy P. Loenneke and Paul D. Loprinzi

Previous research has demonstrated that having adequate lower extremity and upper body muscle strength (generally defined as averting the lower tertile or quartile) reduces the risk of all-cause mortality 1 – 3 ; however, less overt is the importance of skeletal muscle strength on cancer