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Chaosuan Kanchanomai, Panurungsit Muanjan and Vajara Phiphobmongkol

The effects of locking screw position (long column fixation—long distance between the nearest screws to the fracture—and short column fixation—short distance between the nearest screws to the fracture) and fracture gap size (1-mm and 8-mm transverse fracture gap) on stiffness and fatigue of fractured femur fixed with a locking compression plate (LCP) were biomechanically evaluated. The stiffness of 1-mm fracture gap models and that of intact femoral model were in the range of 270–284 N/mm, while those of 8-mm fracture gap models were significantly lower (155–170 N/mm). After 1,000,000 cycles of loading, no fracture of LCP of 1-mm fracture gap models fixed in either long column or short column fashions occurred. On the other hand, the complete fractures of LCPs of 8-mm fracture gap models fixed in long column and short column fashions occurred after 51,500 and 42,000 cycles of loading, respectively. These results suggest that the full weight loading may be allowed for the patient with 1-mm transverse femoral fracture fixed with an LCP. On the other hand, the full load of walking should be avoided for the patient with 8-mm transverse femoral fracture fixed with an LCP before adequate healing.

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Kentaro Chino and Hideyuki Takahashi

Stiffness is a mechanical measure of a material elasticity defined as the resistance of a material to elongation: greater stiffness means that the material offers greater resistance to a given elongation. 1 , 2 Passive joint stiffness is quantified according to the slope of joint angle

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Olivier Caron, Thierry Gélat, Patrice Rougier and Jean-Pierre Blanchi

The center of foot pressure (CP) motions, representing the net neuromuscular control, was compared to the center of gravity (CG) motions, representing the net performance. The comparison focused on the trajectory path length parameter along the mediolateral and antero-posterior axes because these two variables depend on amplitude versus frequency relationship. This relationship was used to evaluate the CG motions based on the CP motions. Seven subjects stood still on a force plate with eyes open and eyes closed. The results showed that the ratio of (CP – CG)/CP trajectory path length was personal for each subject. These results suggest different levels of passive (ligaments, elastic properties) and active (reflex activity) stiffness. For some subjects, this ratio was significantly lower for the eyes open condition than for the eyes closed condition, indicating a decrease of the active stiffness for the eyes open condition. Therefore, a CG – CP comparative analysis appeared helpful in understanding the control of balance and necessary to quantify the subjects’ net performance.

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Ian M. Greenlund, Piersan E. Suriano, Steven J. Elmer, Jason R. Carter and John J. Durocher

or more hours per day compared with 5 or less hours per day. 4 The relation between sedentary behavior and CVD is complex. Sedentary behavior is shown to increase arterial stiffness and is a known contributor to hypertension and CVD. 5 , 6 Clearly, a reduction in sedentary time and replacement with

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Fabian Mager, Jim Richards, Malika Hennies, Eugen Dötzel, Ambreen Chohan, Alex Mbuli and Felix Capanni

Forefoot stiffness has been shown to influence joint kinematics and kinetics. Willwacher et al 1 found that changes in the stiffness of the metatarsophalangeal joint have a bearing on power generation, push-off duration, and anterior shift of the center of pressure in the second half of stance

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Nicholas Tam, Ross Tucker, Jordan Santos-Concejero, Danielle Prins and Robert P. Lamberts

running economy were discussed. Examples of these include ground-reaction forces (GRFs), swing-phase characteristics, joint stiffness, and foot strike pattern. These too were noted to have a conflicting and/or underinvestigated relationship with running economy, 10 , 11 – 13 although the alignment of the

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Bernard Liew, Kevin Netto and Susan Morris

that is tuned by the motor control system is the stiffness of the “massless” leg spring. Leg stiffness is more accurately a measure of “quasi-stiffness”, as it reflects the ability of the lower limb to oppose externally applied displacements independent of the period of application. 9 , 10 The

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Justin P. Waxman, Kevin R. Ford, Anh-Dung Nguyen and Jeffrey B. Taylor

Measures of lower-extremity stiffness continue to gain popularity in the biomechanics literature due to their reported associations with both athletic performance and lower-extremity injury risk. 1 , 2 For example, higher levels of lower-extremity stiffness have been shown to be predictive of

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Mark A. Sutherlin, L. Colby Mangum, Shawn Russell, Susan Saliba, Jay Hertel and Joe M. Hart

individuals, leading to increased or abnormal forces placed on more proximal structures that could result in injury. Two methods to assess force attenuation during landing could be through a lower-extremity or vertical stiffness 8 – 13 or individual joint stiffness measures. 9 , 10 , 14 Lower

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Simon A. Rogers, Chris S. Whatman, Simon N. Pearson and Andrew E. Kilding

sprinting velocity ( v max ). 2 Recently, profiling and monitoring of running economy (RE) and v max has seen increased interest in mechanical stiffness. Mechanical stiffness is defined as an expression of a systems compressibility during the application of force, such as ground interactions in running