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Taija Finni and Sulin Cheng

The positions of EMG electrodes over the knee extensor muscles were examined in 19 healthy men using MR images; electrodes were placed according to the SENIAM (surface electromyography for non-invasive assessment of muscles) guidelines. From axial images, the medial and lateral borders of the muscles were identified, and the arc length of the muscle surface was measured. The electrode location was expressed as a percentage value from the muscle’s medial border. EMGs were recorded during isometric maximal contraction, squat jumps, and countermovement jumps and analyzed for cross-correlation. The results showed that variations in lateral positioning were greatest in vastus medialis (47% SD 11) and rectus femoris (68% SD 15). In vastus lateralis, the electrode was usually placed close to the rectus femoris (19% SD 6). The peak cross-correlation coefficient varied between 0.15 and 0.68, but was not associated with electrode location. It is recommended that careful consideration is given to the medial-lateral positioning of the vastus lateralis electrodes especially, so that the electrodes are positioned over the mid-muscle rather than in close proximity to rectus femoris.

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Erwin E.H. van Wegen, Richard E.A. van Emmerik, Robert C. Wagenaar and Terry Ellis

Postural instability is a major problem in patients with Parkinson's disease (PD). We examined balance control in PD by using center of pressure (CP) variability and time-to-contact to investigate boundary relevant postural control behavior under quiet stance leaning conditions. Postural orientation was manipulated by having patients (n = 10) and healthy older controls (n = 7)lean Forward and backward with varying degrees of lean on a force platform. The subjects were instructed to lean forward or backward (either halfway or as far as possible) without bending their hips or lifting their heels or toes off the ground. Time-to-contact of the CP with the geometric stability boundary defined by the feet as well as CP position and variability were analyzed. Mediolateral CP variability was increased in the patients with PD. Medio-lateral average time-to-contact was decreased in the patients but not so in the antcrior-posterior direction. In contrast to the CP variability, the medio-lateral variability of time-lo-contact was lower in the patients. Patients as well as healthy older controls responded to lean manipulations with an increase in CP variability. Boundary relevant CP measures thus show clear changes in control strategies and confirm the role of lateral instability in PD.

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Fatemeh Ehsani, Rozita Hedayati, Rasool Bagheri and Shapour Jaberzadeh

, showing good internal consistency. 39 Lateral Abdominal Muscle Thickness For measuring the thickness of deep lateral abdominal muscles (TrA and IO) and the superficial lateral abdominal muscle (external oblique [EO] muscle), a diagnostic US imaging unit (HS-2100, Honda, Japan) set in B-mode with a 7.5-MHz

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Ken Tokunaga, Yuki Nakai, Ryo Matsumoto, Ryoji Kiyama, Masayuki Kawada, Akihiko Ohwatashi, Kiyohiro Fukudome, Tadasu Ohshige and Tetsuo Maeda

This study evaluated the effect of foot progression angle on the reduction in knee adduction moment caused by a lateral wedged insole during walking. Twenty healthy, young volunteers walked 10 m at their comfortable velocity wearing a lateral wedged insole or control flat insole in 3 foot progression angle conditions: natural, toe-out, and toe-in. A 3-dimensional rigid link model was used to calculate the external knee adduction moment, the moment arm of ground reaction force to knee joint center, and the reduction ratio of knee adduction moment and moment arm. The result indicated that the toe-out condition and lateral wedged insole decreased the knee adduction moment in the whole stance phase. The reduction ratio of the knee adduction moment and the moment arm exhibited a close relationship. Lateral wedged insoles decreased the knee adduction moment in various foot progression angle conditions due to decrease of the moment arm of the ground reaction force. Moreover, the knee adduction moment during the toe-out gait with lateral wedged insole was the smallest due to the synergistic effect of the lateral wedged insole and foot progression angle. Lateral wedged insoles may be a valid intervention for patients with knee osteoarthritis regardless of the foot progression angle.

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Yuki Uto, Tetsuo Maeda, Ryoji Kiyama, Masayuki Kawada, Ken Tokunaga, Akihiko Ohwatashi, Kiyohiro Fukudome, Tadasu Ohshige, Yoichi Yoshimoto and Kazunori Yone

The purpose of this study was to determine whether a lateral wedge insole reduces the external knee adduction moment during slope walking. Twenty young, healthy subjects participated in this study. Subjects walked up and down a slope using 2 different insoles: a control flat insole and a 7° lateral wedge insole. A three-dimensional motion analysis system and force plate were used to examine the knee adduction moment, the ankle valgus moment, and the moment arm of the ground reaction force to the knee joint center in the frontal plane. The lateral wedge insole significantly decreased the moment arm of the ground reaction force, resulting in a reduction of the knee adduction moment during slope walking, similar to level walking. The reduction ratio of knee adduction moment by the lateral wedge insole during the early stance of up-slope walking was larger than that of level walking. Conversely, the lateral wedge insole increased the ankle valgus moment during slope walking, especially during the early stance phase of up-slope walking. Clinicians should examine the utilization of a lateral wedge insole for knee osteoarthritis patients who perform inclined walking during daily activity, in consideration of the load on the ankle joint.

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Jana Fleischmann, Guillaume Mornieux, Dominic Gehring and Albert Gollhofer

Sideward movements are associated with high incidences of lateral ankle sprains. Special shoe constructions might be able to reduce these injuries during lateral movements. The purpose of this study was to investigate whether medial compressible forefoot sole elements can reduce ankle inversion in a reactive lateral movement, and to evaluate those elements’ influence on neuromuscular and mechanical adjustments in lower extremities. Foot placement and frontal plane ankle joint kinematics and kinetics were analyzed by 3-dimensional motion analysis. Electromyographic data of triceps surae, peroneus longus, and tibialis anterior were collected. This modified shoe reduced ankle inversion in comparison with a shoe with a standard sole construction. No differences in ankle inversion moments were found. With the modified shoe, foot placement occurred more internally rotated, and muscle activity of the lateral shank muscles was reduced. Hence, lateral ankle joint stability during reactive sideward movements can be improved by these compressible elements, and therefore lower lateral shank muscle activity is required. As those elements limit inversion, the strategy to control inversion angles via a high external foot rotation does not need to be used.

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Bram L. Newman, Courtney L. Pollock and Michael A. Hunt

Context: Lateral trunk-flexion strength is an important determinant of overall trunk stability and function, but the reliability in measuring this outcome clinically in athletic individuals is not known. Objective: To determine the interrater and intrarater reliability of lateral trunk-flexion strength measurement in athletic individuals using handheld dynamometry. Design: Reliability study. Setting: Research laboratory. Participants: 12 healthy, athletic individuals. Intervention: Lateral trunk-flexion strength was measured using handheld dynamometry across 2 different trunk placements (lateral aspect of the axilla and laterally at the level of the midtrunk) and 2 testing occasions by 2 therapists. Three maximum-effort trials during a "make test" at each placement were completed for each therapist on both occasions. Main Outcome Measures: Maximum force output was identified and converted to a torque. Intraclass correlation coefficients (ICC2,1) were calculated for each dynamometer placement, therapist, and test occasion to determine intrarater and interrater reliability. Results: Intrarater reliability was moderate to good (ICC2,1 = .53-.77), while interrater reliability was good to very good (ICC2,1 = .79-81) at the axilla position. For the midtrunk position, intrarater reliability was good to very good (ICC2,1 = .80-.86), while interrater reliability was good on both days (ICC2,1 = .87-.88). Finally, the standard errors of measurement were low for the axilla position (0.20 Nm/kg; 95% CI .15, .28) and midtrunk position (0.09 Nm/kg; 95% CI .07, .12). Conclusions: Maximum lateral trunk-flexion strength can be reliably measured in athletic individuals with greater overall strength. Based on the 2 positions used in this study, measurement with a dynamometer placement at the midtrunk may be more reliable than that obtained at the axilla.

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Dennis A. Nowak, Joachim Hermsdörfer and Helge Topka

Amyotrophic lateral sclerosis is a degenerative motor neuron disorder with progressive and exclusive loss of motor neurons in the spinal cord, brainstem, and motor cortex. Five patients with amyotrophic lateral sclerosis, and 5 age-matched, healthy control subjects performed vertical point-to-point arm movements with an instrumented hand-held object. In between the movements, the object was held stationary. Compared with healthy controls, all patients generated greater grip forces during the phase of stationary holding of the object and greater ratios between grip and load force maximums during the arm movements. We conclude that in amyotrophic lateral sclerosis, the ability to scale the grip force magnitude efficiently according to the actual loading requirements is impaired. When performing upward movements, controls increased grip force in parallel with load force right from the movement onset; during downward movements, controls anticipated an early decrease of load force by constant or decreasing grip forces. In contrast, 3 of 5 patients showed an early increase of grip force during both upward and downward movements, indicating that in amyotrophic lateral sclerosis, the differential regulation of the grip force output according to the direction-dependent load force profile may be impaired. In motor neuron disease, the inaccurate grip force scaling and the impaired temporal coupling between grip and load force profiles may either directly result from deficient motor execution or be secondary to accompanying symptoms, such as dyscoordination of hand and finger muscles due to spasticity.

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Dario I. Carrasco, John Lawrence III and Arthur W. English

The primary purpose of this study was to establish whether the neuromuscular compartments of cat lateral gastrocnemius produce different mechanical actions on the skeletal system, by determining the contributions made by these compartments to the torques produced about the ankle joint. It was postulated that neuromuscular compartments might represent output elements of the spinal circuits. If so, they should produce unique mechanical actions. Isometric torques about the center of the ankle joint produced by the neuromuscular compartments of the cat lateral gastrocnemius were measured with a multiaxis force-moment sensor connected to the plantar surface of the foot. Individual compartment torques were elicited by activation of the primary compartment branches of the lateral gastrocnemius nerve. The magnitude of the individual torque components, and thus of the resultant torque, was significantly different between compartments. In three of the four lateral gastrocnemius compartments, significantly different torque trajectories were noted. The results, together with those from previous studies demonstrating that compartments can be activated in a task-dependent manner, suggest that neuromuscular compartments represent anatomical substrates that can be used by the nervous system for regulating movement.

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Simon M. Luethi, Edward C. Frederick, Michael R. Hawes and Benno M. Nigg

The purpose of this study was to analyze the influence of footwear on the kinematics and the mechanical load on the lower extremities during fast lateral movements in tennis. The method used was a prospective study. Two types of tennis shoes were randomly distributed among 229 tennis players. The subjects were measured before starting a 3-month test period. The study showed that the kinematics of the lower extremities and internal load conditions during fast lateral movements in tennis are highly influenced by the type of shoe worn. The results further suggest that a prospective biomechanical analysis can be used to establish assumptions concerning the etiology of pain and injuries in sports related activities.