Influence of Passive Joint Stiffness on Proprioceptive Acuity in Individuals With Functional Instability of the Ankle.

Study Design Controlled laboratory study, cross-sectional. Background Deficits in ankle proprioceptive acuity have been reported in persons with functional instability of the ankle. Passive stiffness has been proposed as a possible mechanism underlying proprioceptive acuity. Objective To compare proprioceptive acuity and passive ankle stiffness in persons with and without functional ankle instability, and to assess the influence of passive joint stiffness on proprioceptive acuity in persons with functional ankle instability. Methods A sample of 18 subjects with and 18 without complaints of functional ankle instability following lateral ankle sprain participated. An isokinetic dynamometer was used to compare motion perception threshold, passive position sense, and passive ankle stiffness between groups. To evaluate the influence of passive stiffness on proprioceptive acuity, individuals in the lateral functional ankle instability group were divided into 2 subgroups: "high" and "low" passive ankle stiffness. Results The functional ankle instability group exhibited increased motion perception threshold when compared with the corresponding limb of the control group. Between-group differences were not found for passive position sense and passive ankle stiffness. Those in the functional ankle instability group with higher passive ankle stiffness had smaller motion perception thresholds than those with lower passive ankle stiffness. Conclusion Unlike motion perception threshold, passive position sense is not affected by the presence of functional ankle instability. Passive ankle stiffness appears to influence proprioceptive acuity in persons with functional ankle instability. J Orthop Sports Phys Ther 2017;47(12):899-905. Epub 7 Oct 2017. doi:10.2519/jospt.2017.7030.

Myofascial force transmission in the lower limb: An in vivo experiment.

Anatomical studies have shown structural continuity between the lumbopelvic region and the lower limb. The present study aimed to verify how simultaneous changes on knee/hip positions modify the ankle's resting position and passive torque. Thirty-seven subjects underwent an isokinetic assessment of ankle passive torque. The relationship between the absolute values of ankle passive resistance torque and the ankle angular position was used to calculate the dependent variables: ankle resting position (position in which the passive resistance torque is zero); and ankle passive torque at 0° (torque at the neutral position of the ankle in the sagittal plane). These measures were carried out under three test conditions: 0° at knee and 0° at hip (0°/0°); 90° at knee and 90° at hip (90°/90°); and, 135° at knee and 120° at hip (135°/120°). The results demonstrated that the ankle resting position shifted towards dorsiflexion when knee/hip position changed from 0°/0° to 90°/90° and shifted towards plantar flexion when knee/hip position changed from 90°/90° to 135°/120°, achieving values close to the ones at the position 0°/0°. Similarly, passive torque reduced when knee/hip position changed from 0°/0° to 90°/90°, but it increased when knee/hip position changed from 90°/90° to 135°/120°. The unexpected changes observed in ankle passive torque and resting position due to changes in knee and hip from 90°/90° to 135°/120°, cannot be explained exclusively by forces related to tissues crossing the knee and ankle. This result supports the existence of myofascial force transmission among lower limb joints.

A quick and reliable procedure for assessing foot alignment in athletes.

BACKGROUND: Quick procedures with proper psychometric properties that can capture the combined alignment of the foot-ankle complex in a position that may be more representative of the status of the lower limb during ground contact are essential for assessing a large group of athletes. METHODS: The assessed lower limb was positioned with the calcaneus surface facing upward in a way that all of the marks could be seen at the center of the camera display. After guaranteeing maintenance of the foot at 90° of dorsiflexion actively sustained by the athlete, the examiner took the picture of the foot-ankle alignment. RESULTS: Intraclass correlation coefficients ranging from 0.82 to 0.93 demonstrated excellent intratester and intertester reliability for the proposed measurements of forefoot, rearfoot, and shank-forefoot alignments. The intraclass correlation coefficient between the shank-forefoot measures and the sum of the rearfoot and forefoot measures was 0.98, suggesting that the shank-forefoot alignment measures can represent the combined rearfoot and forefoot alignments. CONCLUSIONS: This study describes a reliable and practical measurement procedure for rearfoot, forefoot, and shank-forefoot alignments that can be applied to clinical and research situations as a screening procedure for risk factors for lower-limb injuries in athletes.

Avaliação muscular isocinética da articulação do joelho em atletas das seleções brasileiras infanto e juvenil de voleibol masculino / Isokinetic muscle evaluation of the knee joint in athletes of the Under-19 and Under-21 Male Brazilian National Volleyball Team

O salto vertical é inerente à prática do voleibol e demanda grande capacidade de geração de força e trabalho da musculatura envolvida, principalmente do músculo quadríceps. Devido a esta demanda, desequilíbrios entre os músculos extensores e flexores podem estar presentes, levando à sobrecarga das estruturas musculotendíneas da articulação do joelho. Sendo assim, torna-se necessário o estabelecimento de parâmetros de função muscular relacionados a esta articulação em atletas de voleibol. Portanto o objetivo do presente estudo foi avaliar, através de dinamometria isocinética, torque máximo, trabalho máximo, razão agonista/antagonista e índice de fadiga de flexores e extensores de joelho em duas categorias do voleibol. Os testes isocinéticos de flexão e extensão do joelho foram realizados no modo concêntrico-concêntrico, na posição sentada, nas velocidades de 60 e 300°/s em 36 atletas (20 da categoria Infanto-Juvenil e 16 da Juvenil). Os dados possibilitaram estabelecer parâmetros de função muscular da articulação do joelho em atletas das Seleções Brasileiras Infanto-Juvenil e Juvenil de Voleibol Masculino do ano de 2003. Estes atletas apresentaram valores de torque máximo e trabalho máximo normalizados pela massa corporal para quadríceps superiores às médias da população de atletas e não-atletas. Quando comparadas as categorias, os atletas juvenis apresentaram significativamente valores maiores de razão agonista/antagonista e trabalho máximo de flexores de joelhos na velocidade de 60°/s. Além disso, a razão agonista/antagonista foi inferior ao valor de referência esperado em ambas as categorias, caracterizando a predominância da musculatura extensora sobre a flexora. O índice de fadiga encontra-se próximo ao esperado para a maior parte dos atletas. O presente estudo pode servir de base para comparações em futuros estudos que avaliem a função muscular isocinética de atletas de voleibol.

The vertical jump is a basic volleyball practice that demands a high ability to generate strength and work in the muscles involved, mainly in the quadriceps muscle. Due to such demand, muscle imbalances between extensor and flexor muscles may be present, causing an overloading on the muscle-tendinous structures of the knee joint. Thus, the establishment of normal parameters for the muscle function related to that joint in volleyball athletes is necessary. Therefore, the purpose of this study was to assess through isokinetic dynamometry the peak torque, work peak, agonist/antagonist ratio, and fatigue index of the flexor and extensor of the knee among both volleyball athlete population. The isokinetic flexion and extension tests of the knees were performed in the concentric-concentric seat mode at 60 and 300°/sec. velocity in thirty-six athletes (20 under 19-under 21, and 16 under 21). The data allowed to set the parameters for the muscle function of the knee joint among athletes of the 2003 Under 19-Under 21 and Under 21 Brazilian National Team Selection of Male Volleyball. Athletes presented peak torque and work peak values normalized by the body mass to the upper quadriceps to the mean normal values for the athletes and non-athletes populations. Compared to other categories, the under 21 athletes presented significantly higher values for the agonist/antagonist ratio, and peak work ratio of the knee flexors at 60°/sec. velocity. Furthermore, the agonist/antagonist ratio was lower than the reference value expected for both categories, thus characterizing predominance in the extensor musculature over the flexor musculature. The fatigue index was close to what would be expected for the majority of athletes. The present study may be useful as comparison basis for future studies aiming evaluate the isokinetic muscle function in volleyball players.

El salto vertical es inherente a la práctica del voleibol y demanda la gran capacidad de generación de fuerza y trabajo de la musculatura comprendida, principalmente del músculo quadríceps. Debido a esta demanda, los desequilibrios entre los músculos extensores y flexores pueden estar presentes, sumando a ello, la carga excesiva de las estructuras músculo-tendíneas de la articulación de la rodilla. Por estos motivos resulta necesario, el establecimiento de parámetros de función muscular relacionados con esta articulación en atletas del voleibol. Por consiguiente el objetivo del estudio presente fue evaluar, a través de la dinamometria isocinética, el patrón del torque máximo, trabajo máximo, razón agonista/antagonista y el índice de fatiga de los flexores y extensores de la rodilla en dos categorías del voleibol. Los tests isocinéticos de flexión y extensión de las rodillas fueron cumplidas de la manera concéntrico-concéntrica, en la posición asiento, en las velocidades de 60 y 300°/s en 36 atletas (20 de la categoría Infanto-juvenil y 16 del juvenil). Los datos hicieron posible establecer parámetros de función muscular de la articulación de la rodilla en atletas de las Selecciones brasileñas Infanto-Juvenil y Juvenil de Voleibol Masculino del año 2003. Estos atletas presentaron los valores de torque máximo y el trabajo máximo normalizados por la masa corpórea para el quadríceps superior a los promedios de la población de los atletas y no-atletas. Cuando se compararon las categorías, los atletas juveniles presentaron valores más grandes de relación agonista/antagonista y de trabajo del máximo de flexores de rodillas significativamente en la velocidad de 60°/s. Además de esto, la relación agonista/antagonista era inferior al valor de la referencia esperado en ambas categorías, caracterizando el predominio de la musculatura extensora sobre la flexora. El índice de fatiga está cerca de lo esperado para la mayoría de los atletas. El estudio...