Knee Muscle Reciprocal Co-Activation in Patellofemoral Pain Syndrome During Isokinetic Exercise: A Voluntary Response Index Analysis

Introduction: The origin of the Patellofemoral Pain Syndrome (PFPS) is not still completely clear and may have a biomechanical or biochemical cause. Motor control dysfunction may have a role in this condition. Voluntary Response Index (VRI) is able to show changes in the central nervous system motor output that occur with intervention, recovery, or progression of the disorder. Therefore, the outcomes may contribute to offer another tool for PFPS motor control evaluation. The aim of the present study, therefore, was to assess the changes in the quadriceps and hamstring reciprocal coactivation patterns that may be observed in individuals with PFPS using the VRI. Methods and Materials: A total of 24 female participants, 12 with sound knees and 12 with PFPS participated in the present study. The study was accomplished in the Biomechanics Laboratory at Rehabilitation School of Tehran University of Medical Sciences in 2015. The participants sat on a Biodex dynamometer. They were asked to perform 10 continuous knee extension and flexion motions with maximal strength at 45˚/s and 300˚/s, distinctly. Simultaneously, electromyographic activities of the vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) were recorded and VRI was calculated. A two-way analysis of variance was run to assess the effect of group and velocity on the VRI (similarity index and magnitude). Results: There was no velocity or group main effect observed for the VRI (P>0.05). In addition, no significant velocity × group interaction was found for the VRI (P>0.05). Conclusion: PFPS may not be linked to altered quadriceps and hamstring reciprocal co-activation patterns during isokinetic exercise. In addition, angular velocity may not be an important parameter in voluntary motor control assessment during isokinetic exercise.Keywords: Reciprocal co-activation; Voluntary response index; Patellofemoral pain syndrome; Isokineti

The Effects of Lower Extremity Muscle Fatigue on Dynamic Balance in Volleyball Players

Objectives: Lower extremity muscles are critical for maintaining dynamic balance and athletic performance. Fatigue of these muscles may affect dynamic balance. It is unclear whether fatigue in a particular muscle group can affect dynamic balance more than that in other groups. This study was conducted to evaluate and compare the effects of fatigue in 5 muscle groups on dynamic balance in volleyball players. Methods: Fifteen healthy male volleyball players separately performed the Star Excursion Balance Test before and immediately after the occurrence of fatigue of ankle Plantar Flexor (PF), knee extensor, knee flexor, hip abductor, and hip adductor muscles. Composite reach distance and distance in anterior, posteromedial, and posterolateral directions were recorded, accordingly. Results: Repeated-measures Analysis of Variance (ANOVA) data indicated that fatigue of all muscle groups significantly decreased the mean score of composite (P<0.001). Anterior, posteromedial, and posterolateral distance scores decreased following muscle fatigue of knee extensors and ankle PFs (P<0.05). Discussion: This study suggested that regarding composite reach score, fatigue of ankle, knee, and hip muscles similarly decreased dynamic balance. However, evaluating three main directions revealed that knee extensors and ankle PFs muscles fatigue presented more prominent effects on the explored volleyball players’ balance, compared to the other muscles

Effects of tension of Kinesio taping application on maximum quadriceps torque and knee repositioning sense in recreationally males

Background: Sports injuries of the knee joint are very common. There are both contact injuries and non-contact injuries. Contractile injuries may be due to an impairment of the knee joint position sense or a decrease of the quadriceps muscle strength. Using a Kinesio taping method may decrease this impairment. The aim of the current study was to assess the effect of direction and tension of Kinesio taping of the quadriceps muscle on repositioning sense of the knee joint and maximum concentric and eccentric torque of the knee extensors. Methods: Twenty-one recreationally active healthy males, determined by convenient non-probability sampling method, participated in this quazi-experimental study. The tests were performed in biomechanics laboratory of School of Rehabilitation of Tehran University of Medical Sciences, Iran, between July to November 2017. They visited biomechanics laboratory 5 sessions. The first session was for familiarization with the main tests and signing an informed consent form. For 2 through 5 sessions, one of each Kinesio tape tension approaches of 100, 115 and 140 percent (origin to insertion direction) and 100 percent (insertion to origin direction) was randomly applied on the quadriceps muscle. Active and passive repositioning sense of the knee joint at 60-degree flexion and maximum concentric and eccentric torque of the knee extensors of the dominant extremity before and after Kinesio taping were measured using a Biodex System 3 isokinetic dynamometer (Biodex Medical Systems, Shirley, NY, USA). Order of measuring active and passive repositioning sense and maximum concentric and eccentric torque of the knee extensors were randomly selected. Results: Origin to insertion Kinesio taping method with tension of 100, 115 and 140 percent significantly decreased means of active and passive repositioning sense errors (P 0.05). Conclusion: According to the results, Kinesio taping could influence on repositioning sense of the knee joint at 60-degree knee flexion. Maximum concentric and eccentric extensor torques was also increased