Chen-Yi Song

Surplus Value of Hip Adduction in Leg-Press Exercise in Patients With Patellofemoral Pain Syndrome: A Randomized Controlled Trial

Background: A common treatment for patients with patellofemoral pain syndrome (PFPS) is strength (force-generating capacity) training of the vastus medialis oblique muscle (VMO). Hip adduction in conjunction with knee extension is commonly used in clinical practice; however, evidence supporting the efficacy of this exercise is lacking. Objective: The objective of this study was to determine the surplus effect of hip adduction on the VMO. Design: This study was a randomized controlled trial. Setting: The study was conducted in a kinesiology laboratory. Participants: Eighty-nine patients with PFPS participated. Intervention: Participants were randomly assigned to 1 of 3 groups: hip adduction combined with leg-press exercise (LPHA group), leg-press exercise only (LP group), or no exercise (control group). Training consisted of 3 weekly sessions for 8 weeks. Measurements: Ratings of worst pain as measured with a 100-mm visual analog scale (VAS-W), Lysholm scale scores, and measurements of VMO morphology (including cross-sectional area [CSA] and volume) were obtained before and after the intervention. Results: Significant improvements in VAS-W ratings, Lysholm scale scores, and VMO CSA and volume were observed after the intervention in both exercise groups, but not in the control group. Significantly greater improvements for VAS-W ratings, Lysholm scale scores, and VMO volume were apparent in the LP group compared with the control group. There were no differences between the LP and LPHA groups for any measures. Limitations: Only the VMO was examined by ultrasonography. The resistance level for hip adduction and the length of intervention period may have been inadequate to induce a training effect. Conclusions: Similar changes in pain reduction, functional improvement, and VMO hypertrophy were observed in both exercise groups. Incorporating hip adduction with leg-press exercise had no impact on outcome in patients with PFPS.

Quadricep and hamstring activation during drop jumps with changes in drop height

OBJECTIVEnCompare the muscle activation patterns of the quadricep-hamstring during drop jumps with increasing demands of drop heights.nnnDESIGNnObservational.nnnSETTINGnUniversity biomechanics laboratory.nnnPARTICIPANTSnFifteen male and eight female college physical education students.nnnMAIN OUTCOME MEASURESnElectromyographic activity of the rectus femoris (RF) and biceps femoris (BF) during the landing and takeoff phase of drop jumps from 20 to 60-cm heights. The ground contact time, vertical ground reaction force (vGRF), knee flexion angle during ground contact, and jump height after takeoff were also analyzed.nnnRESULTSnThe activation of RF was higher in the drop jump from 60-cm than that from 20- and 30-cm (comparing 107.0 ± 45.9 to 82.3 ± 30.8 and 88.9 ± 38.9 %MVIC, P<.05) during the landing phase. Activation of BF remained similar across all drop heights. Drop jump from 60-cm resulted in greater contact time during takeoff phase and peak vGRF, and resulted in greater maximum knee flexion but straighter knee at ground contact than from lower drop heights.nnnCONCLUSIONnAt drop height of 60-cm, the altered knee muscular activation and movement patterns may diminish the effectiveness of plyometric training and increase the potential injury risk of knee.

Muscle activation of vastus medialis obliquus and vastus lateralis during a dynamic leg press exercise with and without isometric hip adduction

OBJECTIVESnTo investigate the effects of submaximal and vigorous isometric hip adduction on the vastus medialis obliquus (VMO) and vastus lateralis (VL) activity during the leg press exercise from 90° of knee flexion until full extension.nnnDESIGNnExperimental.nnnSETTINGnUniversity biomechanics laboratory.nnnPARTICIPANTSnTen healthy male college students.nnnMAIN OUTCOME MEASURESnElectromyographic (EMG) activation of VMO, VL and hip adductor longus (HAL) of the dominant leg were recorded during double leg press (LP), leg press with submaximal isometric hip adduction force (LP+), and leg press with vigorous isometric hip adduction force (LP++). The VMO, VL muscle activation, as well as the VMO/VL ratio between different leg press exercises were analyzed by MANOVA over concentric and eccentric phases, and in 15° increments of knee flexion motion. The effect size was calculated.nnnRESULTSnNeither LP+ nor LP++ changed the overall VMO-VL activation patterns. Specific to knee angle, however, small to medium effect size was shown with incorporation of isometric hip adduction to the leg press exercise for VMO/VL ratio.nnnCONCLUSIONnTargeted training using the leg press exercise to the last 45° of knee extension/flexion with vigorous hip adduction may be useful in promoting a greater VMO/VL ratio.

Influences of Patellofemoral Pain and Fatigue in Female Dancers during Ballet Jump-Landing

This study investigated the influence of patellofemoral pain (PFP) and fatigue on lower-extremity joint biomechanics in female dancers during consecutive simple ground échappé. 3-dimensional joint mechanics were analyzed from the no-fatigue to fatigue conditions. 2-way mixed ANOVAs were used to compare the differences of the kinematic and kinetic variables between groups and conditions. Group main effects were seen in increased jump height (p=0.03), peak vertical ground reaction force (p=0.01), knee joint power absorption (p=0.04), and patellofemoral joint stress (PFJS, p=0.04) for PFP group. Fatigue main effects were found for decreased jump height (p<0.01), decreased ankle plantarflexion at initial foot-ground contact (p=0.01), and decreased ankle displacement (p<0.01). Hip external rotation impulse and hip joint stiffness increased (both p<0.01) while knee extension and external rotation moment, and ankle joint power absorption decreased (p<0.01, p=0.02, p<0.01, respectively) after fatigue. The peak PFJS also decreased after fatigue (p<0.01). Female ballet dancers with PFP sustained great ground impact and loads on the knee probably due to higher jump height compared to the controls. All dancers presented diminished knee joint loading for the protective mechanism and endurance of ankle joint musculature required for the dissipation of loads and displayed a distal-to-proximal dissipation strategy after fatigue.

Validation of In Vivo Patellar Tracking with a Custom-Made Clamp: A Fluoroscopy Study

Evaluation of patellar tracking has been suggested as an increasingly relevant diagnostic tool in patients with patellofemoral disorders. This study aimed to assess the accuracy of measuring in vivo patellar tracking with the use of a custom-made clamp. Nine healthy female college students participated. Sagittal-view fluoroscopy was used to track the movement of the clamp and the underlying patella of each subjects dominant leg during a lunge. The movement patterns (tilt angle and displacement) as well as the absolute angle/distance between the patella and clamp were investigated at 7 knee flexion angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°). The patella and clamp showed similar movement patterns (tilt angle: r= 0.94, P= 0.002; displacement: r= 0.90, P= 0.007). The root mean squared error of less than 3.5° and 0.6 cm were identified below knee flexion 60°. The absolute angle significantly changed at knee flexion 90° compared to 0° (P= 0.016). The absolute distance between the upper edge of the patella and clamp significantly changed at knee flexion 60° to 90° as compared to 0° (all P< 0.05). The angle/distance change may represent an influence of a skin motion artifact manifesting beyond knee flexion 60°. With careful consideration, the custom-made clamp may offer reasonably accurate representations of patellar motion that can be used to further study patella pathologies and develop computational models.

Comparisons of Quadriceps Strength Training, Taping, and Stretching on Clinical Outcomes in Patients with Patellofemoral Pain Syndrome

INTRODUCTION Patellofemoral pain syndrome ( PFPS ) is a common knee disorder. Factors that cause patellofemoral pain include: over use, soft tissue imbalance, and malalignment of lower extremity. Patients with patellofemoral pain, caused by soft tissue imbalance was thought to be favorite to receive physical therapies. Clinically, physical therapies for patients with PFPS are including: Quadriceps strength training, taping, and stretching exercise. The aforementioned treatment tools showed different effect mechanism. However, there were few clinical studies to compare the clinical effects among the aforementioned three treatment tools. The purpose of this study was to investigate the different effects among the quadriceps strength training, taping, and stretching exercise of iliotibial band in patients with patellofemoral pain syndrome by randomized control trial study.

Optimum Drop Jump Height in Division III Athletes: Under 75% of Vertical Jump Height

Our purpose was to evaluate the vertical ground reaction force, impulse, moments and powers of hip, knee and ankle joints, contact time, and jump height when performing a drop jump from different drop heights based on the percentage of a performers maximum vertical jump height (MVJH). Fifteen male Division III athletes participated voluntarily. Eleven synchronized cameras and two force platforms were used to collect data. One-way repeated-measures analysis of variance tests were used to examine the differences between drop heights. The maximum hip, knee and ankle power absorption during 125%MVJH and 150%MVJH were greater than those during 75%MVJH. The impulse during landing at 100%MVJH, 125%MVJH and 150%MVJH were greater than 75%MVJH. The vertical ground reaction force during 150%MVJH was greater than 50%MVJH, 75%MVJH and 100%MVJH. Drop height below 75%MVJH had the most merits for increasing joint power output while having a lower impact force, impulse and joint power absorption. Drop height of 150%MVJH may not be desirable as a high-intensity stimulus due to the much greater impact force, increasing the risk of injury, without increasing jump height performance.