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.

Biomechanical comparisons of single- and double-legged drop jumps with changes in drop height.

The purpose of this study was to compare the biomechanics of single- and double-legged drop jumps (SDJ vs. DDJ) with changes in drop height. Jumping height, ground contact time, reactive strength index, ground reaction force, loading rate of ground reaction force, joint power and stiffness were measured in 12 male college students during SDJ from 20-, 30-, 40-, and 50-cm heights and DDJ from of 20- and 40-cm heights. The peak impact force was increased with the incremental drop height during SDJs. The jumping height and leg and ankle stiffness of SDJ30 were greater than those of SDJ40 and SDJ50. The knee and hip stiffnesses of SDJ30 were greater than those of SDJ50. The impact forces of SDJ30-50 were greater than those of DDJ40. The leg, ankle, knee and hip joint stiffnesses of SDJ20-30 were greater than those of DDJ20 and DDJ40. The propulsive forces of SDJ20-50 were greater than those of DDJ20 and DDJ40. The jumping height of SDJ30 was greater than that of DDJ20. Drop height of 30 cm was recommended during single-legged drop jump with the best biomechanical benefit. Single-legged drop jump from 20-30 cm could provide comparable intensity to double-legged drop jump from 40 cm.

Amphipathic peptides can act as an anticoagulant by competing with phospholipid membranes for blood coagulation factors.

An ideal amphipathic peptide (IAP), composed of simply lysine and leucine residues in a 1:2 ratio (K(7)L(15)), specifically prolongs in vitro coagulation assays that use phospholipids, such as the activated partial thromboplastin time (APTT). The main hypothesis of the present work is that IAP's anticoagulant effect occurs by competing with phospholipid membranes in in vitro coagulation reactions. We verified this hypothesis by employing different phospholipid-dependent coagulation assays, such as the APTT, the dilute prothrombin time (dPT) and the dilute Russell viper venom time (dRVVT) with both low and high amounts of phospholipids. We show that coagulation times are prolonged by IAP in a concentration-dependent manner, and that this prolongation is abrogated by adding excess phospholipid, demonstrating a phospholipid dependence for this inhibition. Using an ELISA-based binding assay, we show IAP inhibits the binding of one of the vitamin K-dependent coagulation factors, factor X, to phospholipid membranes. This is further confirmed with fluorescence spectroscopy, where the interaction of IAP and factor X is inhibited by phospholipid. In summary, this work demonstrates that IAP can act as an anticoagulant by impairing the interaction of coagulation factors with phospholipid membranes and provides a paradigm for the development of novel anticoagulants.

Normal range values for thromboelastography in healthy adult volunteers

Thromboelastography (TEG®) provides a functional evaluation of coagulation. It has characteristics of an ideal coagulation test for trauma, but is not frequently used, partially due to lack of both standardized techniques and normal values. We determined normal values for our population, compared them to those of the manufacturer and evaluated the effect of gender, age, blood type, and ethnicity. The technique was standardized using citrated blood, kaolin and was performed on a Haemoscope 5000 device. Volunteers were interviewed and excluded if pregnant, on anticoagulants or having a bleeding disorder. The TEG® parameters analyzed were R, K, á, MA, LY30, and coagulation index. All volunteers outside the manufacturer’s normal range underwent extensive coagulation investigations. Reference ranges for 95 percent for 118 healthy volunteers were R: 3.8-9.8 min, K: 0.7-3.4 min, á: 47.8-77.7 degrees, MA: 49.7-72.7 mm, LY30: -2.3-5.77 percent, coagulation index: -5.1-3.6. Most values were significantly different from those of the manufacturer, which would have diagnosed coagulopathy in 10 volunteers, for whom additional investigation revealed no disease (81 percent specificity). Healthy women were significantly more hypercoagulable than men. Aging was not associated with hypercoagulability and East Asian ethnicity was not with hypocoagulability. In our population, the manufacturer’s normal values for citrated blood-kaolin had a specificity of 81 percent and would incorrectly identify 8.5 percent of the healthy volunteers as coagulopathic. This study supports the manufacturer’s recommendation that each institution should determine its own normal values before adopting TEG®, a procedure which may be impractical. Consideration should be given to a multi-institutional study to establish wide standard values for TEG®.

Normal range values for thromboelastography in healthy adult volunteers.

Thromboelastography (TEG) provides a functional evaluation of coagulation. It has characteristics of an ideal coagulation test for trauma, but is not frequently used, partially due to lack of both standardized techniques and normal values. We determined normal values for our population, compared them to those of the manufacturer and evaluated the effect of gender, age, blood type, and ethnicity. The technique was standardized using citrated blood, kaolin and was performed on a Haemoscope 5000 device. Volunteers were interviewed and excluded if pregnant, on anticoagulants or having a bleeding disorder. The TEG parameters analyzed were R, K, alpha, MA, LY30, and coagulation index. All volunteers outside the manufacturer's normal range underwent extensive coagulation investigations. Reference ranges for 95% for 118 healthy volunteers were R: 3.8-9.8 min, K: 0.7-3.4 min, alpha: 47.8-77.7 degrees, MA: 49.7-72.7 mm, LY30: -2.3-5.77%, coagulation index: -5.1-3.6. Most values were significantly different from those of the manufacturer, which would have diagnosed coagulopathy in 10 volunteers, for whom additional investigation revealed no disease (81% specificity). Healthy women were significantly more hypercoagulable than men. Aging was not associated with hypercoagulability and East Asian ethnicity was not with hypocoagulability. In our population, the manufacturer's normal values for citrated blood-kaolin had a specificity of 81% and would incorrectly identify 8.5% of the healthy volunteers as coagulopathic. This study supports the manufacturer's recommendation that each institution should determine its own normal values before adopting TEG, a procedure which may be impractical. Consideration should be given to a multi-institutional study to establish wide standard values for TEG.