Intralimb coordination following obstacle clearance during running: the effect of obstacle height.

The purpose of this study was to investigate the different coordination strategies used following obstacle clearance during running. Ten subjects ran over a level surface and over obstacles of six different heights (10, 12.5, 15, 17.5, 20 and 22.5% of their standing height). Analysis based upon the dynamical systems theory (DST) was used and the phasing relationships between lower extremity segments were examined. The results demonstrated that the increasing obstacle height elicited behavioral changes. The foot and the leg became more independent in their actions, while the leg and the thigh strengthened their already stable relationship. The 15% obstacle height seems to be a critical height for the observed changes.

A dynamical systems investigation of lower extremity coordination during running over obstacles.

OBJECTIVE: To investigate intralimb coordination during running over a level surface and over obstacles of three different heights. DESIGN: The phasing relationships between the foot and leg motions in the frontal plane, and the shank and thigh motions in the sagittal plane were used to compare patterns of coordination. BACKGROUND: The coordinated actions of lower extremity segments are necessary to absorb the impact forces generated during running. The behavioral patterns of these segments can be studied under changing task demands using analysis techniques from the Dynamical Systems Theory. METHODS: Ten subjects ran at their self-selected pace under four conditions: over a level surface and over obstacles of different heights (5%, 10%, 15% of their standing height). A force platform was used to record impact forces during landing after obstacle clearance, while kinematics were collected using a two-camera system. RESULTS: The increases in obstacle height resulted in significant changes in impact forces (34% increase between the two extreme conditions) and more in-phase relationships between the segments during early stance. No changes were observed in the variability of the phasing relationships. CONCLUSIONS: The coordination changes observed might be compensatory strategies aimed to reduce forces and potential injury. However, since the impact forces still increased significantly, it is also possible that the observed changes might be at-risk movement patterns predisposing runners to injury.

Oxidation of recombinant methionyl human granulocyte colony stimulating factor.

The oxidation of methionine residues in recombinant methionyl human granulocyte colony stimulating factor with hydrogen peroxide has been investigated. Kinetic data of the oxidation were obtained by using reversed phase-high performance liquid chromatography. The stability-indicating capability of this system was confirmed with micellar electrokinetic capillary chromatography. In the pH range 1.9-7.5, the kobs value for the oxidation process is constant. Above pH 7.5, kobs tends to increase with increasing pH. In the pH range 1.9-11.8, four oxidation products were detected in RP-HPLC. Mass spectrometric analysis revealed that one mono-, one di- and two trioxidation products were formed. Using the cyanogen bromide cleavage method the nature of the oxidation products was determined. The mono-oxidation product is the protein with Met121 oxidized, while the dioxidation product has oxidized Met121 and Met126 residues. The trioxidation products are the proteins with Met121, Met126 and Met137 or Met0, Met121 and Met126 oxidized.