THE WORK AND ACTIVATION OF LOWER EXTREMITY MUSCLES IN EXPLAINING INTERINDIVIDUAL VARIABILITY IN RUNNING ECONOMY

The purpose of this study was to describe the relationships between RE and the neuromechanics of ground contact. Results of biomechanical studies suggest that more economical runners use different neuromuscular strategies during the stance phase of running. Research in our lab revealed significant, positive correlations between metabolic cost and positive work at the hip and ankle, but significant, negative correlations between metabolic cost and positive work at the knee. Studies focusing on RE and muscle activation patterns show contrasting results. Mechanics may suggest straightforward applications to training and coaching, but further study is required in the area of muscle activation

A BeppoSAX observation of the super-soft source CAL87

We report on a BeppoSAX Concentrator Spectrometer observation of the super-soft source (SSS) CAL87. The X-ray emission in SSS is believed to arise from nuclear burning of accreted material on the surface of a white dwarf (WD). An absorbed blackbody spectral model gives a chi^2_v of 1.18 and a temperature of 42 +/- ^13 _11 eV. However, the derived luminosity and radius are greater than the Eddington limit and radius of a WD. Including an O viii edge at 0.871 keV gives a significantly better fit (at > 95% confidence) and results in more realistic values of the source luminosity and radius. We also fit WD atmosphere models to the CAL87 spectrum. These also give reasonable bolometric luminosities and radii in the ranges 2.7-4.8 10^{36} erg/s and 8-20 10^7 cm, respectively. These results support the view that the X-ray emission from CAL87 results from nuclear burning in the atmosphere of a WD.Comment: 4 pages. Accepted for publication in A&A (Letters

DIFFERENCES IN DYNAMIC STABILIZATION BETWEEN VOLLEYBALL AND RUGBY PLAYERS

The purpose of this study was to examine differences in the time to stabilization (TTS) between volleyball players (n=8) and rugby players (n=7). With no footwear, all participants performed 4 different hopping tasks (medial, lateral, and two forward hops) onto each foot. The AP and ML ground reaction force data were collected and used to compute the TTS for each condition. The TTS measures were averaged within the groups and compared by using eight independent-sample T-tests . Two out of eight conditions showed differences between the volleyball group and the rugby group. The rugby group stabilized more quickly on the R-foot 50% forward hop task (t(13)=3.722, ) and the volleyball group more quickly on the L-foot medial hop task (t(13)=-2.431, )

Carbon Flashes in the Heavy Element Ocean on Accreting Neutron Stars

We show that burning of a small mass fraction of carbon in a neutron star ocean is thermally unstable at low accumulated masses when the ocean contains heavy ashes from the hydrogen burning rapid proton (rp) process. The key to early unstable ignition is the low thermal conductivity of a heavy element ocean. The instability requires accretion rates in excess of one-tenth the Eddington limit when the carbon mass fraction is 0.1 or less. The unstable flashes release 10^{42} to 10^{43} ergs over hours to days, and are likely the cause of the recently discovered large Type I X-ray bursts (so-called ``superbursts'') from six Galactic low mass X-ray binaries. In addition to explaining the energetics, recurrence times, and durations of the superbursts, these mixed carbon/heavy element flashes have an accretion rate dependence of unstable burning similar to that observed. Though the instability is present at accretion rates near Eddington, there is less contrast with the accretion luminosity there, explaining why most detections are made at accretion rates between 0.1 and 0.3 Eddington. Future comparisons of time dependent calculations with observations will provide new insights into the rp process.Comment: Submitted to Astrophysical Journal Letters (6 pages, 3 figures

FRONTAL PLANE KNEE DISPLACEMENT IN BARBELL BACK SQUAT

The aim of the study was to analyze the ML knee displacement and its influence on barbell tilt and rotation displacement from the back squat. Based on the weight distribution (WtD) test, 13 were in the equal WtD group and 14 were in the unequal WtD group. All subjects performed 75% of 1RM barbell back squat with reflective markers on selected locations for motion analysis. Medial-lateral (ML) knee displacement, barbell tilt and rotation displacements were considered. The results showed a statistically significant difference between groups (

THE EFFECT OF COMPRESSION TIGHTS AND DURATION OF TESTING ON CONTINUOUS JUMPING MECHANICAL POWER

INTRODUCTION: In order to improve their performance, athletes seek advancements in technology, such as clothing. Manufacturers of compression tights, advertise that their product adds support to lower extremity musculature, thus may slow the onset of fatigue. Few scientific studies, however, have been conducted to identify how advancements in apparel influence an athlete’s performance (Kraemer et al., 1996). The purpose of the present study was to identify the effects of compression tights on mechanical power for continuous jumping. Secondly, the effect of duration on the mechanical power output by using Bosco’s method (1983) over 15, 30, 45, and 60 sec time-frames, as well as the interaction between apparel and duration

XTE J1739-302: An Unusual New X-ray Transient

A new x-ray transient, designated XTE J1739-302, was discovered with the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) in data from 12 August 1997. Although it was the brightest source in the Galactic Center region while active (about 3.0 x 10^-9 ergs/cm2/s from 2 to 25 keV), it was only observed on that one day; it was not detectable nine days earlier or two days later. There is no known counterpart at other wavelengths, and its proximity to the Galactic Center will make such an identification difficult due to source confusion and extinction. The x-ray spectrum and intensity suggest a giant outburst of a Be/neutron star binary, although no pulsations were observed and the outburst was shorter than is usual from these systems.Comment: 11 pages incorporating 6 figures, AAStex; accepted for The Astrophysical Journal, Part 2 (Letters