Head Depth and Head Speed During Competitive Backstroke Ledge Starts

Recently, a commercially available starting ‘ledge’ designed to reduce foot slippage during the execution of the backstroke start was introduced in competitive swimming. For the purpose of identifying potential safety consequences, the present study investigated the effect of ledge use on head depths, speeds, and distances in backstroke starts of athletes with no prior or only novice familiarity of the ledge. Competitive backstroke starts were performed with and without ledges by high school-aged (14.5 to 19.2 yr, N = 61) swimmers in 1.52 m of water during a closed testing session. A SIMI Reality Motion System in a calibrated space using three cameras was employed for filming starts. Dependent measures were initial head height (Yset), distance from wall at entry (Xentry), entry angle (Angleentry), horizontal velocity at head entry (XVelentry), resultant velocity at entry (ResVelentry), maximum depth of the center of the head (Ymhd), resultant velocity at maximum head depth (ResVelmhd), and distance from the wall at maximum head depth (Xmhd). The ledge (L) condition showed significant increases compared to the non-ledge (NL) condition in Xentry (L 1.61 ± 0.59 m, NL 1.50 ± 0.53 m, p \u3c .001), ResVelentry (L 3.44 ± 0.97 m·s-1, NL 3.08 ± 1.00 m·s-1, p \u3c .001), Angleentry (L 43.13 ± 16.97°, NL 39.66 ± 18.11°, p = .030), Xmhd (L 4.18 ± 0.58 m, NL 4.09 ± 0.63 m, p = .008), and Ymhd (L 0.54 ± 0.21 m, NL 0.49 ± 0.18,

Measurements of elliptic and triangular flow in high-multiplicity 3^{3}He++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

We present the first measurement of elliptic ($v_2$) and triangular ($v_3$) flow in high-multiplicity $^{3}$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in $^{3}$He$+$Au and in $p$$+$$p$ collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the $^{3}$He$+$Au system. The collective behavior is quantified in terms of elliptic $v_2$ and triangular $v_3$ anisotropy coefficients measured with respect to their corresponding event planes. The $v_2$ values are comparable to those previously measured in $d$$+$Au collisions at the same nucleon-nucleon center-of-mass energy. Comparison with various theoretical predictions are made, including to models where the hot spots created by the impact of the three $^{3}$He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.Comment: 630 authors, 9 pages, 4 figures, 2 tables. v2 is the version accepted for publication by Physical Review Letters. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

The effects of high intensity interval training on resting mean arterial pressure and C-reactive protein content in prehypertensive subjects

Master of ScienceDepartment of KinesiologyCraig A. HarmsSubjects with prehypertension are at risk for developing hypertension (HTN). Hypertension is associated with low-grade systemic inflammation (LGSI). Aerobic exercise training (ET) is a proven means to reduce both blood pressure and LGSI in healthy and diseased subjects. Recently, high intensity interval training (HIIT) has been show to elicit similar cardiovascular and metabolic adaptations as ET in healthy and at-risk populations in a more time efficient manner. Therefore, we hypothesized that HIIT would elicit greater reductions in blood pressure and LGSI than ET. Twelve pre-hypertensive subjects (systolic blood pressure 127.0 ± 8.5 mmHg; diastolic blood pressure 86.2 ± 4.1 mmHg) were randomly assigned to an ET group (n=5) and a HIIT group (n=7). All subjects performed an incremental test to exhaustion (VO2max) on a cycle ergometer prior to, after 4 weeks, and after 8 weeks of training. Resting heart rate and blood pressure were measured prior to and three times a week during training. LGSI was measured via high-sensitivity C-reactive protein (hs-CRP) prior to, after 4 weeks and after 8 weeks of training. ET subjects performed an eight week exercise training program at 40% VO2 reserve determined from the VO2max test, while HIIT subjects performed exercise at 60% peak power determined from the VO2max test. ET group trained four days/week while HIIT trained three days/week. ET exercised for 30 minutes continuously at a constant workload and cadence of 60 rpm while HIIT performed a protocol on a 1:1 work-to-rest ratio at a constant workload and cadence of 100 rpm. Both groups showed similar (p0.05). VO2max increased ~25% with both HIIT and ET with no differences (p>0.05) between groups. These data suggest both HIIT and ET similarly decreased resting blood pressure and increased VO2max while HIIT was effective in decreasing LGSI in subjects who were pre-hypertensive