No description available.

No description available.

The purpose of this study was to investigate the effect of prolonged exercise on running economy. Fourteen male long distance runners performed two 90 minute runs on an outdoor 400m track at velocities equal to 65 and 80% of VO$ sb2$max. Prior to and following each 90 minute run, running economy (RE) was measured as the steady-state VO$ sb2$ during treadmill runs at speeds of 188 and 228 m/min. During the 90-min run at 65% of VO$ sb2$max, the mean weight loss was 1.3 kg. The HR was 143 bpm between minutes 5-10 and increased to 150 bpm between minutes 85-90. During the 90-min run at 80% of VO$ sb2$max, the mean weight loss was 1.4 kg. The HR was 161 bpm between minutes 5-10 and increased to 165 bpm between minutes 85-90. When the post RE test was conducted following each 90-min run, there was a significant increase in VO$ sb2$ expressed in both l/min and ml/kg$ cdot$min (a decrease in running economy). The increase in oxygen cost of running following the 90-min run at 80% of VO$ sb2$max was greater than that following the run at 65% of VO$ sb2$max.

The goal of the present investigation was to evaluate the role of the pulmonary diffusion capacity (as measured by DLco) in relation to exercise-induced hypoxemia in elite athletes working at near maximal exercise intensities. Twenty-four elite cyclists were submitted to a direct measurement of VO$ sb2$ max on cycle ergometer which permitted classification into one of two groups. "Desaturaters" (N = 13) if oxyhemoglobin saturation (SaO$ sb2$%), as determined by finger oxymetry, fell below 91% or "non-desaturaters" if SaO$ sb2$% remained above 91%. Subsequent determinations of the transfer capacity for CO (DLco) were made using a 3 second breath-hold technique (Gould 2400/2450), at rest as well as at 60% and 90% of previously determined VO$ sb2$ max ($>$4.0 1/min). The results show an increase in DLco from rest to the first exercise intensity (desat: 41.7 $ pm$ 5.7 to 55.1 $ pm$ 4.7; non-desat: 41.1 $ pm$ 5.8 to 57.2 $ pm$ 6.9 mlsCO/mmHg/min) without much further increase to the maximal workload (desat: 61.0 $ pm$ 6.0; non-desat: 61.4 $ pm$ 9.5 mls CO/mmHg/min). No significant differences in DLco were found between the two groups at rest or either of the two exercise intensities. Significant differences between the desat and non-desat groups were found for FVC, post-exercise FEF$ sb{25-75 %}$, and VE/VO$ sb2$. / The present results are in agreement with previous reports showing arterial desaturation in 50% of highly-trained subjects when VO$ sb2$ max $>$4.0 1/min. The present investigation cannot clearly establish the role of DLco in this response. (Abstract shortened by UMI.)

No description available.

No description available.

Viable tissue formation is often observed in peripheral regions of tissue engineering scaffolds whereas the interior fails to support viable tissue. This could be attributed to the fact that as cells within the pores of the scaffold begin to proliferate and secrete extracellular matrix, they simultaneously begin to occlude the pores and decrease supply of nutrients to the interior. Since transport within the scaffold is mainly a function of diffusion, careful design of the diffusion characteristics of the scaffold is critical. These transport issues relate to oxygen and nutrient delivery, waste removal, protein transport and cell migration, which in turn are governed by scaffold porosity and permeability. The current study addresses these issues by evaluating the effect of these architectural parameters on oxygen concentration and cell behavior in the interior of scaffolds with different architectures. Cylindrical polycaprolactone (PCL) scaffolds fabricated using precision extrusion deposition and having the same pore size but different porosities and tortuosities, and hence different permeabilities, were statically seeded with MG63 cells. The bases of the scaffolds were sealed with an impermeable layer of PCL and the scaffolds were surrounded with a tubing of low air permeability to allow diffusion of air into the constructs mainly from the top. These constructs were evaluated at days 1 and 7 for cell viability and proliferation as well as oxygen concentration as a function of depth within the construct. A simple mathematical model was used to describe the process of diffusion of oxygen in these cell-seeded scaffolds of varying permeability. It was hypothesized that there would be better diffusion and cell function with increasing permeability. This was found to be true in case of cell viability. However, cell proliferation data revealed no significant differences as a function of depth, day or architecture. Oxygen concentration data revealed trends showing decreasing concentrations of oxygen as a function of depth across all architectures. Tortuosity had a greater influence on oxygen concentration profiles on day 1 compared to porosity, whose effect seemed to dominate on day 7. Overall, porosity seemed to play a greater role than tortuosity in supporting viability, proliferation and oxygen diffusion. / text

Elite milers, Sir Roger Bannister and Joseph Falcon, have stated that the consumption of carbonated beverages hinders the performance of aerobic events. Oxygen transport is purportedly impaired by the consumption of carbonated beverages. The research on carbonated beverages has been limited to the effects on the digestive system, gastric emptying, and thermal heat stress in animals. The purpose of this study was to investigate the effects of consuming 28 ounces of carbonated beverages per day, for three weeks, on arterial oxygen saturation (Sa0₂), serum hemoglobin concentrations (Hb), and maximal oxygen consumption (VO₂max) in experienced cyclists. Nine competitive cyclists and triathletes (aged 19-24 years, M = 21.67 years), with average weights and percent body fat of 76.51 kg and 11.4 percent respectively, were randomly assigned to a three week period of consuming 28 ounces of carbonated water or a three week period of no carbonated beverages. At the end of each three week period, a 5 c.c. blood sample was taken for Hb determination and the subjects performed a test of maximal oxygen consumption on a cycle ergometer while Sa0₂ was being monitored. The groups then crossed-over with respect to their treatment, and after another three week period, the same variables were measured. The Student's t statistic was used to compare Sa0₂, Hb, and VO₂max. The results showed no significant differences between the carbonated period (C) and the noncarbonated period (NC) in Sa0₂ (94.00 vs 93.22 %, p= 0.21), Hb (13.71 vs 14.12 g/dl, p= 0.11), and VO₂max (4.63 vs 4.65 Imin, p= 0.92). From this study, it appears that the consumption of carbonated beverages does not affect the variables associated with the oxygen carrying capacity of blood (Sa0₂ and Hb) or the test of aerobic performance (V0₂max) / Graduation date: 1992

The purpose of this study was to examine the vertical component of the American College of Sports Medicine (A.C.S.M.) Guidelines equation to predict the oxygen cost of grade running. The A.C.S.M. Guidelines equation is: VO$ sb2$(ml/kg.min) = 3.5 + 0.2 speed(m/min) + 0.9 (speed(m/min) * grade(frac)). Twenty-three female runners (20 to 33 years) participated in (1) a VO$ sb2$max test, (2) five 6 min running economy (RE) tests at 133 m/min, (3) five 6 min RE tests at 160 m/min, and (4) three 6 min RE tests at 186 m/min. The RE tests at 133 and 160 m/min were performed at the following grades: 0, 2.5, 5.0, 7.5, and 10.0%. The RE tests at 186 m/min were performed at 0, 2.5, and 5.0% grade. The RE tests were administered in random order. There was a linear relationship between VO$ sb2$ and horizontal running velocity with a slope of 0.20 ml/kg.m (r = 0.996; p $<$.01). There was a linear relationship between VO$ sb2$ and percent grade when running on a treadmill. The correlations for the regression equations at speeds of 133, 160, and 186 m/min were 0.90 (p $<$.01), 0.86 (p $<$.01), and 0.73 (p $<$.01), respectively. Inclusion of a grade component in the regression analysis equation increased the accuracy for predicting the VO$ sb2$ of grade running. VO$ sb2$ consumption for grade running can be predicted using the following equation: VO$ sb2$ (ml/kg.min) = 3.5 + 0.198(speed in m/min + 0.932 grade(%)) + 0.006(speed(m/min) * grade(%)). The new equation explained 99.5% of the variance (R$ sp2$) compared to the 78.0% of the variance (R$ sp2$) that was explained by the A.C.S.M. Guidelines equation.

Exercise prescription intensity is traditionally defined using a target heart rate (HR) as a surrogate measure of oxygen uptake (V02). The ACSM Guidelines recommends the use of a percentage of the maximal HRR because it is thought to match a similar percentage of maximal V02 (%V02max). However, several recent studies have challenged the notion that a given percentage of MHRR matches with the same percentage of V02max in older subjects. The purpose of this study was to assess the difference between percentages of MHRR and V02ma, and evaluate the influence of age on the agreement between these two variables across a range of exercise intensities. The sample included 530 subjects (232 men and 298 women, mean ages of 46.6 + 11.7 years and 43.3 + 11.3 years respectively) who completed a maximal treadmill test to volitional fatigue using the BSU/Bruce Ramp protocol. Heart rate and V02 data from minutes 3, 6, and 9 were converted into percentages of MHRR and V02mai,. Subjects were excluded from the analysis if they failed to achieve an RER,„a,,>1.0. Minutes 3, 6, and 9 represented 45.2 ± 11, 66.0 ± 15, and 83.1 ± 12% of VO2.x, respectively. A one-way ANOVA showed that statistically significant differences existed between the treatment means of relative intensity at minutes 3, 6, and 9 at a p-value of <0.05. The influence of age was assessed by correlation with the difference between percentages of MHRR and VO2max at minutes 3, 6, and 9. In addition, younger (<60 years of age) and older (>60 years of age) subjects were compared using an unpaired t-test. The association between age and the difference between percentages of HRR and VO2max were -0.24, -0.22, and - 0.26 at minutes 3, 6, and 9, respectively. The difference in the relative intensities of HRR and VO2max was greater for older subjects at minutes 3 and 6 (-7.0 vs. -2.2, -3.2 vs. -0.8%) but was smaller at minute 9 (-0.1 vs. -3.2%). A Scheffe post-hoc analysis was used to compare the differences between the treatment means of relative intensity. In conclusion, these results confirm the notion that percentages of MHRR. tend to underestimate percentages of VO2max in older subjects, however the differences observed within the present study were smaller than those reported previously. The small but statistically differences between the techniques would not appear to invalidate the use of percentages of MHRR as surrogate markers of percentages of VO2max in these subjects. / School of Physical Education