During exercise below the lactate threshold (LT), the rate of adjustment (τ) of pulmonary O2 uptake (
) is slowed when initiated from a raised work rate. Whether this is consequent to the intrinsic ...properties of newly recruited muscle fibres, slowed circulatory dynamics or the effects of a raised metabolism is not clear. We aimed to determine the influence of these factors on
using combined in vivo and in silico approaches. Fifteen healthy men performed repeated 6 min bouts on a cycle ergometer with work rates residing between 20 W and 90% LT, consisting of the following: (1) two step increments in work rate (S1 and S2), one followed immediately by the other, equally bisecting 20 W to 90% LT; (2) two 20 W to 90% LT bouts separated by 30 s at 20 W to raise muscle oxygenation and pretransition metabolism (R1 and R2); and (3) two 20 W to 90% LT bouts separated by 12 min at 20 W allowing full recovery (F1 and F2). Pulmonary O2 uptake was measured breath by breath by mass spectrometry and turbinometry, and quadriceps oxygenation using near‐infrared spectroscopy. The influence of circulatory dynamics on the coupling of muscle and lung
was assessed by computer simulations. The
in R2 (32 ± 9 s) was not different (P > 0.05) from S2 (30 ± 10 s), but both were greater (P < 0.05) than S1 (20 ± 10 s) and the F control bouts (26 ± 10 s). The slowed
kinetics in R2 occurred despite muscle oxygenation being raised throughout, and could not be explained by slowed circulatory dynamics (
predicted by simulations: S1 = R2 < S2). These data therefore suggest that the dynamics of muscle O2 consumption are slowed when exercise is initiated from a less favourable energetic state.
Background One type of fecal occult blood test (FOBT), the unrehydrated guaiac fecal occult blood test (GT), is recommended by the United States Preventive Services Task Force and the Institute of ...Medicine for use in screening programs, but it has relatively low sensitivity as a single test for detecting advanced colonic neoplasms (cancer and adenomatous polyps ≥1 cm in diameter). Thus, improving the sensitivity of FOBT should make colon cancer screening programs that use these tests more effective. Methods We assessed prospectively the performance characteristics of two newer FOBTs in 5841 subjects at average risk for colorectal cancer in a large group–model managed care organization. The tests evaluated included a sensitive GT, a fecal immunochemical test (FIT), and the combination of both tests. Patients with positive and negative test results were advised to have colonoscopy and sigmoidoscopy, respectively. Sensitivity and specificity for detecting advanced neoplasms in the left colon within 2 years after the FOBT screening were evaluated for the two tests administered separately and in combination. Results A total of 139 patients were diagnosed with advanced colorectal neoplasms (n = 14 cancers, n = 128 adenomas) within the 2 years following their initial FOBT screening. Sensitivity for detecting cancer was 81.8% (95% confidence interval CI = 47.8% to 96.8%) for the FIT alone and 64.3% (95% CI = 35.6% to 86.0%) for the sensitive GT and the combination test. Sensitivity for detecting advanced colorectal adenomas was 41.3% (95% CI = 32.7% to 50.4%) for the sensitive GT, 29.5% (95% CI = 21.4% to 38.9%) for the FIT, and 22.8% (95% CI =16.1% to 31.3%) for the combination test. Specificity for detecting cancer and adenomas was 98.1% (95% CI = 97.7% to 98.4%) and 98.4% (95% CI = 98.0% to 98.7%), respectively, for the combination test; 96.9% (95% CI = 96.4% to 97.4%) and 97.3% (95% CI = 96.8% to 97.7%), respectively, for the FIT; and 90.1% (95% CI = 89.3% to 90.8%) and 90.6% (95% CI = 89.8% to 91.4%), respectively, for the sensitive GT. Conclusions The FIT has high sensitivity and specificity for detecting left-sided colorectal cancer, and it may be a useful replacement for the GT.
ABSTRACT
A symbiotic relationship between the high‐ and low‐frequency transients in the Southern Hemisphere has been examined by using ECMWF analyses of 500 mb geopotential height and temperature ...fields over 9 winter seasons. The low‐frequency transients organize the high‐frequency eddies over the regions where low‐frequency westerly anomalies prevail, forming traveling storm tracks that move together with the low‐frequency waves. The high‐frequency eddies, in turn, reinforce the barotropic component of the low‐frequency waves while tending to diminish the baroclinic component of the low‐frequency waves. All of these findings give further credence to earlier results for the Northern Hemisphere. As a supplementary to the feedback analyses, the energetics analysis for the winter seasons in both the Northern and the Southern Hemispheres reveals that the forcing of the low‐frequency flow by the high‐frequency transients in the Southern Hemisphere is much stronger than in the Northern Hemisphere. The contribution of the stationary waves to maintenance of the low‐frequency flow through barotropic instability is significantly less in the Southern Hemisphere.
During exercise below the lactate threshold (LT), the rate of adjustment (τ) of pulmonary VO(2) uptake (τ) is slowed when initiated from a raised work rate. Whether this is consequent to the ...intrinsic properties of newly recruited muscle fibres, slowed circulatory dynamics or the effects of a raised metabolism is not clear. We aimed to determine the influence of these factors on τV(O(2)) using combined in vivo and in silico approaches. Fifteen healthy men performed repeated 6 min bouts on a cycle ergometer with work rates residing between 20 W and 90% LT, consisting of the following: (1) two step increments in work rate (S1 and S2), one followed immediately by the other, equally bisecting 20 W to 90% LT; (2) two 20 W to 90% LT bouts separated by 30 s at 20 W to raise muscle oxygenation and pretransition metabolism (R1 and R2); and (3) two 20 W to 90% LT bouts separated by 12 min at 20 W allowing full recovery (F1 and F2). Pulmonary O(2) uptake was measured breath by breath by mass spectrometry and turbinometry, and quadriceps oxygenation using near-infrared spectroscopy. The influence of circulatory dynamics on the coupling of muscle and τV(O(2)) lung was assessed by computer simulations. The τV(O(2)) in R2 (32 ± 9 s) was not different (P > 0.05) from S2 (30 ± 10 s), but both were greater (P < 0.05) than S1 (20 ± 10 s) and the F control bouts (26 ± 10 s). The slowed V(O(2)) kinetics in R2 occurred despite muscle oxygenation being raised throughout, and could not be explained by slowed circulatory dynamics (τV(O(2)) predicted by simulations: S1 = R2 < S2). These data therefore suggest that the dynamics of muscle O(2) consumption are slowed when exercise is initiated from a less favourable energetic state.
A symbiotic relationship between the high- and low-frequency transients in the Southern Hemisphere has been examined by using ECMWF analyses of 500 mb geopotential height and temperature fields over ...9 winter seasons. The low-frequency transients organize the high-frequency eddies over the regions where low-frequency westerly anomalies prevail, forming traveling storm tracks that move together with the low-frequency waves. The high-frequency eddies, in turn, reinforce the barotropic component of the low-frequency waves while tending to diminish the baroclinic component of the low-frequency waves. All of these findings give further credence to earlier results for the Northern Hemisphere. As a supplementary to the feedback analyses, the energetics analysis for the winter seasons in both the Northern and the Southern Hemispheres reveals that the forcing of the low-frequency flow by the high-frequency transients in the Southern Hemisphere is much stronger than in the Northern Hemisphere. The contribution of the stationary waves to maintenance of the low-frequency flow through barotropic instability is significantly less in the Southern Hemisphere.
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