Biomedical subjects

U Wisløff

Publications and source records attributed to U Wisløff.

22 records · Page 2Linked to original sources

PubMed1998

Methods for evaluating peak oxygen uptake and anaerobic threshold in upper body of cross-country skiers.

PURPOSE: The aim of the present study was to develop a standard protocol for evaluating peak oxygen uptake and anaerobic threshold during upper body work by cross-country skiers. METHODS: All tests were performed on a specially developed ski ergometer and incorporated the double poling technique. In series I, continuous and discontinuous protocols for measuring VO2peak at different inclinations of the ski ergometer were performed. In series II, a protocol for evaluating anaerobic threshold during upper body work was established. Eleven well trained regional male cross-country skiers participated in the study. All tests in each series were carried out during a period of 14 d. RESULTS: VO2peak did not differ using continuous or discontinuous protocol while working on the ski ergometer. Inclination was found to influence VO2peak, which was reduced at 7 degrees compared with 3 degrees, 5 degrees, and 6 degrees. Th(an) working on the ski ergometer was reached at a power output, VO2, or fc, which gave on average a blood lactate concentration of 1.8 mmol.L-1 higher than those found after the warm-up period during a graded protocol. CONCLUSIONS: Testing only the traditional Th(an) and VO2max while running on a treadmill hides important determinants of endurance in cross-country skiing as shown by that no correlation was found between VO2max and VO2peak in the present study.

Adult↗

PubMed1998

Evaluation of a new upper body ergometer for cross-country skiers.

A new specific ski ergometer has been developed to study aerobic endurance and force development in the upper body of cross-country skiers. The major purpose of the present study was to examine the validity and the reliability of this ergometer. Eleven male cross-country skiers participated in the study. Work on the ski ergometer, at an inclination of 4 degree, incorporated the double-poling technique. All subjects participated in three tests in addition to a pretest where peak oxygen uptake in the upper body (VO2peak) and maximal oxygen uptake during treadmill running (VO2max) were measured. In a field-test, subjects performed double poling uphill, and VO2peak was reached after 4-6 min. There was no statistically significant differences in power output (Watt) or oxygen uptake (VO2) at the same exercise stages between tests and the coefficient of variation was 2.0% and 2.5%, respectively. There were no significant differences between VO2peak as measured in the field and on the ski ergometer. The average upper body/leg ratio was 90% (range 78.1-97.1%). There was no significant correlation between VO2max and VO2peak. The present study showed the ski ergometer to be both reliable and valid for evaluating VO2 and force development in the upper body at submaximal and maximal workloads for cross-country skiers.

Adult↗

PubMedDate not supplied

Reduced pH and contractility in failing rat cardiomyocytes.

AIM: To determine whether reduced cardiomyocyte contractility in heart failure is associated with reduced intracellular pH (pH(i)). Involvement of the Na(+)/H(+) exchanger and the H(+)/K(+) ATPase were investigated with specific blockers. METHODS: Myocardial infarction and subsequent heart failure in Sprague-Dawley rats were induced by chronic occlusion of the left coronary artery. 6 weeks post-ligation, contractility (cell shortening) and pH(i) (BCECF fluorescence) were recorded in freshly dissociated cardiomyocytes during 2-10 Hz electrical stimulation, with or without either Na(+)/H(+) exchanger or H(+)/K(+) ATPase inhibition. RESULTS: Elevated end-diastolic and reduced peak systolic pressures confirmed heart failure. Increased heart weights (20-30%; P < or = 0.01) and cardiomyocyte lengths and widths (22-25%; P < or = 0.01) confirmed substantial cardiac hypertrophy. In myocytes isolated from sham operated rats, a positive staircase response occurred with stimulation rates from 2 to 7 Hz; further increases in stimulation rate up to 10 Hz reduced contractility. In contrast, pH(i) fell progressively over the entire stimulation range. In failing myocytes, pH(i) was consistently 0.07 pH units lower and contractility 40% lower (P < or = 0.01) than sham control values; the shape of the contractility staircase remained similar to controls. At all stimulation frequencies, Na(+)/H(+) exchanger inhibition reduced pH(i) by 0.05 pH units (P < or = 0.01) and contractility by 22% (P < or = 0.05) in cardiomyocytes from the heart failure group. A significantly smaller decrease of pH(i) and reduction in contractility was observed after inhibition of Na(+)/H(+) exchanger (10 micro m HOE694) in sham myocytes. H(+)/K(+) ATPase inhibition (100 micro m SCH28080) had no effect on pH(i). CONCLUSION: Reduced pH(i) is accompanied by reduced cardiomyocyte contractility in isolated myocytes from post-MI heart failure. The data suggest compensatory Na(+)/H(+) exchanger activation in heart failure, whereas H(+)/K(+) ATPase does not appear to contribute significantly to pH(i) maintenance.

Animals↗

PubMedDate not supplied

The effect of endurance training on the rate of nitrogen elimination in women.

INTRODUCTION: The rate of nitrogen elimination may be an important factor in evaluating the risk of DCS following dives. The present study determined the reproducibility of a method for evaluating nitrogen elimination (series I), and the effect of chronic training on the nitrogen elimination in healthy young women (series II). METHODS: Nitrogen elimination was determined with subjects wearing an AGA full-face mask breathing pure oxygen. To evaluate the reproducibility of the method for nitrogen elimination, three tests were performed in six subjects in series I. Nitrogen elimination in series II was measured before and after the training period. The training protocol (series II) consisted of interval training, three times per week for eight weeks. Four repeated intervals alternated between four minutes at 90-95% of maximum heart rate and three minutes at 50-60%. RESULTS: There was no significant difference between the three repeated tests. Interval training for eight weeks increased maximum oxygen uptake by 22.1%. Endurance training did not influence the total nitrogen elimination at rest. CONCLUSION: The method for evaluating nitrogen elimination at rest was found to be reproducible. Improved aerobic capacity does not increase the rate of nitrogen elimination at rest.

Adult↗