The John Sutton memorial lecture, 2009. Conductance systems: an integrative approach to the physiology of extreme conditions

2010 ◽  
Vol 35 (2) ◽  
pp. 113-124 ◽  
Author(s):  
Roy J. Shephard
Keyword(s):  
Sports Medicine ◽  
Blood Stream ◽  
Transport Processes ◽  
Integrative Approach ◽  
Memorial Lecture ◽  
Oxygen Intake ◽  
Maximal Oxygen Intake ◽  
Cardiorespiratory Function ◽  
Conductance Theory ◽  
Major Interest

This presentation explores the value of mechanical, electrical, and mathematical analogues in understanding and evaluating a variety of closely integrated transport processes in human biology. Particular attention is directed to a major interest of John Sutton: the factors limiting transport of oxygen from the atmosphere to the working muscles when exercising in a variety of hostile environments. In most circumstances, the limiting term in a closely linked chain of conductances seems to be in the blood stream, and its magnitude can be estimated by measurements of maximal oxygen intake. Despite recent criticisms of this index by those who have proposed a feed-forward control of maximal aerobic effort, conductance theory suggests that the main limitation of oxygen transport is normally maximal cardiac output. Therefore, careful laboratory determinations of maximal oxygen intake continue to provide a convenient integrating assessment of an individual’s cardiorespiratory function, with many important applications in sports medicine and exercise science.

POINT: Is it Time to Rethink Aerobic Exercise Prescription Methods?

2021 ◽  
Vol 10 (3) ◽  
pp. 94-96
Author(s):  
Carlo Ferri Marini ◽  
Francesco Lucertini ◽  
James S. Skinner
Keyword(s):  
Heart Rate ◽  
Aerobic Exercise ◽  
Sports Medicine ◽  
Exercise Prescription ◽  
Oxygen Intake ◽  
Advantages And Disadvantages

ABSTRACT Exercise prescription is complex and can vary greatly. As well, methods have their own advantages and disadvantages. The purpose of this discussion is to consider if some of these methods should be modified. We look at the concept of the heart rate and oxygen intake reserve because it is recommended by the American College of Sports Medicine.

Limitations to prediction of maximal oxygen intake

1964 ◽  
Vol 19 (5) ◽  
pp. 919-927 ◽  
Author(s):  
Loring B. Rowell ◽  
Henry L. Taylor ◽  
Yang Wang
Keyword(s):  
Metabolic Rate ◽  
Pulse Rate ◽  
Oxygen Intake ◽  
Physical Conditioning ◽  
Maximal Oxygen Intake ◽  
Before And After ◽  
Normal Men ◽  
Accuracy Of Prediction ◽  
Relationship Of ◽  
The Relationship

The predictability of maximal O2 intake (max Vo2) was studied in four groups of normal men, 18–24 years of age. Prediction of max Vo2 was made from pulse rate and Vo2 at a single submaximal workload at an ambient temperature of 78 F by use of the nomogram of Åstrand and Ryhming (1954) and underestimated actual max Vo2 by 27 ± 7% and 14 ± 7% in a sedentary group, before and after 2frac12–3 months of physical training, and by 5.6 ȁ 4% in a group of ten endurance athletes. Accuracy of prediction in all groups varied with approximation of pulse rate to 128 beats/min at 50% of max Vo2. Nonspecific stresses increased predictive errors in all groups. Constants b (slope) and A (intercept) in the regression equation Vo2 = bP – A (where P is pulse rate), were determined from Vo2 and pulse measured at four submaximal workloads requiring 13–28 ml O2/kg min. Prediction of max Vo2 by extrapolation of the slope to maximal pulse rate resulted in underestimation of 700–800 ml O2/min. Removal of 14% of circulating hemoglobin decreased max Vo2 by 4% but there was no change in pulse rates or predicted max Vo2. The relationship of RQ to V22 during work provided no reliable basis for prediction of max Vo2. exercise pulse rate, oxygen intake, relationship; pulse rate, oxygen intake relationship in exercise; metabolic rate, maximal aerobic prediction of; aerobic metabolic rate, maximal, prediction of; phlebotomy, effect on maximal oxygen intake, pulse rate; blood loss, effect on maximal oxygen intake, pulse rate; training, effect on maximal oxygen intake, pulse rates; physical conditioning, effect on maximal oxygen intake, pulse rates Submitted on October 4, 1963

scholarly journals Muscular exercise, lactic acid, and the supply and utilisation of oxygen. Part X.—The oxygen intake during exercise while breathing mixtures rich in oxygen

1925 ◽  
Vol 98 (689) ◽  
pp. 287-289 ◽  
Keyword(s):  
Normal Subjects ◽  
Simple Calculation ◽  
Oxygen Mixture ◽  
Oxygen Intake ◽  
Rubber Tubing ◽  
Atmospheric Air ◽  
Maximal Oxygen Intake ◽  
Douglas Bag ◽  
Expired Gas ◽  
Work Done

In the present series (Part VII) A. V. Hill, C. N. H. Long and H. Lupton* showed an interesting result with normal subjects, on the oxygen intake during exercise while breathing rich oxygen mixtures. They found that there is a considerable rise, reaching 50 per cent., in the maximal oxygen intake when breathing oxygen mixtures, as compared with breathing air; and, further, they calculated under such conditions the work done by the heart. This phenomenon has been re-observed, and some possible errors that might occur in the method are here discussed. The method used was that of the Douglas bag, and the expired air was analysed by the Haldane apparatus. The exercise was “standing-running”. The most serious error that might complicate or affect the results is that due to contamination, by air, of the expired gases. The following simple calculation is sufficient to show the large effect of such contamination by air if it occurred. Suppose that 118 litres of a 50 per cent. oxygen mixture be mixed with 2 litres of air; then calculate how much oxygen has apparently disappeared. The oxygen in 120 litres of the new mixture is 118 × 0·5 + 2 × 0·2 = 59·4 litres, so that the oxygen percentage is now 49·5 per cent. Thus, assuming equality of the inspired and expired nitrogen, apparently about 1 per cent. of oxygen has disappeared, i.e. about 1·2 litres of oxygen corresponding to the 120 litres of expired gas. Now assume that a subject records a ventilation of 120 litres per minute and a maximal oxygen intake of 3·8 litres breathing atmospheric air; and that no rise in the oxygen intake actually occurs, when breathing a rich oxygen mixture, but that 120 litres of apparently expired gas now consist of 118 litres of actual expired gas and 2 litres of air leaked in. The result obtained in such an experiment uld give an apparent oxygen intake of 5·0 litres per minute. The following experiments, therefore, were performed with every possible care taken to avoid leakage. The mouthpieces were tested and found to be air-tight, while the Douglas bag and the corrugated rubber tubing were carefully washed with oxygen mixture. Special attention was paid to any possible leakage round the mouth, since the breathing is so heavy that there would appear to be a risk of sucking air inwards.

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