Physiological effects of repeated exercise.
TL;DR: In large scale population studies of work capacity or in the evaluation of training programmes in rehabilitation studies, a continuous test may be used but attention must be paid to familiarization procedures.
Abstract: SUMMARY 1. The physiological responses to repeated continuous (progressive) exercise together with the relationship between continuous and discontinuous work tests on an upright bicycle ergometer have been studied in healthy male subjects. 2. The results show a marked decline in mean cardiac frequency (fH) from 145 beats/ min to 124 beats/min during the first four experiments at a given submaximal oxygen intake of 1.5 l/min and thereafter a smaller decline to reach 118 beats/min on the final (sixteenth) day of the investigation. This latter decrease was associated with a small but significant rise in maximum oxygen intake @02 max) which occurred from Day 8 onwards. Pulmonary minute ventilation at an oxygen intake of 1.5 l/min PE decreased by about 5 l/min immediately following the first occasion of submaximal work but thereafter remained unchanged. There was however no decrease in 0, cost of exercise, as 00, at a ked rate of external work remained unchanged throughout the investigation. 3. At maximal effort there was no significant decrease in either vEmax or fHmax, but the fH at which the 00, max was reached declined significantly from Day 8. Thus the asymptotic nature of the fH/002 curve which was very pronounced on Day 1 virtually disappeared following the third visit to the laboratory. The accuracy of predicting 00, max from fH and 00, increased noticeably from - 15.4 & 8.9% on Day 1 to - 6.5 10.5% on Day 7 and - 0.9 3.4% on Day 15. The possible physiological basis and implications of the results are discussed. 4. No significant differences were found between continuous and discontinuous work. Thus in large scale population studies of work capacity or in the evaluation of training programmes in rehabilitation studies, a continuous test may be used but attention must be paid to familiarization procedures. At least three preliminary test periods are necessary before the results become reproducible and reliable.
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TL;DR: Whether a VO2 plateau was consistently manifest during maximal incremental ramp cycle ergometry and the relationship between this peak VO2 (V(O2 peak) and that determined from one, or several, maximal constant-load tests is ascertained and the peak value attained was not different from the plateau in the plot of VO2 vs. work rate.
Abstract: The quantification of maximum oxygen uptake (Vo2 max), a parameter characterizing the effective integration of the neural, cardiopulmonary, and metabolic systems, requires oxygen uptake (Vo2) to ...
438 citations
TL;DR: It is concluded that ventilatory muscle training in patients with COPD improved the ventilatories muscle performance, as indicated by the increasedMSVC, oxygen consumption during the MSVC, and the maximal exercise ventilation.
Abstract: We examined the effect of a 6-wk period of ventilatory muscle endurance training on the maximal sustained ventilatory capacity (MSVC) and on exercise tolerance in 10 patients with chronic obstructive pulmonary disease (COPD). No significant changes occurred in lung volumes or spirometric indices. After training, the MSVC increased from 32 +/- 11 to 42 +/- 13 l/min (P less than 0.001) and the MSVC/FEV1 ratio from 40.2 +/- 8.8 to 47.8 +/- 8.0 (P less than 0.001). Oxygen consumption during the MSVC increased from 460 +/- 94 to 647 +/- 107 ml/min (P less than 0.001), and MSVC heart rate increased from 99 +/- 15 to 114 +/- 15 (P less than 0.001). The post MSVC blood lactate increased from 1.55 +/- 1.29 to 2.85 +/- 1.05 mM/l (P less than 0.001). Maximal exercise ventilation measured by an incremental ergometer test increased from 32 +/- 8 to 36 +/- 11.5 l/min for leg exercise and from 30.4 +/- 8.4 to 33.7 +/- 8.9 l/min (P less than 0.01) for arm exercise. Endurance time at a constant submaximal load increased from 6.98 +/- 4.30 to 10.76 +/- 6.00/min (P less than 0.01) for leg exercise and from 5.76 +/- 3.53 to 10.47 +/- 6.57/min (P less than 0.01) for arm exercise. The maximal distance covered in a 12-min walk increased from 1,058 +/- 161 to 1,188 +/- 201 m (P less than 0.01). We concluded that ventilatory muscle training in patients with COPD improved the ventilatory muscle performance, as indicated by the increased MSVC, oxygen consumption during the MSVC, and the maximal exercise ventilation. There was a substantial increase in submaximal exercise endurance for both arm and leg work.
193 citations
TL;DR: While there is some specificity of training when conditioning is based upon small muscle groups, treadmill training apparently improves cardiac performance, and thus V̇O2max, in many other types of endurance activity, which varies with the type of exercise.
Abstract: Synopsis: The determinants of endurance effort vary, depending upon the extent of the muscle mass that is activated. Large muscle work, such as treadmill running, is halted by impending circulatory failure; lack of venous return may compound the bask problem of an excessive cardiac work-load. If the task calls for use of a smaller muscle mass, there is ultimately difficulty in perfusing the active muscles, and glycolysis is halted by an accumulation of acid metabolites. Simple field tests of endurance, such as Cooper’s 12-minute run and the Canadian Home Fitness Test, have some value in the rapid screening of large populations, but like other submaximal tests of human performance they lack the precision needed to advise the individual. The directly measured maximum oxygen intake (VO2max) varies with the type of exercise. The highest values are obtained during uphill treadmill running, but well trained athletes often approach these values during performance of sport-specific tasks. Limitations of methodology and wide interindividual variations of constitutional potential limit the interpretation of maximum oxygen intake data in terms of personal fitness, exercise prescription and the monitoring of training responses. The main practical value of VO2max measurement is in the functional assessment of patients with cardiorespiratory disease, since changes are then large relative to the precision of the test. Determinants of Endurance Effort: During treadmill exercise, maximum effort is halted by central circulatory failure. It is less clear whether the limitation is imposed by a deficiency of venous return or an inability of the heart to develop an adequate stroke volume in the face of a rising peripheral resistance. Activities that depend upon the use of a relatively small muscle group (e.g. cycle ergometry, and especially arm ergometry) undoubtedly have some peripheral limitation, but this reflects difficulty in perfusing vigorously contracting muscles rather than any problem with utilisation of oxygen by the active fibres. Evidence of a cellular limitation of effort offered by Kaijser (1970) is disputed. VO2max varies somewhat with the type of exercise, but this reflects the difficulty in perfusing small muscles rather than an intracellular enzyme deficiency. Variations of ambient pressure cause the changes of VO2max predicted for a circulatory limitation, if due allowance is made for possible limitation of exercise by CO2 poisoning. While there is some specificity of training when conditioning is based upon small muscle groups, treadmill training apparently improves cardiac performance, and thus VO2max, in many other types of endurance activity. Changes of maximum cardiac output induced by heat or (β-blocking drugs do not modify oxygen transport, but this is because a varying proportion of the total blood flow is directed to tissue other than muscle. Cooling reduces VO2max, but this could reflect a circulatory change rather than a lowering of tissue enzyme activity. Training increases the aerobic enzyme content of muscles, but the cellular response does not develop in parallel with VO2max; its main ’purpose’ is to encourage the utilisation of fat. Impending loss of consciousness undoubtedly reflects failing blood flow to the brain, but muscle weakness is due to an inhibition of glycolysis. Factors contributing to the latter include deficient oxygen transport, a slow diffusion oflactate and, to a lesser extent, an accumulation of hydrogen ions within the working tissue. Assessment of Endurance Performance: Simple field tests of endurance may help in screening large populations for the constitutionally well-endowed. Cooper’s 12-minute run is the best known ofthese procedures, and works reasonably well in highly motivated young adults. If the intent is to discover potential athletes, tests need to be event-specific. Moreover, in many activities (such as swimming) skill has a major impact on score. The Canadian Home Fitness Test is a simple stepping procedure, paced by a longplaying gramophone record. The safety of subjects is assured by preliminary questioning, an adequate warm-up and conservative submaximal pulse ceilings. Originally devised as a motivational tool, it can also be used to test fitness in the community, having about the same accuracy as other submaximal tests. The basic assumptions of most submaximal predictions of VO2max include a linear heart rate/oxygen consumption relationship, a known maximum heart rate, and a known mechanical efficiency. Systematic errors of up to 10%, and random errors of ± 10% limit the value of the information that can be obtained through such prediction procedures. Direct measurements of VO2max depend upon careful technique (both preparation of the patient and biological calibration of the equipment). Increasing use is now made of sport-specific techniques, e.g. a flume for swimmers, rowing ergometers or rowing tanks for oarsmen, and roller-mounted racing cycles for cycling enthusiasts. Well-trained performers usually approach their treadmill VO2max during performance of the sport-specific task. The treadmill is the most popular of laboratory testing devices. The cycle ergometer generally yields a smaller and peripherally limited VO2max. although it has the advantage that it is easier to make ancillary measurements on a seated subject. A maximum effort step test remains a useful possibility for field locations, while various forms of arm ergometer are available for the testing of wheelchair athletes. Given one preliminary attempt, most adult volunteers can reach a classical plateau of oxygen consumption. Attempts to characterise the quality of an individual’s effort on subsidiary maximal criteria remain problematical. If good technical assistance is not available, fitness can be judged from the endurance of a progressive treadmill protocol, although such tests must be carried to complete exhaustion of the subject. Details of test protocol are less important than might be imagined. Factors contributing to a large VO2max score include a preliminary warm-up, running rather than walking, and possibly a schedule of effort which is intermittent rather than continuous. Interpretation: For most purposes, data are best expressed per kg of body mass, although absolute units are preferred for some weight-supported sports. Unusual results call for a critical review of both the technique and the population sampling procedures. Wide interindividual variations of constitutional potential and limitations of methodology limit the value of fitness assessment in the individual. Test scores give some guidance in work classification but in many sports the element of skill is more important than a large maximum oxygen intake. At best, exercise prescriptions based on VO2max are crude, and they need fine tuning by the individual or the coach. Likewise, the training response is usually small relative to methodological errors, so that there is limited scope for VO2max as a means of monitoring conditioning. The greatest potential of endurance testing probably lies in the overall functional assessment of cardiorespiratory disease, since many clinical conditions give rise to a gross impairment of VO2max.
179 citations
TL;DR: A comprehensive review of the English literature was conducted to obtain descriptive statistical data representing over 23,000 independent subjects from 5 to 81 years old to identify negative linear and non-linear age factors, an ergometry factor, a fitness factor and a continent factor.
Abstract: In an attempt to reduce the confusion regarding reported effects of age upon maximal exercise heart rate (HR max), a comprehensive review of the English literature was conducted to obtain descriptive statistical data representing over 23,000 independent subjects from 5 to 81 years old. The data were split randomly into two data sets for independent regression analyses. HR max was the dependent variable while independent variables include: age, age2, age3, age4, sex, level of fitness, type of ergometer, exercise protocol, continent of residence, and race. After cross validation the data were pooled and reanalyzed. Additional validation was accomplished on identifiable subsets of the data, e.g., cross sectional, longitudinal, training, comparative ergometry, and comparative sex studies. Results identified negative linear and non-linear age factors, an ergometry factor, a fitness factor and a continent factor. Age accounted for about 70–75% of the variability. Generalized equations were proposed. Ev...
143 citations
Journal Article•
TL;DR: It is argued that the validity of mental stress tests can be judged in relation to several different aspects, specifically, methodological, ecological, diagnostic, prognostic, and therapeutic validities.
Abstract: Many issues related to the selection, reliability, and validity of mental stress testing in cardiovascular research are discussed. Five categories of mental stress testing are distinguished: problem-solving tasks, information-processing tasks, psychomotor tasks, affective conditions, and aversive or painful conditions. A series of practical and theoretical criteria are outlined for the selection of appropriate tests, and the measurement of a range of dependent variables is emphasized. The temporal stability of cardiovascular responses to mental stress tests is examined through an analysis of test-retest correlations (weighted for sample size) in 28 comparisons with intervals between sessions varying from 1 day to more than 1 year. Heart rate reactions to tasks show an average-weighted Z of 0.732 +/- 0.031 (r = 0.62), with Z = 0.575 +/- 0.034 (r = 0.52) for systolic blood pressure and Z = 0.313 +/- 0.035 (r = 0.30) for diastolic blood pressure. It is argued that the validity of mental stress tests can be judged in relation to several different aspects, specifically, methodological, ecological, diagnostic, prognostic, and therapeutic validities. The nature of these standards is described, and pertinent literature is presented.
137 citations
References
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Journal Article•
1,609 citations
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01 Jan 1968
TL;DR: Lung function throughout life, structure, expansion and movement of the lung, andPhysiological aspects of treatment; and determinants and reference values.
Abstract: Preface. Acknowledgements. Early developments and future prospects.Terminology Basic equipment and methods.Lung function testing.general considerations.Structure, expansion and movement of the lung.Assessment of bellows and mechanical attributes of the lung.Distribution of ventilation and perfusion.Assessment of distribution of ventilation and blood flow.Exchange of gas in the lung.Measurement of transfer factor (diffusing capacity) and its subdivisions.Control of respiration.Assessment of respiratory control.Factors which limit exercise.Assessment of the physiological response to exercise.Lung function throughout life.determinants and reference values.Lung function in disease.Physiological aspects of treatment.Classified bibliography. Author Index. Subject.
863 citations
332 citations
TL;DR: During quiet breathing and in hyperpnoea there is a linear relation between pulmonary ventilation and tidal volume and parameter m, which is closely reproducible from day to day but differs from subject to subject and is positively correlated with the slope of the e ,P a CO2 response curve at high P a o2.
332 citations